THE PANTING RESPONSE OF NORMAL UNANESTHETIZED DOGS TO MEASURED DOSAGES OF DIATHERMY HEAT

Abstract

The changes in tidal vol., ventilation and respiratory rate of 5 normal trained unanesthetized dogs when heated by high frequency current were measured. These respiratory variables were measured by a body plethysmograph without masks and cannulae and with precautions to eliminate inertia. The diathermy heat dosage was equal to and twice the b.m.r. in an environment of 30-31[degree] and 50 [plus or minus] 10% relative humidity. Respiratory and ventilation rates increased before panting occurred but on the average there was no change in tidal vol. When panting commenced there was an abrupt increase in respiratory rate and a decrease in tidal vol. of 20-40% below the prepanting level. The respiration after the onset of panting was of 2 types which alternated. One type was characterized by a rapid respiratory rate of 200-350 per min. with a low tidal vol. This rapid breathing was produced mainly by thoracic movement during a state of inspiration maintained by the abdominal muscles. Such respiration is true panting. The other type of respiration occurred between panting intervals and consisted of a breathing superimposed on a state of abdominal expiration. The tidal vol. was higher and the respiratory rate less than the corresponding panting values. The slower respiration is maintained possibly for gaseous exchange while the rapid respiration aids in water evaporation without excessive loss of CO 2.