Subcutaneous and muscular (cranial tibial) tissue PO₂ and PCO₂ in CO₂ vapour bath were measured on rabbit by means of Medical Mass Spectrometry, MEDSPECT II, Chemetron, U. S. A.
Subcutaneous PO₂ increased by 30% during CO₂ vapour bath of 5L/min at 37°C and muscular PO₂ increased by 50% after CO₂ vapour bath, keeping the level at least for 2 hours.
Ideal elevation of PO₂ level was observed in vapour bath of 1L/min at 37°C for 30min.
A number of factors causing an elevation of PO₂ in tissue by topically applied CO₂ are to be thought, such as a vasodilating effect, pH-lowering, shift to right of oxygen dissociation curve and so on.
It is assumed that the PO₂ elevation together with an improved tissue perfusion could ameliorate complains of patients suffering from degenerative pathology and peripheral arterial insufficiency by stimulating patients' own potential curability.

Tissue partial pressure of O₂ (PO₂) and CO₂ (PCO₂) in CO₂ vapour bath were measured on rabbit by means of Medical Mass Spectrometry, MEDSPECT II, Chemetron, U. S. A.
Topical absorption of CO₂ through the skin exposed to CO₂ gas was confirmed by comparing the subcutaneous tissue PO₂ and PCO₂ in CO₂ vapour bath with those of CO₂ free head area; subcutaneous tissue PO₂ and PCO₂ were elevated by 92% and 48% respectively in the former, whereas subcutaneous tissue PO₂ and PCO₂ in the latter were found no change. Lowering of subcutaneous pH was found simultaneously with the elevation of PCO₂ in CO₂ vapour bath, contributing largely to the elevation of PO₂ in response to CO₂ accumulation.
Subcutaneous tissue PCO₂ reaches a saturated level in about 30 minutes regardless of each CO₂ flow rate varying from 1 to 5 liters per minute. Too much application of CO₂ gas is not always so effective as expected. Changes of PCO₂ and PO₂ were not in proportion to a rise in temperature from 33.4°C to 41.5°C on the same rabbit. It is, therefore, suggested that the optimal application of CO₂ gas on rabbits is at their indifferent temperature of around 37°C.
The optimal conditions for rabbits would be suggested as 1 liter of CO₂ gas per minute at 37°C for 30 minutes in consideration of the side effects on both circulatory and respiratory systems.
Based on the experimental data, conditions of 30 liters per minute at 40°C for 30 minutes would be recommended in clinical application of CO₂ gas cabin.

We examined Tissue Partial Pressure of O₂ (PO₂) and CO₂ (PCO₂), changes of Pulse Rate (P. R.) and Blood Pressure (B. P.) in a bath at different temperature using rabbit. Expeilmental method;
A rabbit about 2kg body weight is taken a bath at each temperature of 37°C, 40°C, and 43°C for 30 minutes by means of constant-temperature water bath method under the anesthesia of venous drip of NEMBUTAL® (Pentobarbital Sodium).
Teflon catheters for tissue gas analyses are inserted to the Cranial tibial muscle and the over-lying subcutaneous tissue. Tissue PO₂ and PCO₂ in a bath are measured by Medical Mass Spectrometry (MEDSPECT II, Chemetron, U. S. A.). The changes of B. P. and P. R. are recorded simultaneously.
Results and Discussion;
1, In a bath at 37°C, there are no changes on both B. P. and P. R., but the elevation of PO₂ is a little, leading to an insignificant effect.
2, In a bath at 40°C, subcutaneous tissue PO₂ and muscular tissue PO₂ are found elevated by 74% and 53% respectively. P. R. is found increased by 34%, and B. P. is found reduced by 8%. This reduce of B. P. is due possibly to the peripheral vasodilatation. From the standpoint of a peripheral circulation, bath temperature of 40°C is thought to be efficient in washing out metabolites, leading to recovery from fatigue.
3, In a bath at 43°C, subcutaneous tissue PO₂ and muscular tissue PO₂ are found elevated by 74% and by 53% respectively. And tissue PCO₂ are found elevated by 65% in subcutaneous tissue and by 64% in muscular one; 13% up from those found in a bath at 40°C, leading to some fatigue. B. P. is elevated by 16% and P. R. is increased by 69% respectively in a bath at 43°C. Arrhythmia occurs sometimes. It is, therefore, assumed that the man who has a handicap on the circulation system and the elder who has arteriosclerosis in his base should not take a bath at high temperature and/or for a long time.

Actual changes in tissue partial pressures of each gas and tissue perfusion with serial artificial CO₂ bathing were evaluated by means of medical mass spectrometry using 5 rabbits.
An artificial CO₂ bath was prepared by adding “BUB”-KAO, a 50g sodium hydrogencarbonate and succinic acid tablet producing fine CO₂ bubbles in water of constant temperature 20-litre tub at 36-37°C.
Regional tissue perfusion volume was determined on the basis of a clearance curve for Argon tissue partial pressure which was monitored by an on-line computer system with mass spectrometry.
Increase in subcutaneous tissue PCO₂ changed from 27% to 10%, and in PO₂ from 12% to 5% on average by serial bathing every day for 4 weeks, on the other hand tissue perfusion volume was increased in 3 out of 5 cases; from 20.85±3.56 (X±SE) ml/100g/min, SD=6.71, p<0.05 to 25.23±8.00 (X±SE) ml/100g/min, SD=6.96, p<0.05.
CO₂ has been shown to be locally absorbed through the skin resulting in the elevation of subcutaneous tissue CO₂ partial pessure which decreases depending on the tissue perfusion irrespective of metabolic processes. It is, therefore, assumed that the elimination of absorbed constituents by serial bathings is not caused by a decrease in the percutaneous absorption rate but an increase in washing out rate by the improved tissue perfusion.