Intrapressures and oxygen contents of air sacs at deformation of expiratory-oxygen-concentration curve in chickens.

Intrapressures and oxygen contents of air sacs were measured in adult hens showing spontaneous deformation episodes of expiratory oxygen curve. Differential pressures between air sacs were also determined. The deformation resembled that seen at the time of uneven pulmonary ventilation in mammals. To analyse the mechanism responsible for genesis of the deformation episode, an airway was obstructed in the unilateral extrapulmonary primary bronchus by a small balloon. This maneuver caused the expiratory oxygen curve to deform and values of intrapressure and oxygen content of air sacs to change similarly to those of the spontaneous deformation episode. Some of the latter changes in intrapressure and oxygen content caused by obstruction in the left bronchus were different from those caused by obstruction in the right one. The side of airway obstruction at the spontaneous deformation episode could thus be deduced by this result. It was hypothesized that respiratory air from the lung-air sac system on the obstructed side might have flowed through the clavicular air sac to the primary bronchus on the non-obstructed side and vice versa. This condition might induce large respiratory fluctuations of oxygen content in the clavicular air sac, and would be responsible for plateau inclination (deformation) of the expiratory oxygen curve.