Viscosity correction for breathing gas mixtures measured via a laminar flow element

To minimize previously observed inaccuracies in the measurement of the flow rates of breathing gas mixtures, errors in the measurement of the pressure differential across the LFE with short diffusers using high frequency response pressure transducers were ruled out. A Laminar Flow Element was calibrated with air, nitrogen, and helium at various pressure and temperature conditions. The feasibility of using the Universal Calibration Curve determined from atmospheric air data to estimate the flow rate of other gases at hyperbaric conditions was evaluated. The viscosity values of pure gases calculated by theoretical methods were compared to the viscosity values estimated by using the Universal Calibration Curve Viscosity Iteration method. Using flowrate calibration data for the gas mixtures of interest, the viscosity values for these gas mixtures were estimated. These viscosity values were then compared to the corresponding viscosity values calculated by theoretical methods. The Universal Calibration Curve obtained by fitting flowrate calibration data of air flowing at STP can be used to estimate the flow of other gases flowing at hyperbaric pressures.