Effective resistance of the respiratory system studied by a quick release technique.
A human subject with mouthpiece in place makes inspiratory or expiratory effort against a closed shutter which abruptly opens when a predetermined pressure (PO) is developed. Pressure at the mouth (Pao) and flow (V) are continuously recorded. When the shutter opens, Pao changes toward atmospheric - first abruptly and then gradually, while V rapidly rises to a peak value (Vpeak) and then gradually declines. In any series of trials PO is held constant, but resistance external to the subject (Rext) is changed with each trial. In different series PO is varied. In any series of trials at constant PO the relationship between Pao and V was linear. The slope (K) of the straight line fitted to the experimental points was interpreted as being equal in magnitude to the 'effective resistance' (Reff) of the respiratory system. Reff has two components - a true resistance (Rint) and a virtual one (Rfv) related to the force-velocity characteristic of the respiratory muscles. On the assumption that Rint is independent of PO but that Rfv varies linearly with it, Rint and Rfv can be evaluated.
D000403:Airway Resistance; D001696:Biomechanical Phenomena; D004947:Esophagus / Q000502:physiology; D006801:Humans; D008433:Mathematics; D010827:Physiology / Q000295:instrumentation / Q000379:methods*; D011312:Pressure; D012119:Respiration