Effects of graded resistance to tracheal air flow in man.

Abstract

Experiments were made on 11 human subjects to determine the effects of four levels of air flow resistance when added independently or simultaneously to inspiration and expiration. Resistance ranged from 0.10 to 0.43 mm H2O/cc/sec. a) The primary effect of resistance to air flow is a reduction in air flow velocity and an increase in duration of the impeded phase; b) resistance on one phase may alter the pattern of air flow of the other phase as well. This alteration is generally an elevated maximal flow velocity; c) reduction in respiratory frequency, increase in tidal volume and increase in expiratory reserve, usually exhibited by individuals breathing in and out through resistance, are mainly associated with the impedance of expiratory flow; d) the extra work associated with breathing through the spectrum of resistances studied increases in a linear fashion; e) as a result of air flow impedance, pulmonary ventilation is reduced and alveolar carbon dioxide rises and oxygen tension falls. Levels of resistance used have only a slight respiratory effect when subjects are at rest but bring about dramatic changes in alveolar gas composition when ventilatory demands are increased by moderate exercise. Submitted on October 18, 1956