INVESTIGATION OF OPERATION OF AUTOMATIC RESPIRATORY VALVES
AIR FORCE SYSTEMS COMMAND WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB
Pagination or Media Count:
A new method and apparatus for determining the resistance and gas bypass of self-regulating respiratory valves is described. Bypass is defined as the amount of gas passing through the valve in the opposite direction during a respiratory cycle. The relationship between valve resistance and gas bypass has significance for oxygen-breathing apparatus, particularly with gravitational valves, in which too much bypass can conceivably lead to patients hyperkapnia. Gravitational, coil and gasproof valves were tested. In the study of the gravitational valve, coincidence of theoretical and experimental values for stationary flow and sinusoidal respiratory pulse flow was found. Closing of the valve in the idle phase depends on 3 factors 1 the vacuum required for drop of the valve, 2 valve inertia and friction, and 3 valve weight. For valves up to 3 g, the first factor proved decisive Greater valve weight at the same ventilation will result in less slippage. Coil valves and gasproof valves were found to act almost the same as the gravitational. Dependence of resistance on ventilation is a constant for gravitational valves but is a variable for coil valves. Absolute slippage values were about the same for all sizes of coil valves. Theoretical and experimental results agreed closely, and it was concluded that the slippage of a self-regulating valve of any kind can be approximately calculated if the geometric parameters and resistance to the operational conditions under study are known.
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