Lung epithelial permeability and inhaled furosemide: added dimensions in asthmatics

Lung clearance rates of inhaled (99m)Tc-DTPA aerosols constitute a sensitive index to evaluate the permeability changes characteristic of airway epithelial damage. It was thought that edema of the airway wall which is reported in asthma could be relieved with a diuretic like furosemide, helping to relieve the symptoms. We intended to study the effect of inhaled furosemide on lung epithelial permeability in asthmatics and smokers with the help of (99m)Tc-DTPA lung clearance test (LCT).

The study included three groups (n = 15), viz. normal healthy controls, asymptomatic chronic smokers, and chronic persistent asthmatics. Each subject underwent the LCT twice, baseline and post-furosemide (Lasix) study, within a week's interval. The post-furosemide study was carried out 15 min after inhalation of 10 mg of lasix. Lung epithelial permeability was determined in terms of clearance half-life (T (1/2)).

The baseline mean T (1/2) values for controls, smokers, and asthmatics were 50.95 +/- 16.58, 20.81 +/- 5.47, 24.06 +/- 6.19 min, respectively. Post-lasix T (1/2) values were 50.83 +/- 15.84, 20.70 +/- 5.65, 41.27 +/- 15.07 min, respectively. There was a significant difference (P < 0.001) in baseline and post-lasix clearance values in asthmatics only.

Baseline lung epithelial permeability was altered in smokers and asthmatics compared to the controls. Furosemide was effective only in asthmatics in reverting the permeability almost back to the normal range. Inhaled furosemide was effective even in moderate and severe asthmatics. Furosemide has multiple mechanisms of action. It possibly acts at bronchial level in view of the pathology in asthmatics lying in the airways.