THE EFFECT OF TEMPERATURE AND HYPOXIA HYPERCAPNIA ON THE RESPIRATORY PATTERN OF THE UNRESTRAINED LIZARD, POGONA VITTICEPS

The effect of altering body temperature and the oxygen and carbon diox ide composition of inspired air on the respiratory pattern of the unre strained lizard Pogona vitticeps was determined using pneumotachometry that did not require restraining the animal. P. vitticeps demonstrate d a typical reptilian breathing pattern of groups of breaths separated by periods of breath-holding. Respiratory patterns were measured at 1 8 degrees C and at 37 degrees C. Minute ventilation decreased at the l ower temperature as a result of a decrease in average frequency. Tidal volume was temperature independent. The change in average frequency r esulted from both a decrease in the instantaneous inspiratory time and an increase in the time spent in a non-ventilatory period. As a resul t, the work of breathing was less at 18 degrees C than at 37 degrees C . With the exception of tidal volume, breathing patterns were independ ent of changes to the composition of inspired air. At both 18 degrees C and 37 degrees C, inspiring a 5% CO2/13% O-2/82% N-2 gas mixture inc reased tidal volume but did not increase minute ventilation.