MEASUREMENT OF BRONCHOCONSTRICTION USING WHOLE-BODY PLETHYSMOGRAPH - COMPARISON OF FREELY MOVING VERSUS RESTRAINED GUINEA-PIGS

We have previously measured pulmonary function in guinea pigs using a double-chambered plethysmograph, however, the question remains regardi ng the accuracy of the double-chamber to gauge the long-term pulmonary function of late asthmatic response. This may be affected by confound ing factors, such as stress on the animal and differences in size of t he collar around the neck. Therefore, in this study we compared histam ine-induced bronchoconstriction in the same guinea pigs using a single - versus a double-chambered body box. In the double-chambered body box , the specific airway resistance is proportional to time delay between thoracic and nasal flows and measured in cmH(2)P.s. Whereas, in the s ingle-chambered body box, PenH units (Enhanced Pause) reflect ''effort of breathing.'' This is measured as the pause between inspiration and expiration. Doubling concentrations of histamine (12.5-200 mu g/ml di ssolved in normal saline) were administered by DeVilbiss nebulizer for 1 min, followed by 1 min suction of residual drug in the chamber, and then the airway resistance was recorded by the computer for the follo wing 3 min. There was a 15-min wash-out period between two doses of hi stamine. There was no statistically significant difference (F > 0.05) in the PC,,, values for histamine between the two methods, however, it was much easier to work with the single-chambered body box in terms o f handling the animal and eliminating the possible influence of collar placement on the bronchoconstriction. In conclusion, the data suggest s histamine challenges produce equivalent PC,,, data in both the doubl e-chambered plethysmograph with sRAW units and single-chambered plethy smograph using the PenH units. (C) 1998 Elsevier Science Inc.