Increased CO2 drive for ventilation in healthy human subjects may interfere with their ability to control lung...

Influence of increased CO2 drive for ventilation on the ability to judge lung volume was studied in seven healthy subjects. The psychophysical relationships between the objective and subjective magnitudes of lung volume were tested during air breathing and at two levels of hypercapnia (breathing 4% and 6% CO2 in oxygen). The relationships, described by linear regression, were analysed with respect to correlation coefficient, slope and intercept of the regression line. Slope and intercept seemed to decrease as the inspired CO2 mixture increased. Statistically significant difference was found only between air and inhalation of 6% CO2 in oxygen. Correlation coefficient remained unaffected by an increase in PCO2. These results indicate that an experimental increase in PCO2 caused by 6% CO2 inhalation alters the behavioural respiratory control in healthy human subjects.