Title: Effect of leg immersion in mild warm carbonated water on skin and muscle blood flow

Authors: Ogoh S, Washio T, Suzuki K, Ikeda K, Hori T, Olesen ND, Muraoka Y.

Journal: Physiol Rep. 2018 Sep;6(18):e13859. doi: 10.14814/phy2.13859. PMID: 30221833; PMCID: PMC6139710.

Link to full text: Effect of leg immersion in mild warm carbonated water on skin and muscle blood flow

Abstract: Leg immersion in carbonated water improves endothelial-mediated vasodilator function and decreases arterial stiffness but the mechanism underlying this effect remains poorly defined. We hypothesized that carbonated water immersion increases muscle blood flow. To test this hypothesis, 10 men (age 21 ± 0 years; mean ± SD) underwent lower leg immersion in tap or carbonated water at 38°C. We evaluated gastrocnemius muscle oxyhemoglobin concentration and tissue oxygenation index using near-infrared spectroscopy, skin blood flow by laser Doppler flowmetry, and popliteal artery (PA) blood flow by duplex ultrasound. Immersion in carbonated, but not tap water elevated PA (from 38 ± 14 to 83 ± 31 mL/min; P < 0.001) and skin blood flow (by 779 ± 312%, P < 0.001). In contrast, lower leg immersion elevated oxyhemoglobin concentration and tissue oxygenation index with no effect of carbonation (P = 0.529 and P = 0.495). In addition, the change in PA blood flow in response to immersion in carbonated water correlated with those of skin blood flow (P = 0.005) but not oxyhemoglobin concentration (P = 0.765) and tissue oxygenation index (P = 0.136) while no relations was found for tap water immersion. These findings indicate that water carbonation has minimal effect on muscle blood flow. Furthermore, PA blood flow increases in response to lower leg immersion in carbonated water likely due to a large increase in skin blood flow.

Title: Carbonate Ion-Enriched Hot Spring Water Promotes Skin Wound Healing in Nude Rats

Authors: Liang J, Kang D, Wang Y, Yu Y, Fan J, Takashi E.

Journal: PLoS One. 2015 Feb 11;10(2):e0117106. doi: 10.1371/journal.pone.0117106. PMID: 25671581; PMCID: PMC4324962.

Link to full text: Carbonate Ion-Enriched Hot Spring Water Promotes Skin Wound Healing in Nude Rats

Abstract: Hot spring or hot spa bathing (Onsen) is a traditional therapy for the treatment of certain ailments. There is a common belief that hot spring bathing has therapeutic effects for wound healing, yet the underlying molecular mechanisms remain unclear. To examine this hypothesis, we investigated the effects of Nagano hot spring water (rich in carbonate ion, 42°C) on the healing process of the skin using a nude rat skin wound model. We found that hot spring bathing led to an enhanced healing speed compared to both the unbathed and hot-water (42°C) control groups. Histologically, the hot spring water group showed increased vessel density and reduced inflammatory cells in the granulation tissue of the wound area. Real-time RT-PCR analysis along with zymography revealed that the wound area of the hot spring water group exhibited a higher expression of matrix metalloproteinases-2 and -9 compared to the two other control groups. Furthermore, we found that the enhanced wound healing process induced by the carbonate ion-enriched hot spring water was mediated by thermal insulation and moisture maintenance. Our results provide the evidence that carbonate ion-enriched hot spring water is beneficial for the treatment of skin wounds.

Title: The effect of transcutaneous application of carbon dioxide (CO2) on skeletal muscle

Authors: Oe K, Ueha T, Sakai Y, Niikura T, Lee SY, Koh A, Hasegawa T, Tanaka M, Miwa M, Kurosaka M.

Journal: Biochem Biophys Res Commun. 2011 Apr 1;407(1):148-52. doi: 10.1016/j.bbrc.2011.02.128. Epub 2011 Mar 1. PMID: 21371433.

Link to Pubmed: The effect of transcutaneous application of carbon dioxide (CO2) on skeletal muscle

Abstract: In Europe, carbon dioxide therapy has been used for cardiac disease and skin problems for a long time. However there have been few reports investigating the effects of carbon dioxide therapy on skeletal muscle. Peroxisome proliferators-activated receptor (PPAR)-gamma coactivator-1 (PGC-1α) is up-regulated as a result of exercise and mediates known responses to exercise, such as mitochondrial biogenesis and muscle fiber-type switching, and neovascularization via up-regulation of vascular endothelial growth factor (VEGF). It is also known that silent mating type information regulation 2 homologs 1 (SIRT1) enhances PGC-1α-mediated muscle fiber-type switching. Previously, we demonstrated transcutaneous application of CO2 increased blood flow and a partial increase of O2 pressure in the local tissue known as the Bohr effect. In this study, we transcutaneously applied CO2 to the lower limbs of rats, and investigated the effect on the fast muscle, tibialis anterior (TA) muscle. The transcutaneous CO2 application caused: (1) the gene expression of PGC-1α, silent mating type information regulation 2 homologs 1 (SIRT1) and VEGF, and increased the number of mitochondria, as proven by real-time PCR and immunohistochemistry, (2) muscle fiber switching in the TA muscle, as proven by isolation of myosin heavy chain and ATPase staining. Our results suggest the transcutaneous application of CO2 may have therapeutic potential for muscular strength recovery resulting from disuse atrophy in post-operative patients and the elderly population.

Title: Topical cutaneous application of carbon dioxide via a hydrogel for improved fracture repair: results of phase I clinical safety trial

Authors: Niikura T, Iwakura T, Omori T, Lee SY, Sakai Y, Akisue T, Oe K, Fukui T, Matsushita T, Matsumoto T, Kuroda R.

Journal: BMC Musculoskelet Disord. 2019 Nov 25;20(1):563. doi: 10.1186/s12891-019-2911-7. PMID: 31766994; PMCID: PMC6878668.

Link to full text: Topical cutaneous application of carbon dioxide via a hydrogel for improved fracture repair: results of phase I clinical safety trial

Abstract: Background: Clinicians have very limited options to improve fracture repair. Therefore, it is critical to develop a new clinically available therapeutic option to assist fracture repair biologically. We previously reported that the topical cutaneous application of carbon dioxide (CO2) via a CO2 absorption-enhancing hydrogel accelerates fracture repair in rats by increasing blood flow and angiogenesis and promoting endochondral ossification. The aim of this study was to assess the safety and efficacy of CO2 therapy in patients with fractures. Methods: Patients with fractures of the femur and tibia were prospectively enrolled into this study with ethical approval and informed consent. The CO2 absorption-enhancing hydrogel was applied to the fractured lower limbs of patients, and then 100% CO2 was administered daily into a sealed space for 20 min over 4 weeks postoperatively. Safety was assessed based on vital signs, blood parameters, adverse events, and arterial and expired gas analyses. As the efficacy outcome, blood flow at the level of the fracture site and at a site 5 cm from the fracture in the affected limb was measured using a laser Doppler blood flow meter. Results: Nineteen patients were subjected to complete analysis. No adverse events were observed. Arterial and expired gas analyses revealed no adverse systemic effects including hypercapnia. The mean ratio of blood flow 20 min after CO2 therapy compared with the pre-treatment level increased by approximately 2-fold in a time-dependent manner. Conclusions: The findings of the present study revealed that CO2 therapy is safe to apply to human patients and that it can enhance blood flow in the fractured limbs.

Title: Breathing Practices for Stress and Anxiety Reduction: Conceptual Framework of Implementation Guidelines Based on a Systematic Review of the Published Literature

Authors: Bentley TGK, D’Andrea-Penna G, Rakic M, Arce N, LaFaille M, Berman R, Cooley K, Sprimont P.

Journal: Brain Sciences. 2023; 13(12):1612. https://doi.org/10.3390/brainsci13121612

Link to full text: Breathing Practices for Stress and Anxiety Reduction: Conceptual Framework of Implementation Guidelines Based on a Systematic Review of the Published Literature

Abstract: Anxiety and stress plague populations worldwide. Voluntary regulated breathing practices offer a tool to address this epidemic. We reviewed the peer-reviewed published literature to evaluate practice components associated with stress reduction effectiveness. We identified 58 clinical studies, comprising 41 RCTs and 17 single-arm, pre-post, non-randomized trials; 5407 total participants were included, with a mean age of 35.9 years and 43.92% female. Among the 72 included interventions, breathing practices significantly reduced stress/anxiety in 54 interventions. Findings were used to develop a conceptual framework of breath practice effectiveness. While commonly emphasized factors such as specific breath pace, population, and group versus individual practice were not found to be associated with effectiveness, five core components were: avoiding fast-only and <5 min practices; and incorporating human-guided training during initial sessions, multiple sessions, and long-term practice. Following this simple, evidence-based framework can help maximize the stress reduction benefits of breathing practices among broad populations.

Title: Slow-Breathing Curriculum for Stress Reduction in High School Students: Lessons Learned From a Feasibility Pilot

Authors: Bentley TGK, Seeber C, Hightower E, Mackenzie B, Wilson R, Velazquez A, Cheng A, Arce NN, Lorenz KA.

Journal: Front Rehabil Sci. 2022 Jul 1;3:864079. doi: 10.3389/fresc.2022.864079. PMID: 36189008; PMCID: PMC9397716.

