On the Influence of Carbon Dioxide Inhalation upon the Gaseous Metabolism and the Circulation

Abstract

On discussing the data above stated, it is obvious that the augmentation in the respiratory volume during CO₂ inhalation is based on the accumulation of CO₂ in the blood and tissues, because as is well known, the respiratory centre is very sensitive to the increased H-concentration in the blood. That the oxygen consumption is lowered by CO₂ inhalation is presumably due to diminished oxidation of tissues caused by acidosis through CO₂ inhalation. The fact, confirmed by Lehmann, ¹⁸⁾ Chvostec, ¹⁹⁾ Raeder, ²⁰⁾ Loewy and Münzer, ²¹⁾ and Ito²²⁾ that in rabbits when the animals undergo an intravenous injection of hydrochlorid acid, the oxygen consumption diminishes, is accounted for by the acidosis. It is placed beyond doubt by the experiments of Ito, one of us (Hayasaka)²³⁾ and Dürr²⁴⁾ that an acidosis, deteriorating the oxidation in tissues, decreases the oxygen consumption.
As already pointed out it is thought to be a strange phenomenon that CO₂ output is appreciably decreased, in spite of profuse intake of CO₂. But in Eppinger's²⁵⁾ experiments a dog (14 kilos body weight) showed after the inhalation of air containing 12% CO₂ for 90 minutes an accumulation of 7.68 liters CO₂, of which only 6% was exhausted in 1 hour after the cessation of CO₂ inhalation, and an another dog (12.6 kilos body weight) during the inhalation of air containing 14.3% CO₂ lasting 90 minutes, an accumulation of 9.01 liters CO₂, of which only 19% was discharged in 1 hour thereafter. In brief, the majority of inspired CO₂ has been retained in the tissues, that is, the latter have a considerable power of combination with CO₂. This is in accordance with the fact observed by Stinzing, ²⁶⁾ that CO₂ was evolved in an amount of about 180% from a muscle by boiling it. Thus, although the process, in which CO₂ is combined with the tissues, is accounted for with difficulty, it has been illustrated by Eppinger²⁵⁾ that even the quantity of CO₂ which is only physically dissolved in the human tissues, would amount to 25-30 liters, if the profuse water content of the tissues and its absorbent coefficient of CO₂ at body temperature are taken into consideration.
Thus, when we reflect on these presumptions, it is quite right that the carbon dioxide which is accumulated in the tissues after CO₂ inhalation should be considerable in amount. In reviewing our data, the difference obtained by reducing CO₂ output per minute from the sum of the amount of inspired CO₂ and the physiologically produced CO₂ amount per minute, i. e. the accumulated CO₂ amount in the body per minute is culculated as 333-913c. c., as is shown in Table III.
As above stated, through CO₂ inhalation the oxygen consumption is decreased, but CO₂ output is more intensively diminished, whereby it is quite natural that the respiratory quotient is lowered. The fact that the pulse rate is increased owing to CO₂ inhalation can be regarded chiefly as a sign following the accelerated respiratory function, but may partly be provoked by the stimulation of the sympathetic nervous system due to the increased secretion of adrenaline, which results through acidosis aroused by the CO₂ accumulation in the body, as Macleod²⁷⁾ has maintained.
The evidence that the minute volume is augmented by CO₂ inhalation falls in with the condition that the cardiac function ought to be accelerated in order to supply plenty of oxygen to make good the decreased oxidation of the tissues, which is presumed from the lowering of the oxygen consumption.