Objective—To evaluate effects of sedation on stability
of resistance of the respiratory system (RRS) and
measures of resting energy expenditure (REE) by use
of open-flow indirect calorimetry (IC) and treatment
with aerosolized albuterol on REE in horses with
recurrent airway obstruction (RAO).
Animals—9 clinically normal horses and 8 horses
Procedure—In phase 1, RRS was measured by using
forced oscillometry (FOT) in 5 clinically normal horses
before and after sedation with xylazine. In phase 2,
REE was measured in 4 clinically normal horses
between 20 and 25 minutes and again 35 to 40 minutes
after sedation with xylazine. In phase 3, IC was
performed between 20 and 25 minutes and FOT was
performed between 30 and 35 minutes after xylazine
administration in 8 horses with RAO; after administration
of 450 µg of albuterol, IC and FOT were repeated.
Results—In phase 1, RRS values were significantly
lower 5 and 10 minutes after sedation. In phase 2,
diminishing sedation did not significantly affect REE.
In phase 3, there was a significant decrease in mean
RRS (1.15 ± 0.25 vs 0.84 ± 0.14 cm H20/L/s) and REE
(30.68 ± 17.89 vs 27.46 ± 16.54 kcal/kg/d) after
Conclusions and Clinical Relevance—FOT and IC
are useful in obtaining repeatable measurements of
RRS and REE, respectively, in sedated horses.
Concurrent bronchodilation and decreased REE after
albuterol administration suggest that increased work
of breathing as a result of airway obstruction may
contribute to increased energy demands in horses
with RAO. (Am J Vet Res2003;64:235–242)