Summary We examined the effect of stabling on upper and lower airway inflammation in 14 yearling Arabian horses that had been at pasture since birth. Horses were divided into 2 groups of 7. One group was stabled for 3 months and the other remained at pasture. The groups were then switched over for another 3 months. The nasopharynx, guttural pouches and trachea were examined endoscopically and bronchoalveolar lavage performed every month. An upper airway inflammation score was devised based on the magnitude of pharyngeal lymphoid hyperplasia and guttural pouch inflammation. During stabling this score remained constant, whereas it decreased during the 3 months at pasture. Stabling was also associated with a higher number and percentage of neutrophils in bronchoalveolar lavage fluid and with a smaller percentage of lymphocytes. There was no correlation between upper airway inflammation score and bronchoalveolar lavage cytology. During a nasal occlusion test, dorsal displacement of the soft palate occurred more times in stabled than in pastured horses, but this was heavily biased by the results from one animal. We conclude that stabling is associated with inflammation of both the upper and lower airway of young horses.

Because of its sporadic nature, coughing cannot be assessed accurately by counting during brief periods. In RAO-affected horses, coughing is an indicator of airway inflammation and obstruction. Corticosteroid treatment reduces cough frequency concurrently with reductions in deltaPpl(max) and mucus accumulation in RAO-affected horses.

Summary During a trial to determine the dose response to the β2‐adrenergic agonist pirbuterol, we judged the severity of airway obstruction by use of a clinical scoring system and compared this to objective data obtained by quantitative measures of lung function. Six horses affected by recurrent airway obstruction were used in this trial. Four hundred and sixty‐eight measurements of lung function and clinical scores were obtained from 13 measurement periods when horses received each of 6 doses of pirbuterol. Scores of 1–4 were assigned to degree of nasal flaring and abdominal effort and summed for a total score. The veterinarian scoring the signs did not know the dose of pirbuterol received by the horse and was unaware of the lung function data. Nasal, abdominal and total scores were significantly related to changes in lung function and changes in breathing pattern. There were significant differences between total scores greater than 5 in indices that reflected changes in breathing strategy (peak inspiratory and expiratory flow), peripheral airway obstruction (dynamic elastance), and effort of breathing (maximal change in pleural pressure). Below a total score of 5, there were fewer significant differences in lung function even though measurements of pulmonary resistance and dynamic elastance indicated considerable airway obstruction. Failure of clinical score to reflect this low‐grade airway obstruction suggests that airway disease is underdiagnosed and its detection would be helped by the availability of a convenient lung function test.

FP (6 mg q12h) is as effective as DEX for prevention of acute exacerbations of RAO and lower doses should be evaluated. High-dose FP is not as effective as DEX for treatment of RAO exacerbations.

Summary The objective of the present study was to determine the effect of head and neck position on upper airway flow mechanics in exercising horses. Five Standardbred horses (452 ± 16.5 kg bwt; 4.7 ± 0.9 years [mean ± s.e.]) were exercised at 75% (Period A) and at 100% of maximal heart rate (Period B) with head and neck unrestrained, extended, or flexed. Airflow was measured using a facemask mounted pneumotachograph, while tracheal pressure during inhalation and exhalation (PUI and PUE) was measured using a nasotracheal catheter. With head and neck unrestrained, PUI, PUE, inspiratory and expiratory impedance (ZI, ZE), respiratory frequency (f) and indices describing the tidal breathing flow‐volume loops (TBFVLs) were similar to those previously reported. There were no significant changes in the extended position, except that expiratory time (Te) and ratio of peak expiratory flow and peak inspiratory flow (PEF/PIF) were significantly increased in Periods A and B, respectively. In contrast, in the flexed position, ZI was significantly increased in Period B. Also, inspiratory flow at 50% of tidal volume (IF50) was significantly decreased, and PEF/PIF and EF50/IF50 were significantly increased. At period A, PUI was increased and Te was prolonged. We conclude that during strenuous exercise head and neck extension has little effect on upper airway flow mechanics, but that head and neck flexion causes upper airway obstruction.