Fig. 5
From: Influence of different noninvasive oxygenation support devices on tidal volume
Effect of various oxygenation devices on inspiratory driving pressure in bench model. Inspiratory flow depends on the pressure difference between the mouth pressure and the alveolar pressure, which results from the negative pressure produced by respiratory muscles contraction during spontaneous breathing. As compared to the use of a non-rebreather oxygen mask (O2-MASK), during which the mouth pressure (Pmouth) remained constant, there was a drop in Pmouth with the use of high-flow oxygen through nasal cannula (HFNC) and continuous positive airway pressure (CPAP), decreasing the inspiratory driving pressure (ΔP), and rise in Pmouth with the use of NIV conducted with an oro-nasal mask (Mask-NIV), leading to an important increase in the inspiratory driving pressure. Alveolar pressure was computed using the following equation: Palv = Paw−(Raw x V′). O2-mask: non-rebreather oxygen mask; HFNC: high-flow oxygen through nasal cannula; CPAP: continuous positive airway pressure; Mask-NIV: noninvasive ventilation with oronasal mask; Palv: alveolar pressure; Pmouth: mouth pressure; Pmus: muscle pressure; ∆P: driving pressure