Effect of oxygen tubing connection site, changes of the inspiratory positive airway pressure and tidal volume on inspired oxygen concentration during noninvasive positive pressure ventilation

Abstract

We evaluated the effects of administering oxygen through nasal catheter inside the mask or through the mask on inspired oxygen concentration in order to find better ways of administering oxygen to improve the inspired oxygen concentration in non-invasive positive pressure ventilation (NPPV). A human face model was used to simulate the human face, and the model of the double lumen endotracheal tube was used to simulate the bilateral nasal cavity and trachea, and then a model was constructed to allow simulated NPPV. The changes of FIO₂were measured in different pressure (constant tidal volume) and different tidal volume (constant pressure) conditions under the way of administering oxygen through nasal catheter inside the mask or through the mask. The effects on FIO₂were measured in different pressure (constant tidal volume) and different tidal volume (constant pressure) conditions under same way of administering oxygen. The FIO₂was (35.4 ± 1.7)% when oxygen was administered through the mask, but a higher FIO₂was achieved with the oxygen injected into the mask [(52.4 ± 2.1)%, and oxygen flow of 5 L/min, P<0.05]. The oxygen concentration declined with the increase of inspiratory positive airway pressure (IPAP) on the condition of administering oxygen through the mask on constant tidal volume. The FIO₂at IPAP 16 cmH₂O (1 cmH₂O=0.098 kPa) was higher than that at IPAP 8 cmH₂O, and the FIO₂at IPAP 20 cmH₂O was higher than those at IPAP 8 cmH₂O and 12 cmH₂O, P<0.05. The oxygen concentration increased with the tidal volume increase on the condition of administering oxygen through the mask on constant IPAP. The changes of tidal volume and IPAP had no effects on FIO₂on the condition of administering oxygen through nasal catheter inside the mask. Administering oxygen through nasal catheter inside the mask during NPPV can increase FIO₂and conserve oxygen. This study provides theoretical basis for the development of newer masks.