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