Effects of using long breathing hoses upon mask pressure

Area of Science:

• Aviation Physiology
• Aerospace Medicine

Background:

• Rapid decompression in aircraft can lead to dangerous mask pressures.
• Oxygen breathing hose length and mask fit are critical factors in managing pressure.

Purpose of the Study:

• To determine the effects of oxygen breathing hose length and mask fit on mask pressure during simulated aircraft decompressions.
• To identify safe limits for hose length and decompression rates to prevent pulmonary damage.

Main Methods:

• Simulated decompressions from 2,438 m to higher altitudes (6,096–15,240 m) using oxygen hoses of varying lengths (0.9–8.2 m).
• Measured peak mask pressures and duration of high pressure under different conditions.
• Analyzed factors influencing mask pressure, including mask fit, hose compliance, and decompression rate.

Main Results:

• Mask pressure increased significantly with longer hose lengths.
• Peak mask pressures frequently exceeded 80 mm Hg, a level associated with pulmonary damage.
• Larger aircraft cabins mitigated high mask pressures due to slower decompression rates.

Conclusions:

• Long breathing hoses should be avoided in smaller aircraft due to rapid decompression rates and high mask pressures.
• Oxygen should be used with hoses longer than 2.9 m above 2,438 m to prevent hypoxia.
• Safe decompression rates are provided to maintain mask pressures below 80 mm Hg.