Respiratory and circulatory responses of hyperthermic chickens

Abstract

Body temperature, respiratory rate, minute volume, heart rate and blood pressure were determined in both sexes of White Leghorn Chickens exposed at 40.5° C. Respiratory responses and heart rate increased with increasing body temperature and then invariably declined before the final temperature. Inflection in respiratory rate occurred at 43.5-44.5° c. (average max. 140-170 breaths/min.). Minute volume inflection occurred at 44.5-45.5° c. (average max. 2300 ml. for males and 1700 ml. for females). Minute volume was maintained at the higher body temperature by an increase in tidal volume. Decline in heart rate occurred at body temperatures in excess of 46° c. Blood pressure either remained unchanged (males) or declined slowly (females) until a body temperature of 45° c. for diastolic and 46° c. for systolic. Above these temperatures a precipitous decline ensued. Thus, the body temperatures at which changes occurred were different for the various responses, and there were some differences in response between sexes during hypertherinia.