THE RESPIRATORY RESPONSE TO CARBON DIOXIDE IN HEALTH AND IN EMPHYSEMA

Abstract

While most investigations have reported the respiratory response to CO2 in terms of ventilation, this may be inaccurate because of modifications in the ventilatory capacity and the degree of airway obstruction. The response of the respiratory muscles determined by measuring the total amount of mechanical work done by these muscles, should be a more accurate measure of respiratory center activity. The respiratory response to CO2 was assessed in terms of ventilation, O2 consumption and total mechanical work, in 12 normal and 10 emphy-sematous subjects. Evidence is presented to suggest that incremental changes in total mechanical work are a more accurate gauge of the respiratory response to CO2 than are increments of ventilation or O2 consumption. The response of the respiratory center and muscles of patients with emphysema, when measured in terms of total mechanical work done, is lower than that of normal subjects. The response of the emphysematous subjects with CO2 retention at rest while breathing room air, tends to be depressed below that of the patients who were normocapnic.