Alveolar clearance in horses with chronic obstructive pulmonary disease

Objective-To assess sensitivity! of scintigraphic alveolar clearance rate a s an indicator of alveolar epithelium damage in horses. Animals-5 healthy horses (group A) and 5 with chronic obstructive pulmonary disease (COPD; group B). Procedure-Horses underwent clearance rate (k [%/min]) determination. Cleara nce rate of group-B horses was determined after remission of the disease fo llowing 2 months at pasture (remission 1), stabling in a controlled environ ment (remission 2), and during crisis induced by exposure to moldy hay and straw. Methacholine challenge test was performed at each investigation peri od to determine nonspecific pulmonary airway hyperresponsiveness. Pulmonary function tests (PFT) also were performed, and cell populations in bronchoa lveolar lavage (BAL) fluid were determined on another occasion. Results-Group-B horses had significantly faster mean clearance rate during crisis (k = 4.30 +/- 0.95%/min), compared with that for remission 1 (k = 1. 98 +/- 0.55 %/min), which did not differ from the rate in group-A horses (k = 1.95 +/- 0.33%/min). Despite lack of clinical signs of COPD during remis sion when stabled in a controlled environment, an intermediate value was fo und (k = 3.20 +/- 0.72%/min). Conclusions-This technique allowed grading of lung damage induced by COPD, whereas use of PFT and determination of BAL fluid cell populations failed t o differentiate between remission 1 and remission 2. Clinical Relevance-Determination of alveolar clearance rate by use of scint igraphy is a sensitive indicator of lung damage. A modified clearance rate was found despite the lack of clinical and functional changes.