Influence of subclinical inflammatory airway disease on equine respiratory function evaluated by impulse oscillometry.
BACKGROUND
Inflammatory airway disease (IAD) is a nonseptic condition of the lower respiratory tract. Its negative impact on respiratory function has previously been described using either forced expiration or forced oscillations techniques. However, sedation or drug-induced bronchoconstriction were usually required. The impulse oscillometry system (IOS) is a noninvasive and sensitive respiratory function test validated in horses, which could be useful to evaluate IAD-affected horses without further procedures.


OBJECTIVE
To determine the sensitivity of IOS in detecting alterations of the respiratory function in subclinically IAD-affected horses without inducing bronchoprovocation and to characterise their respiratory impedance according to frequency for each respiratory phase.


METHODS
Pulmonary function was evaluated at rest by IOS in 34 Standardbred trotters. According to the cytology of bronchoalveolar lavage fluid (BALF), 19 horses were defined as IAD-affected and 15 horses were used as control (CTL). Total respiratory resistance (Rrs) and reactance (Xrs) from 1-20 Hz as well as their inspiratory and expiratory components were compared between groups.


RESULTS
A significant increase of Rrs at the lower frequencies (R1-10 Hz) as well as a significant decrease of Xrs beyond 5 Hz (X5-20 Hz) was observed in IAD compared to CTL horses. IOS-data was also significantly different between inspiration and expiration in IAD-affected horses. In the whole population, both BALF eosinophil and mast cell counts were significantly correlated with IOS measurements.


CONCLUSIONS
Functional respiratory impairment may be measured, even in the absence of clinical signs of disease. In IAD-affected horses, the different parameters of respiratory function (Rrs or Xrs) may vary depending on the inflammatory cell profiles represented in BALF.


CONCLUSIONS
Impulse oscillometry could be used in a routine clinical setting as a noninvasive method for early detection of subclinical respiratory disease and of the results of treatment in horses.
Richard
E A
EA
Department of Physiology, Faculty of Veterinary Medicine, Bat. B42, University of Liège, 20 Boulevard de Colonster, 4000 Liège, Belgium.
Fortier
G D
GD
Denoix
J-M
JM
Art
T
T
Lekeux
P M
PM
Van Erck
E
E
D000818:Animals; D001992:Bronchoalveolar Lavage Fluid; D006734:Horse Diseases / Q000175:diagnosis*; D006736:Horses; D007249:Inflammation / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D009991:Oscillometry / Q000379:methods / Q000662:veterinary*; D012140:Respiratory Tract Diseases / Q000175:diagnosis / Q000662:veterinary*