MEASUREMENT OF BRONCHODILATATION USING A SUPERFINE FIBEROPTIC BRONCHOSCOPE

In this study, we report the development and accuracy of a direct tech nique to measure airway calibre using a superfine fibreoptic bronchosc ope. Ten mongrel dogs were anaesthetized with pentobarbitone and the t rachea intubated with a tracheal tube; the small lumen of the tube all owed passage of a superfine fibreoptic bronchoscope (od 2.2 mm). Bronc hial cross-sectional area and airway pressure were recorded continuous ly and dynamic pulmonary compliance and airway resistance calculated. The dogs were allocated to one of two groups. In the first group (six dogs), bronchoconstriction was induced with histamine 10 mu g kg(-1) i .v. and 500 mu g kg(-1) h(-1) c.i.v. Thirty minutes later, adrenaline 0-0.4 mg kg(-1) was given i.v. Bronchial cross-sectional area, dynamic pulmonary compliance and airway resistance were assessed simultaneous ly. in the second group, 0.9% saline was given 30 min after placement of the superfine fibreoptic bronchoscope and 10 min later atropine 0.1 mu g kg(-1) was administered. In the first group, histamine decreased mean percentage bronchial cross-sectional area by 49.2 (SD 11.5) %, r educed dynamic pulmonary compliance from 32.1 (12.6) to 22.3 (5.2) mi cm H2O-1 and increased airway resistance from 39.1 (11.6) to 57.2 (10. 2) cm H2O litre(-1) s(-1). Adrenaline produced a dose-dependent increa se in percentage bronchial cross-sectional area and dynamic pulmonary compliance to 119.4 (37.3) % and 27.4 (5.5) mi cm H2O-1, respectively, and a decrease in airway resistance to 43.9 (7.2) cm H2O litre(-1) s( -1). There were significant correlations between percentage bronchial cross-sectional area and dynamic pulmonary compliance (r=0.720, P<0.00 01) and airway resistance (r=0.727, P<0.0001). Atropine 0.1 mg kg(-1) increased basal bronchial cross-sectional area to 137.5 (16.9) %. Thes e data indicate that adrenaline reversed histamine- and pentobarbitone -induced bronchoconstriction.