Perception of airway narrowing during reduction of inhaled corticosteroids and asthma exacerbation.

BACKGROUND: The perception of airway narrowing is reduced in subjects with severe asthma and may be related to the severity of airway inflammation. A study was undertaken to determine if the perception of airway narrowing changes during the reduction of inhaled corticosteroid (ICS) dose or during an asthma exacerbation.
METHODS: Forty two asthmatic subjects with well controlled asthma had their daily ICS dose halved every 2 months until they were weaned off ICS or they developed an exacerbation. Perception was measured at baseline and at monthly intervals during bronchial challenge with mannitol as the slope and intercept of the regression of the Borg score and percentage fall in forced expiratory volume in 1 second (FEV(1)), and as the Borg score at 20% fall in FEV(1) (PS(20)FEV(1)). Sputum was collected for measurement of inflammatory cell numbers.
RESULTS: In 33 subjects who successfully halved their ICS dose without exacerbation there were significant reductions in slope (p = 0.01), intercept (p = 0.01), and PS(20)FEV(1) (p = 0.003). Sputum eosinophils and airway hyperresponsiveness increased significantly but, in 14 subjects from whom sputum was obtained, changes in eosinophils were not correlated with changes in perception. Change in airway hyperresponsiveness correlated with change in PS(20)FEV(1) (r = -0.40, p = 0.025). In 27 subjects who developed an exacerbation, slope decreased (p = 0.02) and intercept increased (p = 0.01) compared with the visit before the exacerbation. Changes in intercept correlated with changes in resting FEV(1) (r = -0.57, p = 0.002).
CONCLUSIONS: Perception of airway narrowing decreases during ICS dose reduction and decreases further during a mild asthma exacerbation. These changes are related to concurrent changes in airway hyperresponsiveness and resting lung function. The effect of changes in airway inflammation on perception is unclear.