Theoretical study of inspiratory flow waveforms during mechanical ventilation on pulmonary blood flow and gas exchange

The effect of varying inspiratory flow waveforms on pulmonary mechanics in critically ill patients

PURPOSE

Ten mechanically ventilated patients were evaluated to determine the effect of three different inspiratory flow patterns on pulmonary mechanics.

MATERIALS AND METHODS

Ten consecutive mechanically ventilated critically ill patients with acute respiratory failure admitted to the intensive care unit were evaluated to assess the effects of decelerating, square, and sine waveforms on pulmonary mechanics. The variables measured were peak airway pressure (PaW), pleural pressure (Ppl), change in peak airway pressure (dPaW), inspiration time/total ventilation cycle time (Vi/tot), dynamic compliance (Cdyn), respiratory rate (RR), minute ventilation (Ve), and work of breathing (WOB).

RESULTS

The PaW, Ppl, and dPaW (cm H2O) were significantly lower using the decelerating inspiratory flow waveform (P<.05) compared with sine or square waveform patterns. Ti/Ttot was also lower with the decelerating waveform (P<.05) with better dynamic compliance compared with the other waveforms (P<.10).

CONCLUSIONS

These results indicate that critically ill mechanically ventilated patients show improved respiratory mechanics with decelerating inspiratory waveform that may have beneficial clinical implication.