Link to full text: Slow-Breathing Curriculum for Stress Reduction in High School Students: Lessons Learned From a Feasibility Pilot

Abstract: Purpose: Nearly one in three US adolescents meet the criteria for anxiety, an issue that has worsened with the COVID-19 pandemic. We developed a video-based slow diaphragmatic breathing stress-reduction curriculum for high school students and evaluated its feasibility, tolerability, and preliminary effectiveness. Methods: This cluster-randomized feasibility pilot compared 5-min slow diaphragmatic breathing for 5 weeks with treatment-as-usual control among four 12th-grade public high school classes. Students individually participated after school during COVID-19-related hybrid teaching, with slow diaphragmatic breathing three times/week and breath science education once/week. Feasibility was based on completion of breathing exercises, breath science education, and preliminary effectiveness assessments, and ease/tolerability was based on qualitative assessments. Results: Forty-three students consented to participate. Breath practice compliance ranged from 29 to 83% across classes and weeks, and decreased on average over the 5 weeks. Compliance with the breath science videos ranged from 43 to 86%, and that with the weekly STAI-State and CO2TT measures varied from 36 to 86%. Compliance with ease/tolerability assessments ranged from 0 to 60%. Preliminary effectiveness assessments' compliance varied across classes from 83 to 89% during baseline, and 29 to 72% at follow-up. The curriculum was rated as somewhat-to-definitely useful/beneficial, and definitely-to-very easy/tolerable. Students reported enjoying the diaphragmatic breathing, CO2TT, and breath science education; some found the extended exhales challenging and the curriculum and assessments time-consuming. Preliminary effectiveness analyses indicated no significant changes in STAI or CO2TT from baseline to followup or from before to after breathing exercises (p > 0.05 for all). Conclusions: Implementation of this 5-week slow breathing curriculum was feasible and tolerable to this cohort. Compliance, tolerability, and effectiveness may be improved with in-class participation. Future research on simple and accessible slow-breathing exercises is warranted to address today's adolescent stress-management crisis.

Title: Humans without a sense of smell breathe differently

Authors: Gorodisky, L., Honigstein, D., Weissbrod, A. et al.

Journal: Nat Commun 15, 8809 (2024). https://doi.org/10.1038/s41467-024-52650-6

Link to full text: Humans without a sense of smell breathe differently

Abstract: Olfaction may play a restricted role in human behavior, yet paradoxically, its absence in anosmia is associated with diverse deleterious outcomes, culminating in reduced life expectancy. The mammalian nose serves two purposes: olfaction and breathing. Because respiratory patterns are impacted by odors, we hypothesized that nasal respiratory airflow may be altered in anosmia. We apply a wearable device that precisely logs nasal airflow for 24-hour-long sessions in participants with isolated congenital anosmia and controls. We observe significantly altered patterns of respiratory nasal airflow in anosmia in wake and in sleep. These differences allow classification of anosmia at 83% accuracy using the respiratory trace alone. Patterns of respiratory airflow have pronounced impact on health, emotion and cognition. We therefore suggest that a portion of the deleterious outcomes associated with anosmia may be attributed to altered patterns of respiratory nasal airflow rather than a direct result of lost odor perception per se.

Title: Improved exercise ventilatory efficiency with nasal compared to oral breathing in cardiac patients

Authors: Eser P, Calamai P, Kalberer A, Stuetz L, Huber S, Kaesermann D, Guler S, Wilhelm M.

Journal: Front Physiol. 2024 Aug 6;15:1380562. doi: 10.3389/fphys.2024.1380562.PMID: 39165283; PMCID: PMC11334221.

Link to full text: Improved exercise ventilatory efficiency with nasal compared to oral breathing in cardiac patients

Abstract: Objectives: To assess whether nasal breathing improves exercise ventilatory efficiency in patients with heart failure (HF) or chronic coronary syndromes (CCS). Background: Exercise inefficient ventilation predicts disease progression and mortality in patients with cardiovascular diseases. In healthy people, improved ventilatory efficiency with nasal compared to oral breathing was found. Methods: Four study groups were recruited: Patients with HF, patients with CCS, old (age≥45 years) and young (age 20-40 years) healthy control subjects. After a 3-min warm-up, measurements of 5 min with once nasal and once oral breathing were performed in randomized order at 50% peak power on cycle ergometer. Ventilation and gas exchange parameters measured with spiroergometry were analysed by Wilcoxon paired-sample tests and linear mixed models adjusted for sex, height, weight and test order. Results: Groups comprised 15 HF, CCS, and young control and 12 old control. Ventilation/carbon dioxide production (V E/V CO2), ventilation (V E), breathing frequency (fR), and end-tidal oxygen partial pressure (PETO2) were significantly lower and tidal volume and end-tidal carbon dioxide partial pressure (PETCO2) significantly higher during nasal compared to oral breathing in all groups, with large effect sizes for most parameters. For patients with HF, median V E/V CO2 was 35% lower, fR 26% lower, and PETCO2 10% higher with nasal compared to oral breathing, respectively. Exercise oscillatory ventilation (EOV) was present in 6 patients and markedly reduced with nasal breathing. Conclusion: Nasal breathing during submaximal exercise significantly improved ventilatory efficiency and abnormal breathing patterns (rapid shallow breathing and EOV) in 80% of our patients with HF and CCS.

Title: Effects of conscious connected breathing on cortical brain activity, mood and state of consciousness in healthy adults

Authors: Bahi, C., Irrmischer, M., Franken, K. et al.

Journal: Curr Psychol 43, 10578–10589 (2024). https://doi.org/10.1007/s12144-023-05119-6

Link to full text: Effects of conscious connected breathing on cortical brain activity, mood and state of consciousness in healthy adults

Abstract: Breathwork as a means of inducing non-ordinary states of consciousness is gaining traction as a potential therapeutic modality. We examined the effects of breathwork (in the form of connected breathing) on electroencephalography (EEG) and mood in 20 healthy participants (aged between 23 and 39 years (female = 11, Mage = 29). In addition, to compare with other means of inducing non-ordinary states of consciousness, we assessed the subjective effects of breathwork using the 11 Dimension Altered State of Consciousness questionnaire. EEG spectral power analysis of eyes closed rest recordings before and after the breathwork session showed a decrease in delta (1–4 Hz) and theta (4–8 Hz) frequencies in frontotemporal and parietal regions, respectively no changes were seen in Alpha (9–12 Hz) and Beta (12–30 Hz) bands. However, after decomposing the beta waves in Beta 1 (12–15 Hz), Beta 2 (15–20 Hz), Beta 3 (20–30 Hz), decreases in power were observed across Beta1 and Beta 2 in parietotemporal regions. Notably, the spectral power in gamma increased in experienced practitioners. Scores on the Profile of Mood States questionnaire showed a reduction in negative affect (anger, tension, confusion, and depression) and an increase in esteem. Scores on the 11D-ASC scale indicated that subjective experiences during breathwork were similar to those after medium to high doses of psilocybin, suggesting the occurrence of experiences of mystical quality. Present results indicate that breathwork changes brain activity and mood, and induces mystical experiences. These results are promising and suggest that such techniques could be useful to improve mental well-being.

Title: Dismantling the Component-Specific Effects of Yogic Breathing: Feasibility of a Fully Remote Three-Arm RCT with Virtual Laboratory Visits and Wearable Physiology.

Authors: Ma Y, Yang H, Vazquez M, Buraks O, Haack M, Mullington JM, Goldstein MR.

Journal: Int J Environ Res Public Health. 2023 Feb 11;20(4):3180. doi: 10.3390/ijerph20043180. PMID: 36833875; PMCID: PMC9958552.

Link to full text: Dismantling the Component-Specific Effects of Yogic Breathing: Feasibility of a Fully Remote Three-Arm RCT with Virtual Laboratory Visits and Wearable Physiology.

Abstract: Despite the growing research base examining the benefits and physiological mechanisms of slow-paced breathing (SPB), mindfulness (M), and their combination (as yogic breathing, SPB + M), no studies have directly compared these in a ”dismantling” framework. To address this gap, we conducted a fully remote three-armed feasibility study with wearable devices and video-based laboratory visits. Eighteen healthy participants (age 18–30 years, 12 female) were randomized to one of three 8-week interventions: slow-paced breathing (SPB, N = 5), mindfulness (M, N = 6), or yogic breathing (SPB + M, N = 7). The participants began a 24-h heart rate recording with a chest-worn device prior to the first virtual laboratory visit, consisting of a 60-min intervention-specific training with guided practice and experimental stress induction using a Stroop test. The participants were then instructed to repeat their assigned intervention practice daily with a guided audio, while concurrently recording their heart rate data and completing a detailed practice log. The feasibility was determined using the rates of overall study completion (100%), daily practice adherence (73%), and the rate of fully analyzable data from virtual laboratory visits (92%). These results demonstrate feasibility for conducting larger trial studies with a similar fully remote framework, enhancing the ecological validity and sample size that could be possible with such research designs.

Title: Breathwork interventions for adults with clinically diagnosed anxiety disorders: A scoping review

Authors: Banushi B, Brendle M, Ragnhildstveit A, et al.

Journal: Brain Sci. 2023 Feb 2;13(2):256. doi: 10.3390/brainsci13020256. PMID: 36831799; PMCID: PMC9954474.

