ENDOTRACHEAL INTUBATION INFLUENCES RESPIRATORY WATER-LOSS DURING HEAT-STRESS IN YOUNG LAMBS

To study the effect of intubation on respiratory water loss (RWL) duri ng heat stress, 10 young nonsedated lambs were exposed to radiative he at stress both when intubated and when not. RWL, oxygen consumption (V O2), and carbon dioxide production were monitored continuously by usin g a flow-through system with a mass spectrometer for gas analysis. Whe n the lambs were not intubated, heat stress caused RWL to increase by 218%, whereas VO2 and body temperature remained unchanged. When the la mbs were intubated, heat stress caused RWL to increase by 131% and VO2 to increase by 36%. On extubation during heat stress, RWL increased b y 117 +/- 48% (standard error of the estimate) of the preextubation va lue and body temperature started to fall. This study shows that intuba tion reduces the ability of the lamb to increase RWL and heat loss dur ing heat stress in a warm environment, possibly as an effect of exclus ion of the nose and a reduction in dead space. After extubation, RWL i ncreases markedly, a finding that might also be valid for intubated in fants.