CARBON-DIOXIDE RESPONSE LINES IN YOUNG-ADULTS - LIMITS OF NORMAL RESPONSE

Abstract

The mean .+-. SE slope of the line relating PCO2 [CO2 tension] to minute volume of ventilation in 126 normal, young adults was 2.60 .+-. 0.107 l/min .cntdot. mm Hg. Although a wide range of responses was noted, 80% of the subjects had a value for the slope between 1.5-5.0 l/min .cntdot. mm Hg, with 16.6% having values lying below and 4% above this range. Women were significantly less responsive than men. Low, but significant, correlations were found between the slope and vital capacity, and between the slope and maximal breathing capacity, but not between the slope and height, weight, age or smoking habits. Additional findings included an increase in the slope with prolonged rebreathing, possibly due to a peripheral chemoreceptor effect; absence of metabolic acidosis during 4 min of rebreathing; excellent short-term reproducibility of results in 111 subjects and good longer-term reproducibility in most of 10 subjects retested 9-24 mo. later.