Resting oxygen consumption and ventilation in cystic fibrosis

Resting oxygen consumption (V o 2 ) and minute ventilation (V E ) were measured on nine control subjects and 13 patients with cystic fibrosis (CF). In patients with CF, O 2 was 20% higher ( P < 0.01) when expressed per m 2 and 47% higher ( P < 0.001) when expressed per kg body weight, and E was 58% higher when expressed per m 2 and 94% higher when expressed per kg body weight ( P < 0.001) than in control subjects. Repeated measures of O 2 and E were highly reproducible over 2 hours (within‐subject coefficients of variation: in controls, O 2 = 5.5%, E = 7.4%; in CF, O 2 = 3.1%, E = 5.1%). Since the increases in E were greater than those in O 2 , the ventilatory equivalent ( E / O 2 ) was 32% higher in CF than in controls. We conclude that size‐corrected total energy expenditures and E at rest are higher in patients with CF than in control subjects. Ventilation appears mechanically inefficient but necessary to keep arterial P CO 2 from rising and oxygen saturation from falling at rest. Our results are consistent with observations that these patients have an abnormally large physiological dead space (Featherby et al.: Ann Rev Respir Dis 1969; 102:737).