Influence of ventilator settings on patient- ventilator synchrony during pressure support ventilation with different interfaces

Objective: To evaluate patient-ventilator interaction during pressure support ventilation (PSV) delivered with three interfaces [endotracheal tube (ET), face mask (FM), and helmet (H)] at different pressurization times (Time_press), cycling-off flow thresholds (Trexp), and respiratory rates (RR) in a bench study, and with FM and H in a healthy volunteers study. Design: Bench study using a mannequin connected to an active lung simulator, and human study including eight healthy volunteers. Measurements: PSV was delivered through the three interfaces with three different RR in the bench study, and through FM and H at two different RR in the human study. The mechanical and the neural RR, Ti, Te, inspiratory trigger delay (Delaytrinsp), pressurization time, and expiratory trigger delay were randomly evaluated at various ventilator settings (Time_press/Tr_exp: 50%/25%, default setting; 20%/5%, slow setting; 80%/60%, fast setting). Results: Bench study: patient-ventilator synchrony was significantly better with ET, with lower Delaytrinsp and higher time of assistance (P<0.001); the combination Time_press/Tr_exp 20%/5% at RR 30 produced the worst interaction, with higher rate of wasted efforts (WE) compared with Time _press/Tr_exp 80%/60% (20%, 40%, and 50% of WE versus 0%, 16%, and 26% of all spontaneous breaths, with ET, FM, and H, respectively; P<0.01). In both studies, compared with H, FM resulted in better synchrony. Conclusion: Patient-ventilator synchrony was significantly better with ET during the bench study; in the human study, FM outperformed H.