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Effect of aerosolized albuterol sulfate on resting energy expenditure determined by use of open-flow indirect calorimetry in horses with recurrent airway obstruction

Melissa R. MazanLung Function Laboratory, Department of Clinical Sciences, School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

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Andrew M. HoffmanLung Function Laboratory, Department of Clinical Sciences, School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

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Heike KuehnLung Function Laboratory, Department of Clinical Sciences, School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

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Edward F. DeveneyPhysics Department, School of Arts and Sciences, Bridgewater State College, Bridgewater, MA 02325.

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Abstract

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 with RAO.

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 albuterol administration.

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)

Abstract

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 with RAO.

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 albuterol administration.

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)