Positive pressure generation by pneumatic and electronic O2 regulators: a bench experimental evaluation.
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.


OBJECTIVE
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 approximately 25% (p < 0.05) and by approximately 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.
Beaumont
M
M
Institut de Médecine Aérospatiale du Service de Santé des Armées, Brétigny-sur-Orge, France.
Lejeune
D
D
Isabey
D
D
Marotte
H
H
Harf
A
A
Lofaso
F
F
D000337:Aerospace Medicine; D000388:Air; D004581:Electronics; D004867:Equipment Design; D005676:Gravity Suits; D006801:Humans; D008348:Manikins; D008397:Masks; D008889:Military Personnel; D010102:Oxygen Inhalation Therapy / Q000295:instrumentation*; D011175:Positive-Pressure Respiration / Q000295:instrumentation*; D011312:Pressure; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D014939:Work of Breathing