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

The Efficacy of Carbon Dioxide Paste in Alleviating Pain in Patients After Neck Dissection: Protocol for a Double-Blinded, Randomized Controlled Trial

BACKGROUND

Head and neck cancers that cause severe aesthetic and functional disorders normally metastasize to the cervical lymph nodes. Patients with cervical lymph node metastasis are undergoing neck dissection. Shoulder complaints are common after neck dissection, with patients reporting symptoms such as pain, weakness, shoulder droop, and disability. However, no safe and effective treatment is available for this condition at present. We will conduct a double-blinded, randomized controlled trial to evaluate the efficacy of carbon dioxide (CO2) paste in relieving pain in patients after neck dissection.

OBJECTIVE

This will be the first clinical study to compare the efficacy of CO2 paste with placebo in relieving postoperative pain in patients who underwent neck dissection.

METHODS

We will perform this trial at the Kobe University Hospital in Japan. Patients will be randomized 1:1 into the CO2 paste and control groups. Patients in the CO2 paste group will have the CO2 paste applied to the cervical surface skin for 10 minutes once per day for 14 consecutive days. The primary end point of the study is a change in the visual analog scale (VAS) scores of neck pain from baseline on day 1 (preapplication) to the end of drug application (day 15). Secondary end points include changes in the following parameters from baseline on day 1 to the end of drug application (day 15) or the study (day 29): neck pain VAS score (days 1-29), grip strength (days 1-15 and 1-29), VAS scores for subjective symptoms (the feeling of strangulation, numbness, swelling, and warmth in the neck and shoulder region) for days 1-15 and 1-29, whether the VAS score improved more than 30% (days 1-15), the arm abduction test (days 1-15 and 1-29), shoulder range of motion (abduction and flexion) for days 1-15 and 1-29, occurrence of skin disorders, and occurrence of serious side effects. Periodic monitoring will be conducted for participants during the trial. This study was approved by the certified review board of Kobe University.

RESULTS

The intervention commenced in May 2021 and will continue until March 2024. The collected data will provide information on the efficacy of the CO2 paste treatment. The primary end point will be compared using the Wilcoxon test, with the 1-sided significance level set at 5%. Each evaluation item will be summarized. Secondary efficacy end points will be analyzed to provide additional insights into the primary analysis. Findings based on the treatment effects are expected to be submitted for publication in 2025.

CONCLUSIONS

This trial will provide exploratory evidence of the efficacy and safety of CO2 paste in relieving pain in patients after neck dissection.

TRIAL REGISTRATION

Japan Registry of Clinical Trials (jRCT) identifier: jRCTs051210028; https://jrct.niph.go.jp/en-latest-detail/jRCTs051210028.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/50500.

The Tissue Response to Hypoxia: How Therapeutic Carbon Dioxide Moves the Response toward Homeostasis and Away from Instability

Sustained tissue hypoxia is associated with many pathophysiological conditions, including chronic inflammation, chronic wounds, slow-healing fractures, microvascular complications of diabetes, and metastatic spread of tumors. This extended deficiency of oxygen (O₂) in the tissue sets creates a microenvironment that supports inflammation and initiates cell survival paradigms. Elevating tissue carbon dioxide levels (CO₂) pushes the tissue environment toward "thrive mode," bringing increased blood flow, added O₂, reduced inflammation, and enhanced angiogenesis. This review presents the science supporting the clinical benefits observed with the administration of therapeutic CO₂. It also presents the current knowledge regarding the cellular and molecular mechanisms responsible for the biological effects of CO₂ therapy. The most notable findings of the review include (a) CO₂ activates angiogenesis not mediated by hypoxia-inducible factor 1a, (b) CO₂ is strongly anti-inflammatory, (c) CO₂ inhibits tumor growth and metastasis, and (d) CO₂ can stimulate the same pathways as exercise and thereby, acts as a critical mediator in the biological response of skeletal muscle to tissue hypoxia.

Return to training in the COVID-19 era: The physiological effects of face masks during exercise

COVID-19 outbreak has a profound impact on almost every aspect of life. Universal masking is recommended as a means of source control. Routinely exercising in a safe environment is an important strategy for healthy living during this crisis. As sports clubs and public spaces may serve a source of viral transmission, masking may become an integral part of physical activity. This study aimed to assess the physiological effects of wearing surgical masks and N95 respirators during short-term strenuous workout. This was a multiple cross-over trial of healthy volunteers. Using a standard cycle ergometry ramp protocol, each subject performed a maximal exercise test without a mask, with a surgical mask, and with an N95 respirator. Physiological parameters and time to exhaustion were compared. Each subject served his own control. Sixteen male volunteers (mean age and BMI of 34 ± 4 years and 28.72 ± 3.78 kg/m² , respectively) completed the protocol. Heart rate, respiratory rate, blood pressure, oxygen saturation, and time to exhaustion did not differ significantly. Exercising with N95 mask was associated with a significant increase in end-tidal carbon dioxide (EtCO₂ ) levels. The differences were more prominent as the load increased, reaching 8 mm Hg at exhaustion (none vs N95, P = .001). In conclusion, in healthy subjects, short-term moderate-strenuous aerobic physical activity with a mask is feasible, safe, and associated with only minor changes in physiological parameters, particularly a mild increase in EtCO₂ . Subjects suffering from lung diseases should have a cautious evaluation before attempting physical activity with any mask.

The effect of transcutaneous application of gaseous CO2 on diabetic chronic wound healing-A double-blind randomized clinical trial

Chronic wounds in diabetics are difficult to treat, therefore, adjuvant therapies have been investigated. Bathing in CO₂ -rich water (spa therapy) has been known in Europe for decades for its positive effect on peripheral vascular disorders. Recently, much effort has been invested in developing optimal application methods of CO₂ . Uses include subcutaneous injections of CO₂ , bathing in CO₂ -enriched water, and transcutaneous application of CO₂ . To verify the effect of transcutaneous application of gaseous CO₂ on the healing of chronic diabetic wounds, a randomized double-blind clinical research was designed. The research included 30 and 27 wounds in the study and control groups, respectively. In addition to standard treatment, patients in the study group received 20 therapies with medical-grade CO₂ gas and the control group received the same treatment with air. Results showed significantly faster healing in the study group: 20 of the 30 wounds in the study group were healed compared with none in the control group. Mean wound surface and volume in the study group was reduced significantly (surface: 96%, P = .001, volume: 99%, P = .003) compared with a small reduction in the control group (surface: 25%, P = .383, volume: 27%, P = .178). Considering our results, transcutaneous application of gaseous CO₂ is an effective adjuvant therapy in diabetic chronic wound treatment.

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

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.

Trial registration

This study has been registered in the UMIN Clinical Trials Registry (Registration number: UMIN000013641, Date of registration: July 1, 2014).