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

Area of Science:

• Aerospace Medicine
• Respiratory Physiology
• Biomedical Engineering

Background:

• Advanced anti-G protection in fighter aircraft necessitates positive pressure breathing (PPB).
• Positive pressure breathing (PPB) increases the work of breathing (WoB) for aircrew.
• This study compares pneumatic and electronic O2 regulators for PPB in fighter aircraft.

Purpose of the Study:

• To evaluate the mechanical performance of pneumatic and electronic O2 regulators during PPB.
• To determine if electronic regulators reduce the additional work of breathing (WoB) associated with PPB.
• To compare mask pressure regulation between pneumatic and electronic systems.

Main Methods:

• A dynamic bench study using a sinusoidal pump.
• Measurement of mask pressure variations (deltaP) under varying PPB levels (0-6 kPa).
• Calculation of work of breathing (WoB) at different volumes (0.5-2 L) and respiratory rates (10-20 cycles/min).

Main Results:

• Electronic regulators reduced inspiratory WoB by ~25% (p < 0.05) and expiratory WoB by ~10% compared to pneumatic regulators at 3 and 6 kPa PPB.
• These improvements were observed across all tested respiratory conditions.
• Mask pressure variations persisted with the electronic regulator due to circuit impedance and sensor location.

Conclusions:

• Electronic control of mask pressure during PPB is effective but not optimal.
• Relocating the pressure sensor to the mask would enhance electronic regulator performance.
• Optimized regulators can improve aircrew comfort and safety during high-G maneuvers.