Abstract
Exacerbation of asthma has a negative impact on quality of life and increases the risk of fatal asthma. One of the known risk factors of patients with a history of near-fatal asthma is experiencing mild asthmatic symptoms as opposed to airway obstruction. We set out to find patients carrying such a risk before they experience severe exacerbation of asthma.
To determine the character of such patients, we compared the background and asthma diaries (mean period, 274 days) of 53 asthma patients with their symptoms and peak expiratory flow value (PEF). According to the criteria of the Japanese Society of Allergology, symptoms were classified into 8 categories ranging in severity from absent to severe attack.
Average PEF was 75.2% (50.5–100) in absent, 64.5% (36.6–92.6) in wheeze, 57.3% (25.0–94.7) in mild attack and 43.6% (20.4–83.1) in moderate attack, and the personal best was 100%. Thus, differences in decreased PEF in cases with the same symptoms varied widely between patients. PEF in wheeze, mild and moderate attack did not correlate significantly with the duration of asthma, FEV1 or the proportion of personal best to standard PEF. These PEFs did not show a significant difference in the groups that were divided by regular treatment of asthma, but did show a significant negative correlation with the coefficient of variation of PEF when asthma was absent.
To reveal patients who are insensitive to dyspnea, the most important factor to consider is the coefficient of variation of PEF when asthma is absent. When we find such patients who exhibit fluctuant PEF, we have to intervene in their treatment, even when they claim to be stable.
- © 2011 ERS