Link to full text: Breathwork interventions for adults with clinically diagnosed anxiety disorders: A scoping review

Abstract: Anxiety disorders are the most common group of mental disorders, but they are often underrecognized and undertreated in primary care. Dysfunctional breathing is a hallmark of anxiety disorders; however, mainstays of treatments do not tackle breathing in patients suffering anxiety. This scoping review aims to identify the nature and extent of the available research literature on the efficacy of breathwork interventions for adults with clinically diagnosed anxiety disorders using the DSM-5 classification system. Using the PRISMA extension for scoping reviews, a search of PubMed, Embase, and Scopus was conducted using terms related to anxiety disorders and breathwork interventions. Only clinical studies using breathwork (without the combination of other interventions) and performed on adult patients diagnosed with an anxiety disorder using the DSM-5 classification system were included. From 1081 articles identified across three databases, sixteen were included for the review. A range of breathwork interventions yielded significant improvements in anxiety symptoms in patients clinically diagnosed with anxiety disorders. The results around the role of hyperventilation in treatment of anxiety were contradictory in few of the examined studies. This evidence-based review supports the clinical utility of breathwork interventions and discusses effective treatment options and protocols that are feasible and accessible to patients suffering anxiety. Current gaps in knowledge for future research directions have also been identified.

Title: Transcutaneous carbon dioxide application accelerates muscle injury repair in rat models

Authors: Akahane S, Sakai Y, Ueha T, Nishimoto H, Inoue M, Niikura T, Kuroda R.

Journal: Int Orthop. 2017 May;41(5):1007-1015. doi: 10.1007/s00264-017-3417-2. Epub 2017 Feb 16. PMID: 28210805.

Link to Pubmed: Transcutaneous carbon dioxide application accelerates muscle injury repair in rat models

Abstract: Purpose: Skeletal muscle injuries are commonly observed in sports and traumatology medicine. Previously, we demonstrated that transcutaneous application of carbon dioxide (CO2) to lower limbs increased the number of muscle mitochondria and promoted muscle endurance. Therefore, we aimed to investigate whether transcutaneous CO2 application could enhance recovery from muscle injury. Methods: Tibialis anterior muscle damage was induced in 27 Sprague Dawley rats via intramuscular injection of bupivacaine. After muscle injury, rats were randomly assigned to transcutaneous CO2-treated or -untreated groups. From each group, three rats were sacrificed at weeks one, two, four and six. At each time point, histology and immunofluorescence analyses were performed, and changes in muscle weight, muscle weight/body weight ratio, muscle fibre circumference, gene expression levels and capillary density were measured. Results: Injured muscle fibres were completely repaired at week six in the CO2-treated group but only partially repaired in the untreated group. The repair of basement and plasma membranes did not differ significantly between groups. However, expression levels of genes and proteins related to muscle protein synthesis were significantly higher in the CO2-treated group and significantly more capillaries four weeks after injury. Conclusion: Transcutaneous CO2 application can accelerate recovery after muscle injury in rats.

Title: Transcutaneous Carbon Dioxide Improves Contractures After Spinal Cord Injury in Rats

Authors: Inoue S, Moriyama H, Yakuwa T, Mizuno E, Suzuki R, Nomura M, Sakai Y, Akisue T.

Journal: Clin Orthop Relat Res. 2019 Aug;477(8):1934-1946. doi: 10.1097/CORR.0000000000000808. PMID: 31135536; PMCID: PMC7000005.

Link to full text: Transcutaneous Carbon Dioxide Improves Contractures After Spinal Cord Injury in Rats

Abstract: Background: Joint contractures are a major complication in patients with spinal cord injuries. Positioning, stretching, and physical therapy are advocated to prevent and treat contractures; however, many patients still develop them. Joint motion (exercise) is crucial to correct contractures. Transcutaneous carbon dioxide (CO2) therapy was developed recently, and its effect is similar to that of exercise. This therapy may be an alternative or complementary approach to exercise. Question/purposes: Using an established model of spinal cord injury in rats with knee flexion contractures, we sought to clarify whether transcutaneous CO2 altered (1) contracture, as measured by ROM; (2) muscular and articular factors contributing to the loss of ROM; (3) fibrosis and fibrosis-related gene expression in muscle; and (4) the morphology of and fibrosis-related protein expression in the joint capsule. Methods: Thirty-six Wistar rats were divided into three equal groups: caged control, those untreated after spinal cord injury, and those treated with CO2 after spinal cord injury. The rats were treated with CO2 from either the first day (prevention) or 15th day (treatment) after spinal cord injury for 2 or 4 weeks. The hindlimbs of rats in the treated group were exposed to CO2 gas for 20 minutes once daily. Knee extension ROM was measured with a goniometer and was measured again after myotomy. We calculated the muscular and articular factors responsible for contractures by subtracting the post-myotomy ROM from that before myotomy. We also quantified histologic muscle fibrosis and evaluated fibrosis-related genes (collagen Type 1, α1 and transforming growth factor beta) in the biceps femoris muscle with real-time polymerase chain reaction. The synovial intima's length was measured, and the distribution of fibrosis-related proteins (Type I collagen and transforming growth factor beta) in the joint capsule was observed with immunohistochemistry. Knee flexion contractures developed in rats after spinal cord injuries at all timepoints. Results: CO2 therapy improved limited-extension ROM in the prevention group at 2 weeks (22° ± 2°) and 4 weeks (29° ± 1°) and in the treatment group at 2 weeks (31° ± 1°) compared with untreated rats after spinal cord injuries (35° ± 2°, mean difference, 13°; 39° ± 1°, mean difference, 9°; and 38° ± 1°, mean difference, 7°, respectively) (95% CI, 10.50-14.86, 8.10-10.19, and 4.73-9.01, respectively; all p < 0.001). Muscular factors decreased in treated rats in the prevention group at 2 weeks (8° ± 2°) and 4 weeks (14°± 1°) and in the treatment group at 2 weeks (14 ± 1°) compared with untreated rats (15° ± 1°, 4.85-9.42; 16° ± 1°, 1.24-3.86; and 17° ± 2°, 1.16-5.34, respectively; all p < 0.05). The therapy improved articular factors in the prevention group at 2 weeks (4° ± 1°) and 4 weeks (6° ± 1°) and in the treatment group at 2 weeks (8° ± 1°) compared with untreated rats (10° ± 1°, 4.05-7.05; 12° ± 1°, 5.18-8.02; and 11° ± 2°, 1.73-5.50, respectively; all p < 0.05). CO2 therapy decreased muscle fibrosis in the prevention group at 2 weeks (p < 0.001). The expression of collagen Type 1, α1 mRNA in the biceps femoris decreased in treated rats in the prevention group at 2 and 4 weeks compared with untreated rat (p = 0.002 and p = 0.008, respectively), although there was little difference in the expression of transforming growth factor beta (p > 0.05). CO2 therapy did not improve shortening of the synovial intima at all timepoints (all p > 0.05). CO2 therapy decreased transforming growth factor beta immunolabeling in joint capsules in the rats in the prevention group at 2 weeks. The staining intensity and Type I collagen pattern showed no differences among all groups at all timepoints. Conclusion: CO2 therapy may be useful for preventing and treating contractures after spinal cord injuries. CO2 therapy particularly appears to be more effective as a prevention and treatment strategy in early-stage contractures before irreversible degeneration occurs, as shown in a rat model.

Title: Increase in carbon dioxide accelerates the performance of endurance exercise in rats

Authors: Ueha T, Oe K, Miwa M, Hasegawa T, Koh A, Nishimoto H, Lee SY, Niikura T, Kurosaka M, Kuroda R, Sakai Y.

Journal: J Physiol Sci. 2018 Jul;68(4):463-470. doi: 10.1007/s12576-017-0548-6. Epub 2017 Jun 10. PMID: 28601950; PMCID: PMC10717130.

Link to full text: Increase in carbon dioxide accelerates the performance of endurance exercise in rats

Abstract: Endurance exercise generates CO2 via aerobic metabolism; however, its role remains unclear. Exogenous CO2 by transcutaneous delivery promotes muscle fibre-type switching to increase endurance power in skeletal muscles. Here we determined the performance of rats running in activity wheels with/without transcutaneous CO2 exposure to clarify its effect on endurance exercise and recovery from muscle fatigue. Rats were randomised to control, training and CO2 groups. Endurance exercise included activity-wheel running with/without transcutaneous CO2 delivery. Running performance was measured after exercise initiation. We also analysed changes in muscle weight and muscle fibres in the tibialis anterior muscle. Running performance improved over the treatment period in the CO2 group, with a concomitant switch in muscle fibres to slow-type. The mitochondrial DNA content and capillary density in the CO2 group increased. CO2 was beneficial for performance and muscle development during endurance exercise: it may enhance recovery from fatigue and support anabolic metabolism in skeletal muscles.

Title: Carbon Dioxide Therapy in the Treatment of Localized Adiposities: Clinical Study and Histopathological Correlations

Authors: Brandi C, D'Aniello C, Grimaldi L, Bosi B, Dei I, Lattarulo P, Alessandrini C.

Journal: Aesthetic Plast Surg. 2001 May-Jun;25(3):170-4. doi: 10.1007/s002660010116. PMID: 11426306.

Link to full text: Carbon Dioxide Therapy in the Treatment of Localized Adiposities: Clinical Study and Histopathological Correlations

Abstract: The authors report their experience using carbon dioxide (CO2) therapy for the treatment of 48 female patients presenting adipose accumulations, located on the thighs, knees, and/or abdomen; a Carbomed Programmable Automatic Carbon Dioxide Therapy apparatus was used. In light of the effects of CO2 on the microcirculation recently described in the literature, we expected this gas, which we administered subcutaneously, to positively affect the physiological oxidative lipolytic process. The aim of our study was to evaluate the effect of this therapy on localized adiposities. As such, we describe the method we used and report the results observed in the areas treated (in terms of reduction in maximum circumference) as well as side effects. Furthermore, we assessed the effect of subcutaneous administration of CO2 on the microcirculation by showing changes in the Laser Doppler signal and in the concentration of transcutaneous oxygen tension (tcPO2). Pre- and posttreatment biopsies of tissues were performed in seven patients in order to study the changes induced by the use of CO2 on both adipose and connective tissues. All data obtained were statistically analyzed; values of P < 0.05 were considered significant.

