Reproducibility of late phase pulmonary response to exercise and its relationship to bronchial hyperreactivity in children with chronic asthma

Abstract

To determine the reproducibility of the delayed response to exercise and its effect on bronchial hyperreactivity, we had 26 asthmatic children perform treadmill exercise challenge on two occasions 1 week apart. Both challenges were preceded by 2 control days and 1 histamine challenge day, and were followed by another histamine challenge day. Peak expiratory flow rate (PEFR) was measured hourly for 12 hours on each control day and for 12 hours after each exercise or histamine challenge. During the first week, five patients showed a late reaction (PEFR change > 15%) after exercise, which was present in only two of them the following week. These two patients, however, also showed a spontaneous fall > 15% of PEFR from baseline during the other control study days. A similar pattern was seen in two other patients who had a late response during the second exercise challenge but not during the first. No significant change occurred in histamine PC-20 FEV1 between before and after the exercise challenges. An apparent late asthmatic response after exercise challenge may represent a within-day fluctuation in pulmonary mechanics that develops spontaneously in children with asthma.

Occurrence of a late response to exercise in asthmatic children: multiple regression approach using time-matched baseline and histamine control days

“…This is not the first study of the occurrence of a LAR after exercise in asthmatic subjects. The results presented are in agreement with those of RUBINSTEIN et al [19] and of BONER and co-workers [23]. In contrast, other investigators have described the existence of a LAR after exercise in asthmatic children [11,13,16].…”

“…In our study, the children were treated for their asthma at an out-patient clinic. Other investigators have used a study group of asthmatic children, resident at special asthma clinics [16,23]. It could be argued that the latter population may have suffered from more severe and uncontrollable asthma, which is often the reason for referral to specialized clinics.…”

“…Among the 13 studies cited [11][12][13][14][15][16][17][18][19][20][21][22][23], only four used randomized study days [16,[20][21][22]. The choice of "adequate" control days to establish normal diurnal variation in lung function can be considered to be of vital importance [24].…”

“…However, nearly as many studies have been unable to document a LAR [18][19][20][21][22][23]. The experimental design of some of the studies showing a LAR has been criticized because of the lack of "appropriate" control days [24], during which lung function is being documented without exercise or following bronchoconstriction induced by inhaled histamine.…”

“…Furthermore, when evaluating the results of these studies, there seems to be considerable lack of agreement among the various investigators on the definition of the LAR after exercise. The LAR has been defined as either a 10% [12,15], 15% [14,20,23] or 20% [16,17,19,21], fall in lung function (e.g. the forced expiratory volume in one second (FEV1)) during different time-periods after exercise challenge.…”