Use of a human patient simulator for apnea studies: a preliminary in vitro trial

BACKGROUND: Modern human patient simulators (HPSs) could be used for researching critical scenarios such as apnea oxygenation. We aimed to study the use of a high-fidelity HPS to assess prolonged apnea using various oxygenation strategies with a simple high-flow nasal cannula (15 L/min). METHODS: An experimental simulation study using an HPS (CAE Healthcare™) was conducted after obtaining approval from the Institutional Review Board. The HPS responded according to real-time physiologically modeled responses to external gases, such as oxygen (O(2)). Apnea experiments were performed with different physiological settings, such as shunt fraction (5%) and O(2) consumption (250, 500, and 750 ml/min). The following four apnea experiments were conducted: no oxygenation (NO), apnea oxygenation alone (AO), preoxygenation alone (PO), and para-oxygenation (PAO). The time to 92%, 75%, and 50% saturation was recorded. Alveolar and arterial gas levels were recorded till 50% saturation. RESULTS: At 250 ml/min, PO (1121 s) and PAO (1274.5 s) had a significantly longer time to 50% saturation (400% increase) compared to NO (222.5 s) and AO (239 s). A similar trend was observed for the time to 92% and 75% saturation. At higher O(2) consumption rates, a shorter time to desaturation was observed. CONCLUSIONS: Apnea trends in the HPS correlated with similar prior human experiments. AO without preoxygenation was found to provide no additional benefit. Preoxygenation with high-flow O(2) via nasal cannula prolonged the time to desaturation in the PAO more than PO scenario. Therefore, HPSs can be used in future studies where patient safety is a concern.