Y. Moens et al., DISTRIBUTION OF INSPIRED GAS TO EACH LUNG IN THE ANESTHETIZED HORSE AND INFLUENCE OF BODY SHAPE, Equine veterinary journal, 27(2), 1995, pp. 110-116
The distribution of inspired gas to each lung, time constants of the l
ungs and parameters of gas exchange were studied in 2 groups of horses
(mean bwt 606 kg), anaesthetised using thiopentone and chloral hydrat
e and breathing room air. One group (n=4) had a downward curved abdomi
nal contour (round-bellied) and the other group (n=4) had an upward cu
rved abdominal contour (flat-bellied). An equal distribution of inspir
ed gas between the lungs existed in both groups in dorsal recumbency.
Flat-bellied horses maintained this equal distribution in lateral recu
mbency whereas in round-bellied horses an uneven distribution of tidal
volume (V-T) developed. The percentage of (V-T) distributed to the de
pendent lung was 23% and 38% for left and right lateral recumbency res
pectively. The distribution of VT agreed with the ratio of time consta
nts of the lungs in flat-bellied horses but differed markedly from thi
s ratio in round-bellied horses suggesting that, in the latter, factor
s other than compliance and resistance play a role in distribution of
ventilation. Round bellied horses had a lower PaO2 and a larger (A-a)P
aO2 than flat-bellied horses in all body positions. The results are co
mpatible with the known hypothesis that pressure exerted by abdominal
contents on the dependent lung and diaphragm is an important factor in
ventilation/perfusion mismatch of the anaesthetised horse.