Use of the oxygen cost of breathing as an index of weaning ability from mechanical ventilation.

The oxygen cost of breathing (which is the difference in oxygen consumption measured during controlled ventilation and again during spontaneous ventilation) was measured in 30 patients between the ages of 17 and 96 years at the time of commencement of weaning from mechanical ventilation. There was a significant exponential correlation between the oxygen cost of breathing in ml/m2/min and the oxygen cost of breathing as a percentage of total oxygen consumption during spontaneous ventilation (OCB/VO2SV%) and the duration of weaning in days.