Title: Increased net water loss by oral compared to nasal expiration in healthy subjects

Authors: Svensson S, Olin AC, Hellgren J.

Journal: Rhinology. 2006 Mar;44(1):74-7. PMID: 16550955.

Link to Pubmed: Increased net water loss by oral compared to nasal expiration in healthy subjects

Abstract: Aim of the study: To compare the difference in respiratory water loss during expiration through the nose and through the mouth, in healthy subjects. Methods: The study included 19 healthy, non-smoking volunteers without any present history of non-infectious rhinitis, presenting with symptoms of rhinitis, asthma or previous nasal surgery. Nasal and oral expiratory breath condensates were collected using a breath condenser during tidal respiration at indoor resting conditions. During the nasal breath condensate sampling, the subjects were breathing into a transparent face mask covering the nose and the mouth with the mouth closed. During the oral breath condensate sampling, the subjects inhaled through the nose and exhaled through a mouthpiece connected to the condenser. The airflow during the sampling was assessed with a dry-spirometer connected to the condenser. Sampling was stopped after 100 litres of expired air for each breathing mode. Nasal sampling was done before and after decongestion of the nasal mucosa with oxymetazoline, 0.5 mg/ml. The effect on the nasal mucosa was assessed with acoustic rhinometry. Results: The mean loss of expired water was 42% less by nasal expiration before decongestion than by oral expiration (1.9 x 10(-3) g/L min compared to 2.7 x 10(-3) g/L min, p < 0.001). The mean expiratory minute ventilation was 9.0 L/min by nasal respiration and 9.8 L/min by oral respiration. Decongestion of the nasal mucosa showed a mean increase of the cross-sectional area at 4 cm from the nostril (1.44 to 1.67 cm2, p = 0.0024), but there was no effect on the net water loss (1.9 x 10(-3) g/Lmin vs 1.9 x 10(-3) g/Lmin). Conclusion: This study showed that the net water loss increased by 42% when the breathing mode was switched from nasal to oral expiration during tidal breathing in healthy subjects. Increased water and energy loss by oral breathing could be a contributing factor to the symptoms seen in patients suffering from nasal obstruction.

Title: Levels of end-tidal carbon dioxide are low despite normal respiratory rate in individuals with long COVID

Authors: Wood J, Tabacof L, Tosto-Mancuso J, McCarthy D, Kontorovich A, Putrino D.

Journal: J Breath Res. 2021 Dec 8;16(1). doi: 10.1088/1752-7163/ac3c18. PMID: 34808607.

Link to Pubmed: Levels of end-tidal carbon dioxide are low despite normal respiratory rate in individuals with long COVID

Abstract: ETCO2 and respiratory rate (RR) were measured in patients attending an outpatient clinic using an EMMA capnograph (Masimo Corporation, Irvine, CA). Approval for the collection and publication of this data was provided by the relevant Institutional Review Board (STUDY-20-001537). All patients were previously reviewed by a physician and diagnosed with confirmed (via PCR and/or antibody test) or probable (according to World Health Organization and Center for Disease Control and Prevention guidelines [6, 7]) past COVID-19 infection. The criteria for diagnosis of long COVID was the presence of persistent symptoms for at least 12 weeks after initial infection [2]. The capnograph was calibrated and a healthy control was used to check device readings at the commencement of each clinic. At the time of assessment, patients were seated and at rest, and had not performed other assessments or procedures immediately prior. Patients were instructed to breathe orally through the capnograph adapter at their resting rate and depth for a minimum of 15 s, and until the ETCO2 level was stable for a further period of at least 5 s. Data were analyzed using Stata (StataCorp LLC, TX), with descriptive statistics and Pearson correlation coefficient provided.

Title: Role of the medullary raphe nuclei in the respiratory response to CO2

Authors: Dreshaj IA, Haxhiu MA, Martin RJ.

Journal: Respir Physiol. 1998 Jan;111(1):15-23. doi: 10.1016/s0034-5687(97)00110-2. PMID: 9496468.

Link to Pubmed: Role of the medullary raphe nuclei in the respiratory response to CO2

Abstract: We characterized the role of neurons within the midline of the medulla oblongata on phrenic and hypoglossal nerve responses to hypercapnia during early-development. Studies were performed on decorticate or anesthetized; vagotomized and mechanically ventilated 14-20 day old piglets. Reversible withdrawal of midline neuronal activity was induced by microinjections of lidocaine (2%, 300 nl; n = 10) and lesioning was caused by microinjections of the neurotoxic agent, ibotenic acid (n = 12), at the same sites. At any given end-tidal CO2, peak phrenic and hypoglossal activities after lidocaine were significantly lower than in the control period (P < 0.01). Similarly, 1-2 h after injections of ibotenic acid, both phrenic and hypoglossal nerve responses to CO2 were significantly lower than in the control period (P < 0.01). The results indicate for the first time that the medullary midline neurons are required for full expression of ventilatory responses to hypercapnia and raise the possibility that dysfunction of these nuclei may contribute to respiratory instability during early postnatal life.

Title: Smaller amygdala is associated with anxiety in patients with panic disorder

Authors: Hayano F, Nakamura M, Asami T, Uehara K, Yoshida T, Roppongi T, Otsuka T, Inoue T, Hirayasu Y.

Journal: Psychiatry Clin Neurosci. 2009 Jun;63(3):266-76. doi: 10.1111/j.1440-1819.2009.01960.x. PMID: 19566756.

Link to full text: Smaller amygdala is associated with anxiety in patients with panic disorder

Abstract: Aims: Anxiety a core feature of panic disorder, is linked to function of the amygdala. Volume alterations in the brain of patients with panic disorder have previously been reported, but there has been no report of amygdala volume association with anxiety. Methods: Volumes of hippocampus and amygdala were manually measured using magnetic resonance imaging obtained from 27 patients with panic disorder and 30 healthy comparison subjects. In addition the amygdala was focused on, applying small volume correction to optimized voxel-based morphometry (VBM). State-Trait Anxiety Inventory and the NEO Personality Inventory Revised were also used to evaluate anxiety. Results: Amygdala volumes in both hemispheres were significantly smaller in patients with panic disorder compared with control subjects (left: t = -2.248, d.f. = 55, P = 0.029; right: t = -2.892, d.f. = 55, P = 0.005). VBM showed that structural alteration in the panic disorder group occurred on the corticomedial nuclear group within the right amygdala (coordinates [x,y,z (mm)]: [26,-6,-16], Z score = 3.92, family-wise error-corrected P = 0.002). The state anxiety was negatively correlated with the left amygdala volume in patients with panic disorder (r = -0.545, P = 0.016). Conclusions: These findings suggested that the smaller volume of the amygdala may be associated with anxiety in panic disorder. Of note, the smaller subregion in the amygdala estimated on VBM could correspond to the corticomedial nuclear group including the central nucleus, which may play a crucial role in panic attack.

Title: Induction of c-Fos in 'panic/defence'-related brain circuits following brief hypercarbic gas exposure

Authors: Johnson PL, Fitz SD, Hollis JH, Moratalla R, Lightman SL, Shekhar A, Lowry CA.

Journal: J Psychopharmacol. 2011 Jan;25(1):26-36. doi: 10.1177/0269881109353464. Epub 2010 Jan 15. PMID: 20080924.

Link to Pubmed: Induction of c-Fos in 'panic/defence'-related brain circuits following brief hypercarbic gas exposure

Abstract: Inspiration of air containing high concentrations of carbon dioxide (CO(2); hypercarbic gas exposure) mobilizes respiratory, sympathetic and hypothalamic-pituitary-adrenal axis responses and increases anxiety-like behaviour in rats and humans. Meanwhile the same stimulus induces panic attacks in the majority of panic disorder patients. However, little is known about the neural circuits that regulate these acute effects. In order to determine the effects of acute hypercarbic gas exposure on forebrain and brainstem circuits, conscious adult male rats were placed in flow cages and exposed to either atmospheric air or increasing environmental CO(2) concentrations (from baseline concentrations up to 20% CO(2)) during a 5 min period. The presence of immunoreactivity for the protein product of the immediate-early gene c-fos was used as a measure of functional cellular responses. Exposing rats to hypercarbic gas increased anxiety-related behaviour and increased numbers of c-Fos-immunoreactive cells in subcortical regions of the brain involved in: (1) the initiation of fear- or anxiety-associated behavioural responses (i.e. the dorsomedial hypothalamus, perifornical nucleus and dorsolateral and ventrolateral periaqueductal gray); (2) mobilization of the hypothalamic-pituitary-adrenal axis (i.e. the dorsomedial hypothalamus, perifornical nucleus and paraventricular hypothalamic nucleus); and (3) initiation of stress-related sympathetic responses (i.e. the dorsomedial hypothalamus, dorsolateral periaqueductal grey and rostroventrolateral medulla). These findings have implications for understanding how the brain senses changes in environmental CO(2) concentrations and the neural mechanisms underlying the subsequent adaptive changes in stress-related physiology and behaviour.

Title: Amygdalar atrophy in panic disorder patients detected by volumetric magnetic resonance imaging

Authors: Massana G, Serra-Grabulosa JM, Salgado-Pineda P, Gastó C, Junqué C, Massana J, Mercader JM, Gómez B, Tobeña A, Salamero M.

