Resting oxygen consumption and ventilation in cystic fibrosis

Resting oxygen consumption (V_o2) and minute ventilation (V_E) were measured on nine control subjects and 13 patients with cystic fibrosis (CF). In patients with CF, _O2 was 20% higher (P < 0.01) when expressed per m² and 47% higher (P < 0.001) when expressed per kg body weight, and _E was 58% higher when expressed per m² and 94% higher when expressed per kg body weight (P < 0.001) than in control subjects. Repeated measures of _O2 and _E were highly reproducible over 2 hours (within‐subject coefficients of variation: in controls, _O2 = 5.5%, _E = 7.4%; in CF, _O2 = 3.1%, _E = 5.1%). Since the increases in _E were greater than those in _O2, the ventilatory equivalent (_E/_O2) 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_CO2 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).