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

Objective-To assess the validity of barometric whole-body plethysmography ( BWBP) as a means of monitoring airway responses to induced bronchoconstrict ion in healthy cats. Animals-8 healthy cats without history of bronchopulmonary disease or expos ure to indoor tobacco smoke. Procedure-Cats were placed into a barometric plethysmograph with an interna l volume of 38 L, and air flow was recorded at baseline and alter carbachol (concentrations 0.005, 0.01, 0.02, 0.05, 0.1, and 0.2%) was introduced int o 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 ti dal volume did not differ significantly from baseline values. Flow-derived measurements (pause, enhanced pause, and end-expiratory pause) increased si gnificantly 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 noninvasive. Airway reactivity was highly variable among cats and was not a function of baseline airway caliber, suggesting that ot her intrinsic mechanisms may be important.