Upper respiratory dead space in the chicken: Its fraction of the tidal volume

Abstract

1. 1. Tidal volume, vertical sternal displacement, and upper respiratory dead space volume were measured in the chicken and the point in the respiratory cycle at which fresh gas reaches the lung was determined. 2. 2. Respiratory dead space from the mediodorsal secondary bronchi to the mouth averaged 7.0 ml in chickens whose average body weight was 2.2 kg. 3. 3. Fresh gas did not reach the lung until 23% of the V T or 32% of the vertical sternal displacement had occurred. 4. 4. These findings indicate that upper respiratory dead space may be primarily responsible for delays between the beginning of inspiration and the onset of intrapulmonary CO 2 receptor discharges in birds.