Positive pressure generation by pneumatic and electronic O-2 regulators: Abench experimental evaluation

Background: The introduction of advanced anti-C protection into agile fast fighter aircraft may result in the regular use of positive pressure breathi ng (PPB) for G protection by aircrew. Since PPB results in an external addi tional work of breathing (WoB), we compared the mechanical performance of t he pneumatic and electronic O-2 regulators designed for "Mirage 2000" and " Rafale" aircraft. Hypothesis: Since mask pressure is regulated by the elect ronic device in relation to flow, mask pressure will remain constant throug hout the respiratory cycle, so that PPE-related additional WoB will be less with the electronic regulator. Methods: In a bench dynamic study performed with a sinusoidal pump, we measured variations in mask pressure (Delta P) and calculated WoB at 0, 3 and 6 kPa of PPB (0, 30 and 60 cm H2O, respectiv ely), for 0.5, 1 and 2 L of volume and for 10, 15 and 20 cycles per minute of respiratory rate. Results: We found that, compared with the pneumatic de vice, inspiratory and expiratory WoB with the electronic device were respec tively lower by similar to 25% (p < 0.05) and by similar to 10% (NS) at 3 a nd 6 kPa of PPB, for all respiratory conditions. Nevertheless, we also obse rved remaining variations in mask pressure with the electronic regulator, d ue to complex impedance of the inspiratory circuit, since the device uses t he pressure measured into the regulator. Conclusions We concluded that the electronic control of mask pressure is relatively efficient but that the de vice would be improved by placing the site of the pressure measurement into the mask.