Effect of mechanical ventilation with end-inspiratory pause on blood-gas exchange.

The effects of end-inspiratory pause (EIP) on gas exchange were measured in 10 adult patients with acute respiratory insufficiency while maintained on mechanical ventilation. Four inspiratory patterns were studied with a constant tidal volume (10 to 15 ml/kg body weight), respiratory rate (9 to 12 breaths/min), FIO2 (0.5) and end-expiratory pressure. Inspiratory flow rate (V insp) and EIP time were varied to produce a control pattern (V insp = 60 L/min, EIP = 0), 2 EIP patterns of 0.6 and 1.2 seconds with a similar V insp and a "slow" flow pattern (V insp = 30 L/min) without EIP. The control pattern was applied before and after each study period. Arterial oxygenation was unchanged with both EIP and "slow" flow patterns when compared to control. Dead-space ventilation (VD/VT) and Paco2 were significantly decreased (p less than 0.01) as EIP was increased from 0 to 1.2 seconds, but remained unchanged with slow inspiratory flow. Thus, EIP improved the efficiency of ventilation with no apparent improvement in oxygenation in patients with acute respiratory insufficiency.