AMBU Bag Manual Ventilation vs. Transport Ventilator Mechanical Ventilation for Transport

Following cardiac surgery, patients often require ventilation during transport to the intensive care unit (ICU). Most of the time, manual ventilation using an AMBU bag (AMBU INC. MD, USA) is utilized, but some patients need mechanical ventilation due to concern for oxygenation, ventilation, and hemodynamics. The indication to choose mechanical ventilation over manual ventilation is determined on a case-by-case basis, mostly based on providers' experiences or surgical request, because currently there is no clear clinical evidence behind that. With this clinical study, the investigators intend to build up clinical evidence by comparing oxygenation, ventilation, hemodynamics, and cardiac functions between two arms: manual ventilation using AMBU bag arm and mechanical ventilation using a transport ventilator. Objective: In this study, the investigators plan to compare the effects of transport ventilators (Hamilton C1: Bodaduz, Schweiz) and AMBU bag manual ventilation on oxygenation, ventilation, biventricular function, and hemodynamics. This is a two-arm study. 1. To assess pre and post transport PaO2/FiO2 (P/F ratio), PaCO2, biventricular function, and mean artery pressure in the AMBU bag and Hamilton transport ventilator groups. The investigators hypothesize that using the Hamilton transport ventilator will show a smaller change in P/F ratio, mean artery blood pressures and biventricular function compared to the AMBU bag group. If true, these findings would support using the Hamilton ventilator for transport in appropriate surgical patients. 2. To perform "in-vitro" flow analysis using a flow analyzer analyzer (CITREX H5: Buchs, Schweiz) and lung simulator (SmartLung 2000: Buchs, Schweiz) to measure the accuracy of the ventilations of Hamilton C1 ventilator and AMBU bag manual ventilation on different resistance and compliance settings of the lung simulator