Ventilatory chemosensitivity in the chick embryo.

In the externally pipped chicken embryo, oxygen consumption through the chorioallantoic membrane (VO2CAM) ranged between 2 and 55% (mean approximately 24%) of that through the lungs (VO2lung). Hypercapnia (5'-10' of 2, 5, or 8% CO2) or mild hypoxia (15% O2) had minor effects on VO2, whereas moderate or severe hypoxia (10-5% O2) caused large drops of VO2. Hypoxia or hypercapnia delivered through the lungs increased pulmonary ventilation (VE), largely through increases in tidal volume (VT).

Effects of posture on the respiratory mechanics of the chick embryo.

In the chicken embryo, pulmonary ventilation and pulmonary gas exchange begin approximately one day before the completion of hatching. We asked to what extent the posture inside the egg, and the presence of the eggshell and membranes, may alter the mechanical behaviour of the respiratory system. The passive mechanical properties of the respiratory system were studied in chicken embryos during the internal pipping phase (rupture of the air cell) or the external pipping phase (hole in the eggshell).

Metabolic control of pulmonary ventilation in the developing chick embryo.

In birds, during the period from the breaking of the air cell by the beak (internal pipping) to hatching, pulmonary ventilation (VE) begins and gas exchange is jointly provided by the lungs and the chorioallantoic membrane (CAM). We asked to what extent, during this phase of two concurrent gas exchange organs, changes in the embryo's metabolic needs were accompanied by changes in VE. The carbon dioxide and oxygen exchange rates (VCO2, VO2) through lungs and CAM were separately, but simultaneously, measured in chicken embryos at 20-21 days of incubation, while VE was calculated from the measurements of pressure oscillations in the air cell during breathing.