There are actually many ways we use flt phys. one is a simple calculation for O2 adjustment Barometric pressure at sending hospital times the FiO2 they are on divided by the barometric pressure at new altitude or (receiving facility in the case of pressurized aircraft transports).This will give you the new FiO2 needed to maintain status quo. It is also a good idea to adjust tidal volumes on ventilators to compensate for major altitude changes.
Mike
