Research Information System
CHEST, no.6, pp.1424-1431, 2006 (SCI-Expanded)
Background: Noninvasive ventilation (NIV) is increasingly used in intensive care medicine, but only little information is available bow different NIV interfaces affect the performance of a ventilatory system. Therefore, we compared delay times, pressure time products (PTPs), and wasted efforts during inspiration among patients receiving invasive ventilation and NIV with a belmet (NIV-H) or a face mask (NIV-FM). Methods: Using an in vitro lung model capable of simulating spontaneous breathing, gas flow and airway pressure were measured with varying positive end-expiratory pressure and pressure support (PS) levels. Wasted efforts were determined while lung compliance, respiratory rate (RR), continuous positive airway pressure (CPAY), and PS levels were changed. Results: Delay times were more than twice as long with a helmet compared to NIV-FM or invasive ventilation (p < 0.001), but decreased during NIV-H with increasing CPAF (p < 0.001) and PS levels (p < 0.001). During the initial inspiratory phase, PTP was smaller with NIV-H compared to NIV-FM or invasive ventilation, but not so when a complete inspiration with PS was evaluated. Wasted efforts occurred earlier during NIV-H and were aggravated with rising PS, RR, and compliance. Conclusions: Although delay times are prolonged during NIV-H, PTP is initially smaller compared to NIV-Fm and invasive ventilation, indicating less work of breathing due to the high volume the patient can access. Increasing the CPAP or PS level decreases delay times in NIV-H and should therefore be considered whenever possible. Wasted inspiratory efforts occurred at higher RRs and should carefully be monitored during NIV.