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Abstract

Objective—To examine the effects of an aerosolized β2-adrenoreceptor agonist, albuterol, on performance during a standardized incremental exercise test in clinically normal horses.

Animals—8 Standardbred pacing mares.

Procedure—Clinically normal horses, as judged by use of physical examination, hematologic findings, serum biochemical analysis, and airway endoscopy, were randomly assigned to 2 groups and were given 900 µg of albuterol via a metered-dose inhaler 30 minutes before beginning a standardized incremental exercise test in a crossover design with a 7-day minimum washout. Further examination included measurement of baseline lung mechanics, response to histamine bronchoprovocation, and bronchoalveolar lavage.

Results—No significant differences (albuterol vs placebo) were seen for any incremental exercise test variables (ie, maximum oxygen consumption, maximum carbon dioxide consumption, respiratory quotient, treadmill speed at heart rate of 200 beats/min, or number of steps completed during an incremental exercise protocol). Mast cell percentage was significantly (r = –0.84) associated with the concentration of aerosolized histamine that evoked a 100% increase in total respiratory system resistance. No other direct correlations between bronchoalveolar lavage fluid cell types and any indices of exercise capacity or airway reactivity were found.

Conclusions and Clinical Relevance—Although no horse had exercise intolerance, 4 horses had airway hyperreactivity with bronchoalveolar lavage fluid mastocytosis; these horses may have been subclinically affected with inflammatory airway disease. In our study, albuterol did not enhance performance in 8 clinically normal racing-fit Standardbreds. (Am J Vet Res 2001;62:1812–1817)

Full access
in American Journal of Veterinary Research

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)

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in American Journal of Veterinary Research

Abstract

Objective—To validate the use of noninvasive pulmonary function testing in sedated and nonsedated llamas and establish reference range parameters of respiratory mechanical function.

Animals—10 healthy adult llamas.

Procedures—Pulmonary function testing in llamas included the following: measurement of functional residual capacity (FRC) via helium dilution, respiratory inductance plethysmography (RIP) to assess breathing pattern and flow limitations, esophageal-balloon pneumotachography, and a monofrequency forced oscillatory technique (FOT; 1 to 7 Hz) before and after IM administration of xylazine (0.2 mg/kg).

Results—The following mean ± SD measurements of respiratory function were obtained in nonsedated llamas: FRC (5.60 ± 1.24 L), tidal volume (1.03 ± 0.3 L), dynamic compliance (0.83 ± 0.4 L/cm H2O), pulmonary resistance (RL; 1.42 ± 0.54 cm H2O/L/s), and respiratory system resistance (2.4 ± 0.9, 2.3 ± 0.7, 2.2 ± 0.6, 2.7 ± 0.7, and 2.5 ± 0.5 cm H2O/L/s at 1, 2, 3, 5, and 7 Hz, respectively) by use of FOT. Measurements of flow limitations via RIP were comparable to other species. Sedation with xylazine induced significant increases in RL and maximum change in transpulmonary pressure. Following sedation, a mean 127% increase in RL and mean 116% increase in respiratory system resistance were observed across 1 to 7 Hz. The magnitude of change in respiratory system resistance increased with decreasing impulse frequency, suggesting bronchoconstriction.

Conclusions and Clinical Relevance—Noninvasive pulmonary function testing is well tolerated in untrained unsedated llamas. These techniques have clinical applications in the diagnosis and treatment of respiratory tract disease, although testing should not be performed after sedation with xylazine.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate respiratory mechanical function and bronchoalveolar lavage (BAL) cytologic results in healthy alpacas.

Animals—16 client-owned adult alpacas.

Procedures—Measurements of pulmonary function were performed, including functional residual capacity (FRC) via helium dilution, respiratory system resistance via forced oscillatory technique (FOT), and assessment of breathing pattern by use of respiratory inductive plethysmography (RIP) in standing and sternally recumbent alpacas. Bronchoalveolar lavage was performed orotracheally during short-term anesthesia.

Results—Mean ± SD measurements of respiratory function were obtained in standing alpacas for FRC (3.19 ± 0.53 L), tidal volume (0.8 ± 0.13 L), and respiratory system resistance at 1 Hz (2.70 ± 0.88 cm H2O/L/s), 2 Hz (2.98 ± 0.70 cm H2O/L/s), 3 Hz (3.14 ± 0.77 cm H2O/L/s), 5 Hz (3.45 ± 0.91 cm H2O/L/s), and 7 Hz (3.84 ± 0.93 cm H2O/L/s). Mean phase angle, as a measurement of thoracoabdominal asynchrony, was 19.59 ± 10.06°, and mean difference between nasal and plethysmographic flow measurements was 0.18 ± 0.07 L/s. Tidal volume, peak inspiratory flow, and peak expiratory flow were significantly higher in sternally recumbent alpacas than in standing alpacas. Cytologic examination of BAL fluid revealed 58.52 ± 12.36% alveolar macrophages, 30.53 ± 13.78% lymphocytes, 10.95 ± 9.29% neutrophils, 0% mast cells, and several ciliated epithelial cells.

Conclusions and Clinical Relevance—Pulmonary function testing was tolerated well in nonsedated untrained alpacas. Bronchoalveolar lavage in alpacas yielded samples with adequate cellularity that had a greater abundance of neutrophils than has been reported in horses.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the use of a modified whole body plethysmograph in awake sheep.

Animals—10 healthy adult sheep.

Procedure—Concurrent measurements of specific airway resistance (sRaw) and pulmonary resistance (RL) were obtained using a novel noninvasive headout constant-volume plethysmograph and esophageal balloon-pneumotachography, respectively. All data were collected before and after external resistive loading with 1 and 5.6 cm H20/L/s. Functional residual capacity (FRC) was measured by helium dilution for computation of airway resistance (Raw) preloading (Raw = sRaw/FRC).

Results—The sRaw and RL were closely correlated in 10 adult sheep. Additionally, sRaw and RL accurately reflected the magnitude of added resistance. The mean FRC was 52 mL/kg and used to calculate Raw. At baseline, the values for Raw were significantly correlated with sRaw and RL.

Conclusions and Clinical Relevance—Precise measurements of sRaw and Raw at baseline and sRaw after external resistive loading were obtained by use of this novel noninvasive plethysmographic technology. This method should have application to veterinary patients or animals used in research in which noninvasive rapid or serial measurements of sRaw in the conscious state are required. (Am J Vet Res 2004;65:1259–1264)

Full access
in American Journal of Veterinary Research