Coughing, mucus accumulation, airway obstruction, and airway inflammation in control horses and horses affected with recurrent airway obstruction.
OBJECTIVE
To investigate relationships between cough frequency and mucus accumulation, airway obstruction, and airway inflammation and to determine effects of dexamethasone on coughing and mucus score.


METHODS
13 horses with recurrent airway obstruction (RAO) and 6 control horses.


METHODS
6 RAO-affected and 6 control horses were stabled for 3 days. Coughing was counted for 4 hours before and on each day horses were stabled. Before and on day 3 of stabling, tracheal mucus accumulation was scored, airway obstruction was assessed via maximal change in pleural pressure (deltaPpl(max)), and airway inflammation was evaluated by use of cytologic examination of bronchoalveolar lavage fluid (BALF). Effects of dexamethasone (0.1 mg/kg, IV, q 24 h for 7 days) were determined in 12 RAO-affected horses.


RESULTS
To assess frequency, coughing had to be counted for 1 hour. In RAO-affected horses, stabling was associated with increases in cough frequency, mucus score, and deltaPpl(max). Control horses coughed transiently when first stabled. In RAO-affected horses, coughing was correlated with deltaPpl(max), mucus score, and airway inflammation and was a sensitive and specific indicator of deltaPpl(max) > 6 cm H2O, mucus score > 1.0, and > 100 neutrophils/microL and > 20% neutrophils in BALF Dexamethasone reduced cough frequency, mucus score, and deltaPpl(max), but BALF neutrophil count remained increased.


CONCLUSIONS
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.
Robinson
N Edward
NE
Pulmonary Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA.
Berney
Cathy
C
Eberhart
Sue
S
deFeijter-Rupp
Heather L
HL
Jefcoat
Andrew M
AM
Cornelisse
Cornelis J
CJ
Gerber
Vincent M
VM
Derksen
Frederik J
FJ
D000402:Airway Obstruction / Q000150:complications* / Q000188:drug therapy / Q000473:pathology / Q000662:veterinary*; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000627:therapeutic use; D001992:Bronchoalveolar Lavage Fluid; D003371:Cough / Q000150:complications* / Q000473:pathology / Q000503:physiopathology; D003907:Dexamethasone / Q000627:therapeutic use; D006734:Horse Diseases / Q000188:drug therapy / Q000473:pathology* / Q000503:physiopathology*; D006736:Horses; D007249:Inflammation / Q000662:veterinary; D009093:Mucus / Q000502:physiology*; D012129:Respiratory Function Tests; D012137:Respiratory System / Q000473:pathology* / Q000503:physiopathology*; D013997:Time Factors
D000893:Anti-Inflammatory Agents; D003907:Dexamethasone