THE SENSITIVITY OF THE RESPIRATORY CENTER TO HYDROGEN ION CONCENTRATION

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Abstract
The ability of the respiratory center to compensate for a fixed acid acidosis (due to hydrochloric or lactic acids) was tested in dogs under barbiturate anesthesia and deprived of the chemoreceptor reflexes by de-nervatipn of the carotid sinus region and section of both vagus nerves. Evidence was obtained of the absence of the chemoreceptor reflexes. The acidosis produced was progressively increased by successive injs. of acid. Before and in between injs. the min. vol. ventilation, the CO2 tension of alveolar air, and the total CO2 conc. of arterial blood were detd. The pH of arterial blood was calculated in all expts. and in one expt. it was also detd. electrometrically by means of a glass electrode. In all of 9 expts. the results were similar: a marked acidosis was compensated by hyperventilation and consequent decrease of the CO2 tension and carbonic acid conc. of arterial blood. The CO2 tension was inversely proportional to the min. vol. ventilation. The pH of arterial blood remained constant varying on the avg. [plus or minus]0.008 (in 1 expt. only [plus or minus]0.001). With the chemoreceptor mechanisms absent the respiratory center was considered the regulatory mechanism that maintained the pH within such limits and these limits were considered the indication of the sensitivity of the respiratory center to changes in pH. A theory is presented postulating 2 independent mechanisms in the respiratory center, one responding to increased acidity and the other responding reflexly.