In: Asthma28 Jan 2013
The coefficient of variation of PEFR on the control day was 4.6 ±3.1 percent for the entire group of 81 patients who performed EC and 6.7 ±2.5 percent for 17 patients with a LAR.
On the basis of McNemars test (Table 2), the hypothesis that a LAR after EC with a PEFR fall of ^ 20 percent does not occur more often on the exercise day than on the control day therefore had to be rejected (p = 0.008). Buy Asthma Inhalers Online
The magnitude of the early and the late drop in PEFR on the exercise day in the entire group of 81 patients who performed EC was significantly correlated, although the correlation coefficient was small (r = 0.33; p<0.01). The early PEFR fall (18.9 percent) was significantly greater than the late PEFR fall (9.5 percent) (p = 0.0001).
Repeated measurements analysis of variance revealed that the mean level of PEFR after EC was significantly lower on the exercise day than on the control day (p = 0.004). Also, the mean level of PEFR 4 to 13 hours after EC was significantly lower on the exercise day than on the control day (p = 0.01).
For the 17 patients in whom PEFR fall was more than 20 percent 4 to 13 hours after EC, PEFR values on the control and the exercise day were compared at similar time points in graphs taking baseline value at the beginning of the day as 100 percent. There were two subgroups: (a) eight patients in whom late PEFR decreased ^20 percent on the exercise day as compared with the control day on at least three successive points of measurement (Fig 1); these were considered patients with a LAR, probably not caused by medication withdrawal (real LAR); (b) nine patients in whom late PEFR on the exercise day and the control day showed no consistent difference (Fig 2); in these subjects, a reason for the fall in PEFR was not clear (pseudo LAR). The characteristics of the patients with a fall in PEFR <20 percent, a real LAR, and a pseudo LAR are compared in Table 3.
Table 2—Comparison of a Late Fall in PEFR* from Baseline on the Control and Exercise Day (No. of Patients)
Table 3—Characteristics of Patients with a Late Fall in PEFR <20%, A Real LAR, and a Pseudo LAR
|PEFR fall <20%||Real LAR||Pseudo LAR|
|No. of patients||64||8||9|
|Age, yr, mean ± SD||23.8 ±12.7||29.9± 11.1||33.8 ±10.9|
|FVC, % predicted, mean ± SD||104.2 ±18.4||107.4 ±9.2||91.4 ±20.7|
|FEVI, % predicted, mean±SD||90.3±23.1||87.3 ±19.1||80.5±24.0|
|Histamine PC20, mg/ml, mean ± SD||1.1 ± 1.6||1.3±2.1||0.1±0.1|
|Corticosteroids: none/oral/inhaled/both (No. of patients)||6/4/35/19||2/1/3/2||1/2/1/5|
|EAR^20% (No. of patients)||18||5||6|
Figure 1. Peak expiratory flow rate (PEFR) on the exercise day and control day in 8 patients with a real late asthmatic response (LAR) after exercise challenge (EC). Baseline PEFR has been taken as 100 percent reference value.
Figure 2. Peak expiratory flow rate (PEFR) on the exercise day and control day in nine patients with a pseudo late asthmatic response (LAR) after exercise challenge (EC). Baseline PEFR has been taken as 100 percent reference value.
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