VENTILATION, GASEOUS EXCHANGE AND AIR SAC GASES DURING MODERATE THERMAL PANTING IN DOMESTIC FOWL

¹ Department of Veterinary Physiology, University of Edinburgh, Edinburgh EH9 1QH
² Department of Biology, University of Salford, Salford M5 4WT

Gaseous exchange, ventilatory pattern and gas levels within the interclavicular and abdominal air sacs of domestic fowl were monitored before, during and after periods of moderate hyperthermic panting. O₂ consumption (V_O2) remained virtually unaltered and CO₂ production (V_CO2) increased slightly during panting as compared to normal respiration. Resting V_O2 was 12·2 ml.kg^-1.min^-1. Resting (eupneic) P_O2 and P_CO2 of the interclavicular and abdominal air sacs were 100·1 and 38·5 torr, and 125·2 and 16·4 torr respectively. During panting the partial pressure of the abdominal air sac P_{abs, O2} and P_{abs, CO2} fell and rose to extreme values of 109 and 29·8 torr respectively. Simultaneously the partial pressure of the interclavicular air sac P_{ics, O2} and P_{ics, CO2} changed by smaller amounts to 107·5 and 32·3 torr respectively. Ventilatory pattern during thermal panting was characterized by rapid, shallow movements which were interrupted at regular intervals by short sequences of slower, deeper breaths. During these intermittent periods of eupneic breathing gas levels returned towards normal and these alterations were reflected in transient variations in V_O2 and V_CO2 about their mean values. Changes in gas levels within the lung-air sac system are discussed in connexion with the peripheral control of ventilation during panting.