Vascular involvement in exercise-induced airway narrowing in patients with bronchial asthma

The bronchial microcirculation has the potential to contribute to the pathophysiologic mechanisms of exercise-induced bronchoconstriction (EIB) in asthmatic patients. This study was designed to determine whether increase in airway vascular permeability is associated with the severity of EIB in asthmatic patients.

Cross-sectional analysis.

University hospital.

Twenty-five asthmatic patients and 12 normal control subjects.

All asthmatics performed an exercise test, and the percentage of maximal fall in FEV(1) and the area under the curve of the percentage fall in FEV(1) plotted against time for 30 min (AUC(0-30)) were determined.

The inflammatory indexes, NO levels, and airway vascular permeability index (ratio of albumin concentrations in induced sputum and serum) were examined in all subjects. The airway vascular permeability index was significantly higher in EIB-positive asthmatics (0.031 +/- 0.009) than in EIB-negative asthmatics (0.020 +/- 0.005, p = 0.0011) and normal control subjects (0.008 +/- 0.003, p < 0.0001). We also found that there was a significant correlation between NO levels in induced sputum and the airway vascular permeability index (r = 0.525, p = 0.0101). Moreover, the airway vascular permeability index was significantly correlated with the severity of EIB (percentage of maximal fall in FEV(1) [r = 0.761, p = 0.0002], AUC(0-30) [r = 0.716, p = 0.0005]). However, this index was not significantly correlated with magnitude of eosinophilic inflammation.

Our findings suggest that increased airway vascular permeability due to excessive production of NO correlates with the severity of EIB in asthmatics, and that assessment of albumin flux in airway lining fluid stimulated by hypertonic saline solution is a sensitive predictor of the severity of EIB.