Effect of different interfaces on fio2 and co2 rebreathing during noninvasive ventilation

Abstract

BACKGROUND: Improving FIO2 and reducing CO2 rebreathing (_VICO2) are the key means to improve the therapeutic efficacy of noninvasive ventilation (NIV). This study aimed to investi-gate the impact of interface design on FIO2 and _VICO2 during NIV. METHODS: A simulated lung model was established to analyze 17 different interfaces. CO2 was injected into the outlet of the simulated lung, and the noninvasive ventilator was connected to the simulated lung to simu-late the application of NIV in patients with COPD with hypercapnia. FIO2 and _VICO2 were calcu-lated by mathematical integration of synchronously collected data pertaining to real-time pressure, flow, oxygen concentration, and CO2 concentration in the breathing circuit. Comparisons were performed between different types (nasal vs oronasal) and models of interfaces as well as between interfaces with different leak positions. Correlation of FIO2 and _VICO2 with inner volume and leakage, respectively, and the correlation between FIO2 and _VICO2 were analyzed. RESULTS: FIO2 levels were significantly different with a nasal or an oronasal mask (0.45 ± 0.05% vs 0.41 ± 0.08%, respectively; P