Diagnosing Nocturnal Asthma?
The easiest way to diagnose nocturnal asthma is to check a bedtime peak flow and a peak flow on awakening. If there is more than a 15% difference, you have significant nocturnal variability that may be the cause of your symptoms. However, peak flow meters may miss 50% to 80% of nighttime variability in FEV1. Thus, you and your provider may need to consider this and start a therapeutic trial.
Sources:
Sutherland ER. Nocturnal asthma. J Allergy Clin Immunol. 2005 Dec;116(6):1179-86.
Martin RJ. UpToDate. Nocturnal asthma. Accessed April 5, 2009.