Journal: Neuroimage. 2003 May;19(1):80-90. doi: 10.1016/s1053-8119(03)00036-3. PMID: 12781728.

Link to Pubmed: Amygdalar atrophy in panic disorder patients detected by volumetric magnetic resonance imaging

Abstract: It has been suggested that the pathophysiology of panic disorder (PD) may involve abnormalities in several brain structures, including the amygdala. To date, however, no study has used quantitative structural neuroimaging techniques to examine amygdalar anatomy in this disorder. Volumetric magnetic resonance imaging (MRI) studies of the amygdalas, hippocampi, and temporal lobes were conducted in 12 drug-free, symptomatic PD patients (six females and six males), and 12 case-matched healthy comparison subjects. Volumetric MRI data were normalized for brain size. PD patients were found to have smaller left-sided and right-sided amygdalar volumes than controls. No differences were found in either hippocampi or temporal lobes. These findings provide new evidence of changes in amygdalar structure in PD and warrant further anatomical and MRI brain studies of patients with this disorder.

Title: Effects of decortication and carotid sinus nerve section on ventilation of the rat

Authors: Maskrey M, Megirian D, Nicol SC.

Journal: Respir Physiol. 1981 Mar;43(3):263-73. doi: 10.1016/0034-5687(81)90108-0. PMID: 6792671.

Link to Pubmed: Effects of decortication and carotid sinus nerve section on ventilation of the rat

Abstract: The effect on ventilation of exposure to hypoxic, hypercapnic and hypoxic/hypercapnic gas mixtures was studied before and after functional decortication of intact rats and rats in which the carotid chemoreceptors had been disconnected. Unanaesthetized rats responded to both hypoxia and hypercapnia with an increase in minute ventilation (V) through increases in both frequency (f) and tidal volume (VT). Decortication led to a greater V response to CO2. This was through an effect on f, rather than VT. Carotid sinus nerve section (CSNS) caused a lessening in the V response to gas mixtures, f and VT being equally affected. Decortication, following CSNS, increased the V response but this time through increased VT rather than f. This effect on VT was not specific to any particular gas mixture. It is concluded that the carotid body chemoreceptors, together with the bulbopontine rate controller, influence the response to CO2. It is further suggested that this integration takes place in the reticular formation and is normally under some degree of inhibition from the cerebral cortex.

Title: Neural Correlates of Competing Fear Behaviors Evoked by an Innately Aversive Stimulus

Authors: Mongeau R, Miller GA, Chiang E, Anderson DJ.

Journal: J Neurosci. 2003 May 1;23(9):3855-68. doi: 10.1523/JNEUROSCI.23-09-03855.2003. PMID: 12736356; PMCID: PMC6742203.

Link to full text: Neural Correlates of Competing Fear Behaviors Evoked by an Innately Aversive Stimulus

Abstract: Environment and experience influence defensive behaviors, but the neural circuits mediating such effects are not well understood. We describe a new experimental model in which either flight or freezing reactions can be elicited from mice by innately aversive ultrasound. Flight and freezing are negatively correlated, suggesting a competition between fear motor systems. An unfamiliar environment or a previous aversive event, moreover, can alter the balance between these behaviors. To identify potential circuits controlling this competition, global activity patterns in the whole brain were surveyed in an unbiased manner by c-fos in situ hybridization, using novel experimental and analytical methods. Mice predominantly displaying freezing behavior had preferential neural activity in the lateral septum ventral and several medial and periventricular hypothalamic nuclei, whereas mice predominantly displaying flight had more activity in cortical, amygdalar, and striatal motor areas, the dorsolateral posterior zone of the hypothalamus, and the vertical limb of the diagonal band. These complementary patterns of c-fos induction, taken together with known connections between these structures, suggest ways in which the brain may mediate the balance between these opponent defensive behaviors.

Title: CO2, brainstem chemoreceptors and breathing

Authors: Nattie E.

Journal: Prog Neurobiol. 1999 Nov;59(4):299-331. doi: 10.1016/s0301-0082(99)00008-8. PMID: 10501632.

Link to full text: CO2, brainstem chemoreceptors and breathing

Abstract: The regulation of breathing relies upon chemical feedback concerning the levels of CO2 and O2. The carotid bodies, which detect O2, provide tonic excitation to brainstem respiratory neurons under normal conditions and dramatic excitation if O2 levels fall. Feedback for CO2 involves the carotid body and receptors in the brainstem, central chemoreceptors. Small increases in CO2 produce large increases in breathing. Decreases in CO2 below normal can, in sleep and anesthesia, decrease breathing, even to apnea. Central chemoreceptors, once thought localized to the surface of the ventral medulla, are likely distributed more widely with sites presently identified in the: (1) ventrolateral medulla; (2) nucleus of the solitary tract; (3) ventral respiratory group; (4) locus ceruleus; (5) caudal medullary raphé; and (6) fastigial nucleus of the cerebellum. Why so many chemoreceptor sites? Hypotheses, some with supporting data, include the following. Geographical specificity; all regions of the brainstem with respiratory neurons contain chemoreceptors. Stimulus intensity; some sites operate in the physiological range of CO2 values, others only with more extreme changes. Stimulus specificity; CO2 or pH may be sensed by multiple mechanisms. Temporal specificity; some sites respond more quickly to changes on blood or brain CO2 or pH. Syncytium; chemosensitive neurons may be connected via low resistance, gap junctions. Arousal state: sites may vary in effectiveness and importance dependent on state of arousal. Overall, as judged by experiments of nature, and in the laboratory, central chemoreceptors are critical for adequate breathing in sleep, but other aspects of the control system can maintain breathing in wakefulness.

Title: Panic and the Brainstem: Clues from Neuroimaging Studies

Authors: Perna G, Guerriero G, Brambilla P, Caldirola D.

Journal: CNS Neurol Disord Drug Targets. 2014;13(6):1049-56. doi: 10.2174/1871527313666140612112923. PMID: 24923341.

Link to Pubmed: Panic and the Brainstem: Clues from Neuroimaging Studies

Abstract: One of the most influential theories has conceived unexpected panic attack (PA) as a primal defensive reaction to threat within the internal milieu of the body. This theory is based on findings suggesting the involvement of dysfunctional respiratory regulation and/or abnormally sensitive central neural network of carbon dioxide (CO2)/hydrogen ion (H+) chemoreception in PA. Thus, unexpected PA may be related to phylogenetically older brain structures, including the brainstem areas, which process basic functions related to the organism's internal milieu. The brainstem represents a crucial area for homeostatic regulation, including chemoreception and cardio-respiratory control. In addition, the midbrain dorsal periaqueductal gray may be involved in the unconditioned defense reactions to proximal threats, including internal physical stimuli. Our aim was to specifically consider the potential involvement of the brainstem in panic disorder (PD) by a comprehensive review of the available neuroimaging studies. Available data are limited and potentially affected by several limitations. However, preliminary evidence of a role of the brainstem in PD can be found and, secondly, the brainstem serotonergic system seems to be involved in panic modulation with indications of both altered serotonergic receptors and 5-HT transporter bindings. In conclusion, our review suggests that the brainstem may be involved in psychopathology of PD and supports the relevant role of subcortical serotonergic system in panic pathogenesis.

Title: fMRI of fearful facial affect recognition in panic disorder: the cingulate gyrus-amygdala connection

Authors: Pillay SS, Gruber SA, Rogowska J, Simpson N, Yurgelun-Todd DA.

Journal: J Affect Disord. 2006 Aug;94(1-3):173-81. doi: 10.1016/j.jad.2006.04.007. Epub 2006 Jun 16. PMID: 16782207.

Link to Pubmed: fMRI of fearful facial affect recognition in panic disorder: the cingulate gyrus-amygdala connection

Abstract: Background: This study investigated cingulate cortex (CC) and amygdala response to fearful facial affect recognition in patients with panic disorder (PD) as measured by BOLD fMRI during the presentation of static facial images. Methods: Eight patients with PD and eight controls were studied. Scanning was performed on a GE Signa 1.5-T scanner. Echo planar and high-resolution MR images were acquired. Results: Controls produced greater CC activation compared to patients with PD in response to fearful faces. Furthermore, patients with PD produced less amygdala activation than controls in response to fearful faces. During the neutral face condition, overall activation for the CC was significantly greater in PD patients although anterior cingulate cortex (ACC) activation was not as markedly different between both groups. There were no between group differences in amygdala activation on exposure to the neutral face. Only left CC activation was significantly correlated negatively with HAM-A in PD patients in the fearful facial affect condition. Limitations: Although comparable to similar studies, the sample size is small enough to warrant further investigation. Also, the effects of medication need to be considered when interpreting these results. Conclusions: Patients with PD activate the ACC and amygdala significantly less than controls when asked to identify fearful facial affect during fMRI. The higher the anxiety, the lower the left CC activation. Thus, chronic hyperarousal in PD may diminish attentional resources and emotional response reflected in reduced ACC and amygdala activation. Even if these are medication effects, the differences from controls are clinically relevant.

Title: Neuroanatomical Correlates of a Lactate-Induced Anxiety Attack

Authors: Reiman EM, Raichle ME, Robins E, Mintun MA, Fusselman MJ, Fox PT, Price JL, Hackman KA.

Journal: Arch Gen Psychiatry. 1989 Jun;46(6):493-500. doi: 10.1001/archpsyc.1989.01810060013003. PMID: 2786401.

