An analysis on the mechanism responsible for genesis of deformation of expiratory-gas-concentration curves in chickens.

Phenomena associated with a deformation of short-time occurrence and noticed on concentration curves of tidal O2 and CO2 were examined in adult hens sitting quietly in a cage or suspended in prone position. During the episode of deformation, a decrease in arterial oxygen-gas tension was apparent. It was associated with a slight increase in arterial carbon-dioxide-gas tension and a slight acidic shift of arterial blood pH. The episode was associated with increases in intrapressure of the interclavicular and bilateral abdominal air sacs. The tracheal expiratory-gas flow changed in pattern. Hypoventilation due to reduction in tidal volume or respiratory rate could not be detected during the episode. The episode was suddenly terminated at the hen's body movement induced spontaneously or by pinching the comb, at coughlike activity or at no obvious change in behavior in a quietly resting position. Deformation similar to the spontaneous one could be induced by 3 ml-water flushing into the trachea or 0.1% methacholine aerosol inhalation. The mechanism responsible for the genesis of deformation was discussed. It was presumed to be based upon some mechanism, such as mucous accumulation in the lung, rather than upon the pulmonary smooth-muscle contraction.