Abstract: The gas sample line in a cardlopulmonary performance analyzing system is designed to include a flow sensor for measuring the rate of flow of the gas sample being drawn and is used to adjust the initial transit time value measured at the time of system calibration for a known value of flow in arriving at a new or current transit time value at the time that a test is actually being performed on a patient. This dynamically compensates the transit time for variations in the sample flow rate, thus providing a system with accuracy that is not dependent upon maintaining constant sample flow rates.