Noninvasive positive pressure ventilation delivered by helmet vs. standard face mask

Objective. This bench and human study compared large and small helmets with face mask (FM) for delivery of noninvasive positive pressure ventilation. Design. A lung simulator was employed, and the human study involved six healthy subjects. We evaluated a continuous high-flow (CPAP(HF)), low flow (CPAP(LF)), ventilator (CPAP(VENT)) CPAP, and pressure support ventilation (PSV 10 and 20 cmH(2)O). In the human study we used CPAP(HF), CPAP(VENT), and PSV 5 cmH(2)O. PEEP was 5 cmH(2)O. Measurements. In the bench study during CPAP we measured the negative airway pressure time product (area(CPAP)), i.e., the area of airway pressure (Paw) under PEEP and during PSV the pressure airway time product (area(PSV)), i.e., the area of Paw from onset to end of inspiratory flow. In the human study we measured the breathing pattern and work of breathing (WOB). Results. In the bench study during CPAP(LF) the helmets had a lower area(CPAP) than the FM, while during CPAP(HF) the three interfaces had similar area(CPAP). Using CPAP(VENT) and PSV the FM reduced area(CPAP) and increased area(PSV) compared to helmets. At 20 cmH(2)O of PSV using helmets area(PSV) was similar to that obtained at 10 cmH(2)O of PSV using the FM. In human study using CPAP(HF) and CPAP(VENT) the tree interfaces had similar effects on breathing pattern and WOB, while using PSV the FM reduced WOB more than helmets. Conclusions. During CPAP(LF) helmets were more efficient than FM, while during CPAP(HF) the three interfaces were comparable. Using CPAP(VENT) and PSV, FM was more efficient than helmets.