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Publication Abstracts

Positive Pressure Generation by Pneumatic and Electronic O2 Regulators: A Bench Experimental Evaluation

Maurice Beaumont, M.D., Ph.D., Damien Lejeune, M.D., D. Isabey, Ph.D., Henri Marotte, M.D., Ph.D., Alain Harf, M.D., Ph.D., and Frédéric Lofaso, M.D., Ph.D.
Aviat Space Environ Med 1999; 70:812-6

Abstract

Background: The introduction of advanced anti-G protection into agile fast fighter aircraft may result in the regular use of positive pressure breathing (PPB) for G protection by aircrew. Since PPB results in an external additional work of breathing (WoB), we compared the mechanical performance of the pneumatic and electronic O2 regulators designed for "Mirage 2000" and "Rafale" aircraft. Hypothesis: Since mask pressure is regulated by the electronic device in relation to flow, mask pressure will remain constant throughout the respiratory cycle, so that PPB-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 (DeltaP) and calculated WoB at 0, 3 and 6 kPa of PPB (0, 30 and 60 cm H2O, respectively), 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 device, inspiratory and expiratory WoB with the electronic device were respectively lower by ~25% (p < 0.05) and by ~10% (NS) at 3 and 6 kPa of PPB, for all respiratory conditions. Nevertheless, we also observed remaining variations in mask pressure with the electronic regulator, due to complex impedance of the inspiratory circuit, since the device uses the pressure measured into the regulator. Conclusions: We concluded that the electronic control of mask pressure is relatively efficient but that the device would be improved by placing the site of the pressure measurement into the mask.

Keywords: +Gz tolerance, positive pressure breathing, work of breathing.

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Table of Contents for Volume 70, Number 8 of the ASME journal.