14Qp696 inHg hPa millibars barg ppO2 101Qp325 PaQfs millibar kbar kilopascals hydrostatic vapor PPO2 mb overpressure megapascals pQpsQpi oncotic fugacity systolic adiabatically temperature kilopascal pitot superpressure piezo ARMED 1013Qp25 trimix LMS100 atmospheric heliox Kp vapour Intraocular