Link to Pubmed: Neuroanatomical Correlates of a Lactate-Induced Anxiety Attack

Abstract: Positron emission tomographic measurements of regional blood flow were used to assess local neuronal activity in patients with panic disorder and in normal control subjects before and during the infusion of sodium lactate. A new technique for the analysis of positron emission tomographic data was employed to identify significant changes in regional blood flow associated with lactate infusion in the panicking patients, nonpanicking patients, and controls. Lactate-induced panic was associated with significant blood flow increases bilaterally in the temporal poles; bilaterally in insular cortex, claustrum, or lateral putamen; bilaterally in or near the superior colliculus; and in or near the left anterior cerebellar vermis. Lactate infusion was not associated with significant changes in regional blood flow in the nonpanicking patients or control subjects. Thus, the identified regions seemed to be involved in an anxiety attack.

Title: Ventilatory response of decorticate and decerebrate cats to hypoxia and CO2

Authors: Tenney SM, Ou LC.

Journal: Respir Physiol. 1977 Feb;29(1):81-92. doi: 10.1016/0034-5687(77)90119-0. PMID: 847311.

Link to Pubmed: Ventilatory response of decorticate and decerebrate cats to hypoxia and CO2

Abstract: The steady state ventilatory response of normal, fully awake cats was studied under graded hypoxia (at PAO2 = 110, 55, 45 torr) with PACO2 controlled throughout at the resting, normoxic level and at +5 torr. Subsequently, either a mid-collicular decerebration or a decortication was performed, and the ventilatory studies were repeated. Respiratory frequency, tidal volume, and ventilation in the decerebrate state responded to hypoxia and hypercapnia in a manner indistinguishable from the control. The decorticate cats, however, exhibited an exaggerated response to hypoxia, principally the result of increased frequency. The negative hypoxic, hypercapnic interaction, characteristic of awake cats, was demonstrable in both the decerebrate and decorticate animals. The findings are interpreted as revealing coupled descending influences on the medullary respiratory centers in hypoxia--one that is facilitatory and originates in the diencephalon, and the other, inhibitory, from the cerebrum. The significance of this suprapontine system in normal hypoxic ventilatory control is discussed.

Title: Amygdala circuitry mediating reversible and bidirectional control of anxiety

Authors: Tye KM, Prakash R, Kim SY, Fenno LE, Grosenick L, Zarabi H, Thompson KR, Gradinaru V, Ramakrishnan C, Deisseroth K.

Journal: Nature. 2011 Mar 17;471(7338):358-62. doi: 10.1038/nature09820. Epub 2011 Mar 9. PMID: 21389985; PMCID: PMC3154022.

Link to full text: Amygdala circuitry mediating reversible and bidirectional control of anxiety

Abstract: Anxiety--a sustained state of heightened apprehension in the absence of immediate threat--becomes severely debilitating in disease states. Anxiety disorders represent the most common of psychiatric diseases (28% lifetime prevalence) and contribute to the aetiology of major depression and substance abuse. Although it has been proposed that the amygdala, a brain region important for emotional processing, has a role in anxiety, the neural mechanisms that control anxiety remain unclear. Here we explore the neural circuits underlying anxiety-related behaviours by using optogenetics with two-photon microscopy, anxiety assays in freely moving mice, and electrophysiology. With the capability of optogenetics to control not only cell types but also specific connections between cells, we observed that temporally precise optogenetic stimulation of basolateral amygdala (BLA) terminals in the central nucleus of the amygdala (CeA)--achieved by viral transduction of the BLA with a codon-optimized channelrhodopsin followed by restricted illumination in the downstream CeA--exerted an acute, reversible anxiolytic effect. Conversely, selective optogenetic inhibition of the same projection with a third-generation halorhodopsin (eNpHR3.0) increased anxiety-related behaviours. Importantly, these effects were not observed with direct optogenetic control of BLA somata, possibly owing to recruitment of antagonistic downstream structures. Together, these results implicate specific BLA-CeA projections as critical circuit elements for acute anxiety control in the mammalian brain, and demonstrate the importance of optogenetically targeting defined projections, beyond simply targeting cell types, in the study of circuit function relevant to neuropsychiatric disease.

Title: Neurobiology of panic and pH chemosensation in the brain

Authors: Wemmie JA.

Journal: Dialogues Clin Neurosci. 2011;13(4):475-83. doi: 10.31887/DCNS.2011.13.4/jwemmie. PMID: 22275852; PMCID: PMC3263394.

Link to full text: Neurobiology of panic and pH chemosensation in the brain

Abstract: Panic disorder is a common and disabling illness for which treatments are too frequently ineffective. Greater knowledge of the underlying biology could aid the discovery of better therapies. Although panic attacks occur unpredictably, the ability to provoke them in the laboratory with challenge protocols provides an opportunity for crucial insight into the neurobiology of panic. Two of the most well-studied panic provocation challenges are CO(2) inhalation and lactate infusion. Although it remains unclear how these challenges provoke panic animal models of CO(2) and lactate action are beginning to emerge, and offer unprecedented opportunities to probe the molecules and circuits underlying panic attacks. Both CO(2) and lactate alter pH balance and may generate acidosis that can influence neuron function through a growing list of pH-sensitive receptors. These observations suggest that a key to better understanding of panic disorder may He in more knowledge of brain pH regulation and pH-sensitive receptors. Keywords: CO2; chemo-sensation; lactate, brain pH; panic disorder; provocation challenge.

Title: Ventilatory response of decorticate and decerebrate cats to hypoxia and CO2

Authors: Bailey JE, Argyropoulos SV, Kendrick AH, Nutt DJ.

Journal: Depress Anxiety. 2005;21(1):18-25. doi: 10.1002/da.20048. PMID: 15782425.

Link to Pubmed: Ventilatory response of decorticate and decerebrate cats to hypoxia and CO2

Abstract: The study of carbon dioxide (CO2) inhalation in psychiatry has a long and varied history, with recent interest in using inhaled CO2 as an experimental tool to explore the neurobiology and treatment of panic disorder. As a consequence, many studies have examined the panic-like response to the gas either using the single or double breath 35% CO2 inhalation or 5-7% CO2 inhaled for 15-20 min, or rebreathing 5% CO2 for a shorter time. However, this lower dose regime produces little physiological or psychological effects in normal volunteers. For this reason we have studied the effects of a higher concentration of CO2, 7.5%, given over 20 min. Twenty healthy volunteers were recruited to a double blind, placebo-controlled study where air and 7.5% CO2 were inhaled for 20 min. Cardiovascular measures and subjective ratings were obtained. When compared to air, inhaling 7.5% CO2 for 20 min increases systolic blood pressure and heart rate, indicating increased autonomic arousal. It also increases ratings of anxiety and fear and other subjective symptoms associated with an anxiety state. The inhalation of 7.5% CO2 for 20 min is safe for use in healthy volunteers and produces robust subjective and objective effects. It seems promising as an anxiety provocation test that could be beneficial in the study of the effects of anxiety on sustained performance, the discovery of novel anxiolytic agents, and the study of brain circuits and mechanisms of anxiety.

Title: The 35% CO2 challenge in panic disorder: optimization by receiver operating characteristic (ROC) analysis

Authors: Battaglia M, Perna G.

Journal: J Psychiatr Res. 1995 Mar-Apr;29(2):111-9. doi: 10.1016/0022-3956(94)00045-s. PMID: 7666379.

Link to Pubmed: The 35% CO2 challenge in panic disorder: optimization by receiver operating characteristic (ROC) analysis

Abstract: To test the power of the 35% CO2 test as a challenge for panic disorder (PD), and to set an ideal threshold of discrimination between patients and controls, we analysed by receiver operating characteristic (ROC) analysis the responses of 91 out-patients with PD and 46 controls who inhaled a 35% CO2/65% O2 gas mixture. ROC analysis confirmed that the CO2 challenge discriminates well between PD patients and controls, with 86% probability to classify them correctly on the basis of subjective anxiety after the test. A relatively modest increment in subjective anxiety (i.e. an absolute increment of 20 units, or a relative increment of 26% of subjective anxiety) proved to be the ideal threshold to separate the two groups of our sample.

Title: On the psychotropic effects of carbon dioxide

Authors: Colasanti A, Esquivel G, Schruers KJ, Griez EJ.

Journal: Curr Pharm Des. 2012;18(35):5627-37. doi: 10.2174/138161212803530745. PMID: 22632467.

Link to Pubmed: On the psychotropic effects of carbon dioxide

Abstract: It has been well established that the inhalation of Carbon Dioxide (CO2) can induce in humans an emotion closely replicating spontaneous panic attacks, as defined by current psychiatry nosology. The purpose of this review is to provide a critical summary of the data regarding CO2's psychopharmacological properties and underlying mechanisms. The authors review the literature on the human and animal response for the exposure of exogenous CO2 focusing on five points of interest: 1) the early history of the use of CO2 as an anesthetic and therapeutic agent, 2) the subjective effects of breathing CO2 at different concentrations in humans, 3) the use of CO2 in experimental psychiatric research as an experimental model of panic, 4) the pharmacological modulation of CO2-induced responses, and 5) the putative neurobiological mechanisms underlying the affective state induced by CO2. The authors conclude with an evolutionary-inspired notion that CO2 might act as an agent of a primal emotion serving a homeostatic function, in the control of respiration and acid-base balance.

Title: Body fluids after CO2 inhalation: insight into panic mechanisms?

Authors: Griez E, van den Hout MA, Verstappen F.

Journal: Eur Arch Psychiatry Neurol Sci. 1987;236(6):369-71. doi: 10.1007/BF00377427. PMID: 3119345.

Link to Pubmed: Body fluids after CO2 inhalation: insight into panic mechanisms?

