Refractoriness to inhaled mannitol 3 hours after allergen challenge

Area of Science:

• Pulmonary Medicine
• Allergy and Immunology
• Respiratory Physiology

Background:

• Indirect airway challenges, such as mannitol, can trigger mast cell mediator release and temporary airway refractoriness.
• Allergen challenges in asthma patients typically increase airway hyperresponsiveness to direct stimuli like methacholine.
• Understanding differential airway responses post-allergen exposure is crucial for asthma management.

Purpose of the Study:

• To investigate and compare the effects of allergen challenge on airway responsiveness to both direct (methacholine) and indirect (mannitol) stimuli.
• To assess these changes specifically at the 3-hour mark after allergen challenge completion.

Main Methods:

• A randomized clinical trial involving ten atopic asthma patients.
• Measurement of methacholine and mannitol provocation doses (causing 20% and 15% FEV1 decrease, respectively) 24 hours before and 3 hours after allergen challenge.
• Allergen challenges were separated by 7 to 14 days to ensure independence of effects.

Main Results:

• Allergen challenge led to a significant increase in airway responsiveness to methacholine (P = .02).
• Conversely, airway responsiveness to mannitol significantly decreased, requiring nearly double the dose post-allergen challenge (P = .02).
• Early allergen responses showed maximum percent decreases in FEV1 of 29.7% (methacholine) and 27.8% (mannitol).

Conclusions:

• Three hours after allergen challenge, airways become hyperresponsive to methacholine.
• Simultaneously, a significant refractoriness to indirect stimuli, exemplified by mannitol, develops.
• These findings highlight distinct temporal changes in airway reactivity following allergen exposure in asthma.