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
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
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)
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.
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.
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)