IRREGULAR BREATHING IN YOUNG LAMBS AND NEWBORN-INFANTS DURING HEAT-STRESS

Ten healthy unanaesthetized full-term lambs, aged 4-12 days, were stud ied during moderate radiant heat stress, and 21 full-term newborn infa nts were studied during moderate convective heat stress. The rate of b reathing and the breathing pattern were recorded, using strain gauges made of mercury-filled rubber tubing placed around the thorax and abdo men. In both the lambs and the infants the respiratory rate increased during heat stress. When this increase began, both the lambs and infan ts had short periods of very rapid breathing followed by short apnoeas . The concentrations of carbon dioxide and water in a flow-through sys tem collecting expired air increased during the short periods of rapid breathing and then decreased ag;ain during the subsequent short apnoe ic period.