Abstract: Blood gases and electrolyte fluctuations were studied in arterial blood, after a single 35% CO2-65% O2 inhalation, which is known to trigger panic attacks in patients with panic disorder. The immediate effect of this maneuver was a brief hypercapnic acidosis followed by a slight alkalotic rebound, with shifts in Ca2+ and K+. The possible effect of these changes on neuronal membrane excitability is discussed, referring to recent experimental findings in panic provocation.

Title: A Long-Term Prospective Evaluation of First-Degree Relatives of Panic Patients Who Underwent the 35% CO2 Challenge

Authors: Perna G, Cocchi S, Allevi L, Bussi R, Bellodi L.

Journal: Biol Psychiatry. 1999 Feb 1;45(3):365-7. doi: 10.1016/s0006-3223(98)00030-4. PMID: 10023515.

Link to Pubmed: A Long-Term Prospective Evaluation of First-Degree Relatives of Panic Patients Who Underwent the 35% CO2 Challenge

Abstract: Background: This follow-up study investigated the potential priming effect of the 35% CO2 challenge on the development of anxiety disorders and/or panic attacks in healthy first-degree relatives of panic patients across a period of 3-4 years subsequent to the challenge. Methods: Thirty-one relatives who underwent the 35% CO2 challenge 3-4 years before and 14 relatives, free from psychiatric diagnoses in the same period, were directly reevaluated for the presence of anxiety disorders and panic attacks. Results: None developed anxiety disorders and only 1, among relatives previously tested with the 35% CO2 challenge, reported sporadic panic attacks. Conclusions: The 35% CO2 challenge is a safe research paradigm in the investigation of healthy subjects with a familial vulnerability to panic, and CO2 hypersensitivity might be considered a trait marker of an underlying familial vulnerability to panic disorder.

Title: Examining the latent class structure of CO2 hypersensitivity using time course trajectories of panic response systems

Authors: Roberson-Nay R, Beadel JR, Gorlin EI, Latendresse SJ, Teachman BA.

Journal: J Behav Ther Exp Psychiatry. 2015 Jun;47:68-76. doi: 10.1016/j.jbtep.2014.10.013. Epub 2014 Nov 15. PMID: 25496936; PMCID: PMC4324118.

Link to full text: Examining the latent class structure of CO2 hypersensitivity using time course trajectories of panic response systems

Abstract: Background and objectives: Carbon dioxide (CO2) hypersensitivity is hypothesized to be a robust endophenotypic marker of panic spectrum vulnerability. The goal of the current study was to explore the latent class trajectories of three primary response systems theoretically associated with CO2 hypersensitivity: subjective anxiety, panic symptoms, and respiratory rate (fR). Methods: Participants (n = 376; 56% female) underwent a maintained 7.5% CO2 breathing task that included three phases: baseline, CO2 air breathing, and recovery. Growth mixture modeling was used to compare response classes (1…n) to identify the best-fit model for each marker. Panic correlates also were examined to determine class differences in panic vulnerability. Results: For subjective anxiety ratings, a three-class model was selected, with individuals in one class reporting an acute increase in anxiety during 7.5% CO2 breathing and a return to pre-CO2 levels during recovery. A second, smaller latent class was distinguished by elevated anxiety across all three phases. The third class reported low anxiety reported during room air, a mild increase in anxiety during 7.5% CO2 breathing, and a return to baseline during recovery. Latent class trajectories for fR yielded one class whereas panic symptom response yielded two classes. Limitations: This study examined CO2 hypersensitivity in one of the largest samples to date, but did not ascertain a general population sample thereby limiting generalizability. Moreover, a true resting baseline measure of fR was not measured. Conclusions: Two classes potentially representing different risk pathways were observed. Implications of results will be discussed in the context of panic risk research. Keywords: Anxiety; Carbon dioxide hypersensitivity; Latent class; Panic; Respiratory; Risk.

Title: Five percent carbon dioxide challenge: valid analogue and marker of panic disorder?

Authors: Sanderson WC, Wetzler S.

Journal: Biol Psychiatry. 1990 Apr 1;27(7):689-701. doi: 10.1016/0006-3223(90)90584-o. PMID: 2109638.

Link to Pubmed: Five percent carbon dioxide challenge: valid analogue and marker of panic disorder?

Abstract: The administration of 5% carbon dioxide (CO2) to patients with panic disorder (PD) induces a behavioral response similar to a naturally occurring panic attack. This article reviews the literature on the nature and incidence of this response. We conclude that the 5% CO2 challenge test is a valid and useful laboratory analogue of naturally occurring panic attacks, and shows promise as a marker to identify a subset of PD patients. Though further research on reliability, validity, and dose-response effects must be conducted, the CO2 challenge test provides important information regarding the phenomenology of panic states.

Title: Transcutaneous carbon dioxide application suppresses bone destruction caused by breast cancer metastasis

Authors: Takemori T, Kawamoto T, Ueha T, Toda M, Morishita M, Kamata E, Fukase N, Hara H, Fujiwara S, Niikura T, Kuroda R, Akisue T.

Journal: Oncology Reports, 40, 2079-2087. https://doi.org/10.3892/or.2018.6608

Link to full text: Transcutaneous carbon dioxide application suppresses bone destruction caused by breast cancer metastasis

Abstract: Hypoxia plays a significant role in cancer progression, including metastatic bone tumors. We previously reported that transcutaneous carbon dioxide (CO2) application could decrease tumor progression through the improvement of intratumor hypoxia. Therefore, we hypothesized that decreased hypoxia using transcutaneous CO2 could suppress progressive bone destruction in cancer metastasis. In the present study, we examined the effects of transcutaneous CO2 application on metastatic bone destruction using an animal model. The human breast cancer cell line MDA-MB-231 was cultured in vitro under three different oxygen conditions, and the effect of altered oxygen conditions on the expression of osteoclast-differentiation and osteolytic factors was assessed. An in vivo bone metastatic model of human breast cancer was created by intramedullary implantation of MDA-MB-231 cells into the tibia of nude mice, and treatment with 100% CO2 or a control was performed twice weekly for two weeks. Bone volume of the treated tibia was evaluated by micro-computed tomography (µCT), and following treatment, histological evaluation was performed by hematoxylin and eosin staining and immunohistochemical staining for hypoxia-inducible factor (HIF)-1α, osteoclast-differentiation and osteolytic factors, and tartrate-resistant acid phosphatase (TRAP) staining for osteoclast activity. In vitro experiments revealed that the mRNA expression of RANKL, PTHrP and IL-8 was significantly increased under hypoxic conditions and was subsequently reduced by reoxygenation. In vivo results by µCT revealed that bone destruction was suppressed by transcutaneous CO2, and that the expression of osteoclast-differentiation and osteolytic factors, as well as HIF-1α, was decreased in CO2-treated tumor tissues. In addition, multinucleated TRAP-positive osteoclasts were significantly decreased in CO2-treated tumor tissues. Hypoxic conditions promoted bone destruction in breast cancer metastasis, and reversal of hypoxia by transcutaneous CO2 application significantly inhibited metastatic bone destruction along with decreased osteoclast activity. The findings in this study strongly indicated that transcutaneous CO2 application could be a novel therapeutic strategy for treating metastatic bone destruction.

Title: Effects of an artificially carbonated bath on athletic warm-up

Authors: Akamine T, Taguchi N.

Journal: J Hum Ergol (Tokyo). 1998 Dec;27(1-2):22-9. PMID: 11579696.

Link to full text: Effects of an artificially carbonated bath on athletic warm-up

Abstract: The effects of an artificially carbonated bath (36 degrees C, CO2 300 ppm, 20 minutes) on the warm-up of swimmers was compared with those of a freshwater bath (36 degrees C, 20 minutes). Carbon dioxide is reported to have a vasodilatory effect on peripheral blood vessels of cutaneous and muscular tissue and to promote blood flow. We observed that the warm-up effects of a carbonated bath before swimming on the hematocrit, white blood cell, total plasma protein, and total cholesterol levels in venous blood were significantly increased more than those of a freshwater bath before swimming in recovery period (p < 0.05). Thus the carbonated bath tended to be more effective for increasing the concentrations of blood components. In the recovery period, the carbonated bath before swimming also resulted in significantly smaller changes in blood lactic acid and heart rate than those of a freshwater bath before swimming (p < 0.05). The decrease in electromyography of the M. rectus femoris during swimming suggested more efficient muscle activity after a carbonated bath. Therefore after a carbonated bath, swimmers should have a higher reserve left in the cardiovascular system, resulting in better performance during swimming and less accumulation of fatigue-related metabolites after swimming.

Title: Enhanced Athletic Recovery Using Cold-Water Immersion with Dissolved CO2 and H2

Authors: Yoshimura M, Fukuoka Y, Sawada Y, Ichikawa H, Nakamura M.

Journal: International Journal of Physical Medicine & Rehabilitation

Link to full text: Enhanced Athletic Recovery Using Cold-Water Immersion with Dissolved CO2 and H2

Abstract: A Cold therapy is widely recognized as a prescription for acute-phase recovery in athletes. However, it has been suggested that vasoconstriction caused by cooling may, in fact, delay the recovery process after exercise. Therefore, we are researching a new cooling method that involves supplementing ice baths with carbon dioxide gas, which has vasodilatory effects, and hydrogen gas, which has anti-inflammatory properties. This new approach aims to improve muscle blood flow and performance while maintaining the benefits of cooling, such as pain alleviation. This mini review provides an overview of the acute recovery effects of this innovative method and its potential applications.

Title: Repeated-sprint training in hypoxia induced by voluntary hypoventilation improves running repeated-sprint ability in rugby players.

