Cardiovascular, respiratory, and metabolic changes produced by pressure-supported ventilation in intensive care unit patients.

The cardiovascular, respiratory and metabolic effects of pressure-supported ventilation with 7, 14 and 21 cm H2O were studied in 16 spontaneously breathing patients convalescing from severe illness. No statistically significant changes occurred in the hemodynamic variables, although CVP and urine output were increased at the higher levels of pressure support. Minute volume and blood gases did not change. Pressure-supported ventilation was associated with a statistically significant decrease in respiratory rate (p less than .002), a significant increase in tidal volume (p less than .01) and in mean airway pressure (p less than .001). Oxygen consumption, CO2 production, and resting energy expenditure were reduced by 14% to 20%, 17% to 25% and 10% to 18%, respectively, the decrease being proportional to the level of pressure support. These changes of the metabolic variables were not found to be statistically significant.