We measured oxygen consumption (V̇O2) during spontaneous breathing with continuous positive airway pressure (CPAP), assist control ventilation (AC), and control ventilation during muscle relaxation (AC-MR) in eight patients undergoing resuscitation from cardiopulmonary failure. V̇O2 decreased in all eight patients between CPAP and AC-MR; mean V̇O2 (255 ± 92 ml/min) on CPAP exceeded that on AC-MR (209 ± 79 ml/min) (p < 0.005). Compared with CPAP, AC without MR reduced V̇O2 in five of eight patients and mean V̇O2 (227 ± 59 ml/min) tended to decrease (p = 0.14); clinical examination did not distinguish patients requiring MR to reduce V̇O2 further. If V̇O2 on CPAP approximates V̇O2 during spontaneous breathing, the difference between CPAP and AC-MR (V̇O(2resp)) represents the decrement of V̇O2 that can be obtained during muscle rest. Both V̇O(2resp) and the mechanical work performed by the ventilator on the respiratory system were increased to about five times the efficiencies reported for normal patients, but V̇O(2resp) did not correlate with the mechanical work because of a wide range of respiratory muscle efficiencies. These efficiencies are less than those reported in normal patients, which may reflect the effect of sepsis, acidemia, hypoxia, or other conditions in these patients. We conclude that mechanical ventilation with muscle relaxation reduces V̇O2 by more than 20%; beyond stabilizing pulmonary gas exchange, these interventions preserve limited O2 delivery (Q̇O2) for other vital organs.
|Original language||English (US)|
|Number of pages||5|
|Journal||American Journal of Respiratory and Critical Care Medicine|
|State||Published - Jan 1 1995|
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine
- Critical Care and Intensive Care Medicine