Relation of Increased Airway Resistance to Breathing Work and Breath Velocity and Acceleration Patterns With Maximum and Near Maximum Breathing Effort

Abstract

The oxygen cost of breathing, mechanical work done in breathing, efficiency of breathing and breath patterns have been studied at various resistance levels with maximum breathing effort. With the chest-lung complex considered as a machine for doing external work, it was observed that mechanical efficiencies increased with increasing airway resistance, to a point, after which they fell off. When the oxygen cost was corrected for work done on the chest-lung complex, efficiencies were observed to decrease with increasing airway resistance. Breath acceleration patterns were observed to provide a more sensitive appraisal of changes in the movement of the breath than either breath volume or velocity patterns. External work output increased with increasing external resistance only to a point, after which it decreased. At low resistance levels, work output was contraction speed limited and at high resistance levels it was contraction force limited. With maximum effort at all resistance levels oxygen consumption appeared to be constant. Data are also presented as peak alveolar pressure, breath velocity and change in functional residual capacity. Inspiratory breath phase percentage increased to more than half the cycle length with increasing airway resistance. Submitted on March 18, 1958