title: Correlation of the oxygen cost of breathing and length of weaning from mechanical ventilation.
abstract: We studied 20 patients (ages 43 to 84 yr), whose forced vital capacity, peak negative inspiratory pressure and alveolar-arterial gradient indicated that they were unlikely to be withdrawn rapidly from mechanical ventilation. Their mean oxygen consumption (VO2) during controlled ventilation (CV) was 292 +/- 21 (SEM) ml/min. During spontaneous ventilation (SV) through endotracheal tube and ventilator circuit, the VO2 rose significantly (p less than .001) to 323 +/- 20 ml/min. The oxygen cost of breathing (OCB) (the difference in VO2 between CV and SV) and the OCB as a fraction of the oxygen consumed during SV (OCB/VO2 SV) both correlated significantly by linear regression analysis with the total time to wean in days (-11.6 + 0.93 for OCB, r = .79; and -12.6 + 293.1 for OCB/VO2 SV, r = .84, p less than .001 for both). As the OCB was correlated with the total wean time, this variable may be a useful index of the effect of many influences on the weaning process.
mesh_terms: D000328:Adult; D000368:Aged; D002153:Calorimetry, Indirect; D003422:Critical Care; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D012119:Respiration; D012121:Respiration, Artificial; D014797:Vital Capacity