Authors: Fornasier-Santos C, Millet GP, Woorons X.

Journal: Eur J Sport Sci. 2018 May;18(4):504-512. doi: 10.1080/17461391.2018.1431312. Epub 2018 Feb 5. PMID: 29400616.

Link to Pubmed: Repeated-sprint training in hypoxia induced by voluntary hypoventilation improves running repeated-sprint ability in rugby players.

Abstract: Purpose: The goal of this study was to determine the effects of repeated-sprint training in hypoxia induced by voluntary hypoventilation at low lung volume (VHL) on running repeated-sprint ability (RSA) in team-sport players. Methods: Twenty-one highly trained rugby players performed, over a 4-week period, seven sessions of repeated 40-m sprints either with VHL (RSH-VHL, n = 11) or with normal breathing (RSN, n = 10). Before (Pre-) and after training (Post-), performance was assessed with an RSA test (40-m all-out sprints with a departure every 30 s) until task failure (85% of the reference velocity assessed in an isolated sprint). Results: The number of sprints completed during the RSA test was significantly increased after the training period in RSH-VHL (9.1 ± 2.8 vs. 14.9 ± 5.3; +64%; p < .01) but not in RSN (9.8 ± 2.8 vs. 10.4 ± 4.7; +6%; p = .74). Maximal velocity was not different between Pre- and Post- in both groups whereas the mean velocity decreased in RSN and remained unchanged in RSH-VHL. The mean SpO2 recorded over an entire training session was lower in RSH-VHL than in RSN (90.1 ± 1.4 vs. 95.5 ± 0.5%, p < .01). Conclusion: RSH-VHL appears to be an effective strategy to produce a hypoxic stress and to improve running RSA in team-sport players.

Title: Application of carbon dioxide to the skin and muscle oxygenation of human lower-limb muscle sites during cold water immersion

Authors: Yoshimura M, Hojo T, Yamamoto H, Tachibana M, Nakamura M, Tsutsumi H, Fukuoka Y.

Journal: PeerJ. 2020 Aug 21;8:e9785. doi: 10.7717/peerj.9785. PMID: 32884861; PMCID: PMC7444506.

Link to full text: Application of carbon dioxide to the skin and muscle oxygenation of human lower-limb muscle sites during cold water immersion

Abstract: Background: Cold therapy has the disadvantage of inducing vasoconstriction in arterial and venous capillaries. The effects of carbon dioxide (CO2) hot water depend mainly on not only cutaneous vasodilation but also muscle vasodilation. We examined the effects of artificial CO2 cold water immersion (CCWI) on skin oxygenation and muscle oxygenation and the immersed skin temperature. Subjects and methods: Fifteen healthy young males participated. CO2-rich water containing CO2 >1,150 ppm was prepared using a micro-bubble device. Each subject's single leg was immersed up to the knee in the CO2-rich water (20 °C) for 15 min, followed by a 20-min recovery period. As a control study, a leg of the subject was immersed in cold tap-water at 20 °C (CWI). The skin temperature at the lower leg under water immersion (Tsk-WI) and the subject's thermal sensation at the immersed and non-immersed lower legs were measured throughout the experiment. We simultaneously measured the relative changes of local muscle oxygenation/deoxygenation compared to the basal values (Δoxy[Hb+Mb], Δdeoxy[Hb+Mb], and Δtotal[Hb+Mb]) at rest, which reflected the blood flow in the muscle, and we measured the tissue O2 saturation (StO2) by near-infrared spectroscopy on two regions of the tibialis anterior (TA) and gastrocnemius (GAS) muscles. Results: Compared to the CWI results, the Δoxy[Hb+Mb] and Δtotal[Hb+Mb] in the TA muscle at CCWI were increased and continued at a steady state during the recovery period. In GAS muscle, the Δtotal[Hb+Mb] and Δdeoxy[Hb+Mb] were increased during CCWI compared to CWI. Notably, StO2values in both TA and GAS muscles were significantly increased during CCWI compared to CWI. In addition, compared to the CWI, a significant decrease in Tsk at the immersed leg after the CCWI was maintained until the end of the 20-min recovery, and the significant reduction continued. Discussion: The combination of CO2 and cold water can induce both more increased blood inflow into muscles and volume-related (total heme concentration) changes in deoxy[Hb+Mb] during the recovery period. The Tsk-WI stayed lower with the CCWI compared to the CWI, as it is associated with vasodilation by CO2.

Title: A Novel Bathing Therapeutic Approach for Diabetic Foot Ulcers

Authors: Tappia PS, Hiebert B, Sanjanwala R, Komenda P, Sathianathan C, Arneja AS, Ramjiawan B.

Journal: Applied Sciences. 2021; 11(18):8402. https://doi.org/10.3390/app11188402

Link to full text: A Novel Bathing Therapeutic Approach for Diabetic Foot Ulcers

Abstract: Ineffective healing and treatment of foot ulcers can lead to an infection and gangrene of the wound area that ultimately results in the loss of the limb. The incidence of foot ulcers is higher in patients with diabetes, peripheral vascular disease and kidney disease. Accordingly, this study was undertaken to assess the ability of foot bathing in CO2-enriched water to heal foot ulcers. The design was a double-blinded, randomized, placebo-controlled study. Patients with at least one foot ulcer were randomized to receive either a treatment with bath therapy at 37 ± 0.5 °C containing either 1000–1200 ppm CO2-enriched tap water (the intervention) or non-carbonated tap water at 37 ± 0.5 °C (the control group). Treatment was conducted three times/week for 15 min per session for up to 16 weeks for a total of 48 treatment sessions. Before and at the end of every treatment month, wound size, wound area oxygenation and the ankle brachial index were measured. In addition, the McGill pain questionnaire was conducted. Blood was also collected at these time points (for a total of five collections) for the measurement of different biomarkers. While no significant differences (p < 0.05) in the group/time interaction effect were observed, a clear separation within the wound area reduction/wound area/oxygenated Hb outcomes was seen between placebo (control) and treatment (CO2) group. This pilot study is suggestive that bathing in CO2-enriched water may accelerate the healing of foot ulcers.

Title: Effect of Carbon Dioxide Therapy on Diabetic Foot Ulcer

Authors: Shalan, N. , Al-Bazzaz, A. , Al-Ani, I. , Najem, F. and Al-Masri, M.

Journal: Journal of Diabetes Mellitus, 5, 284-289. doi: 10.4236/jdm.2015.54035.

Link to full text: Effect of Carbon Dioxide Therapy on Diabetic Foot Ulcer

Abstract: Ulceration of diabetic foot represents one of the most concerning complications associated with uncontrolled blood sugar in diabetes mellitus. The aim of this study is to evaluate the condition of twenty-two diabetic patients with different degrees of ulceration in their feet after daily secessions of carbon dioxide therapy. Blood flow to the affected foot was measured by Doppler; also the size, color, degree of ulceration and sensation of the ulcerative area were all evaluated. Results showed improvement of blood flow to the affected foot as well as improvement in the sensation and color of the ulcerative area. It was concluded that carbon dioxide therapy of diabetic foot was promising and needed thorough investigation to be brought widely into application.

Title: The Effectiveness of Dry Carbon Dioxide Baths in Menopausal Syndrome: a Randomized Clinical Study

Authors: Anzhela N. Chekhoeva, Georgy E. Zangionov, Alina B. Bugulova, Alan S. Tsogoev, Olga O. Borisevich, Natalya V. Kotenko.

Journal: Вестник восстановительной медицины. 2024;23(4):55-61. doi:10.38025/2078-1962-2024-23-4-55-61

Link to full text: The Effectiveness of Dry Carbon Dioxide Baths in Menopausal Syndrome: a Randomized Clinical Study

Abstract: INTRODUCTION. Climacteric syndrome is characterized by significant disorders in the nervous, musculoskeletal, urinary and cardiovascular systems in women of the perimenopausal and postmenopausal periods. The main reason is a sharp decrease in estrogen levels. Menopausal hormone therapy is often used for treatment, but due to contraindications and complications, it does not always completely solve the problem. This has sparked interest in alternative treatments such as dry carbon dioxide baths. AIM. To study the effectiveness of using dry carbon dioxide baths in women with menopausal syndrome and evaluate their impact on the neurovegetative, metabolic and psycho-emotional state of these patients. MATERIALS AND METHODS. A prospective randomized study was conducted involving 70 patients with moderate climacteric syndrome aged from 48 to 60 years. Using a simple randomization method, the women were divided into 2 groups: 35 patients of the main group received 10 procedures of dry carbon dioxide baths with a CO2 concentration of 15–20 %, temperature 28–32 °C, lasting 15–20 minutes, 35 patients of the control group did not receive any treatment. To assess the effectiveness of treatment, a modified Kupperman-Uvarova menopausal index, an assessment of the effect of “hot flashes” on daily life on the HFRDIS scale, as well as daily blood pressure monitoring (SMAD) were used. RESULTS AND DISCUSSION. After treatment, patients in the main group observed a significantly significant (p < 0.05) improvement in the patients’ condition in the form of a decrease in integral indicators of the modified menopausal index and an assessment of the impact of hot flashes on daily activity on the HFRDIS scale by 28.2 and 43.1 %, respectively, as well as in the form of a decrease in average daily systolic blood pressure by 13.7 %. CONCLUSION. The use of dry carbon dioxide baths is recommended for use in women with moderate climacteric syndrome, since this method significantly improves the quality of life of patients and is an effective non-drug that can reduce the drug load on the body of a woman suffering from neurovegetative disorders.