Airway reactivity measured by barometric whole-body plethysmography in healthy cats

Abstract

Objective - To assess the validity of barometric whole-body plethysmography (BWBP) as a means of monitoring airway responses to induced bronchocon-striction in healthy cats. Animals - 8 healthy cats without history of bronchopulmonary disease or exposure to indoor tobacco smoke. Procedure - Cats were placed into a barometric plethysmograph with an internal volume of 38 L, and air flow was recorded at baseline and after carbachol (concentrations 0.005, 0.01, 0.02, 0.05, 0.1, and 0.2%) was introduced into the chamber. A dose-response curve was generated for several flow-derived measurements, and airway reactivity was determined by interpolation of the dose-response curve for enhanced pause. Results - Peak inspiratory and expiratory flows increased significantly, but respiratory rate, inspiratory and expiratory times, relaxation time, and tidal volume did not differ significantly from baseline values. Flow-derived measurements (pause, enhanced pause, and end-expiratory pause) increased significantly at carbachol concentrations > 0.02%. Baseline measurements did not correlate with indices of airway reactivity. Conclusions and Clinical Relevance - Airway reactivity can be measured by use of BWBP, which is non-invasive. Airway reactivity was highly variable among cats and was not a function of baseline airway caliber, suggesting that other intrinsic mechanisms may be important. (Am J Vet Res 1999;60:1487-1492).