A critical review of the studies of the effects of simulated or real gastroesophageal reflux on pulmonary function in asthmatic adults.

OBJECTIVE To identify and critically review the published peer-reviewed, English-language studies of the effects of both spontaneous and simulated gastroesophageal reflux (GER) on pulmonary function in asthmatic adults. DESIGN Using the 1966 to 1997 MEDLINE database, the terms asthma and lung disease were combined with GER to identify studies of the effects of GER and acid perfusion (AP) of the esophagus on pulmonary function. The bibliographies were also reviewed. Studies of asthmatics with and without symptomatic GER were analyzed both together and separately. RESULTS A total of 254 citations, including 180 published in English, were identified. Among these were 18 studies of GER and AP in asthmatic adults. These reports, which contain data on 312 asthmatics, found that the FEV1 and the midexpiratory rate did not change during AP and GER in the studies containing 97% and 94% of the asthmatics, respectively. Flow volume loop indexes, including the flow at 50% of the vital capacity (V50), flow at 25% of the vital capacity, and the peak expiratory flow rate, did not change during AP or GER in the studies with 77%, 60%, and 65% of the asthmatics, respectively. Small changes in the resistance were reported in the studies containing 42% of the asthmatics. Among asthmatics without symptomatic GER, no changes in spirometry, resistance, and flow volume indexes were found, except for a 10% decline in V50 in one study with seven subjects. CONCLUSIONS In asthmatics with GER, the effects of AP on pulmonary function are minimal, and only a minority are affected. The literature does not support the conclusion that asymptomatic reflux contributes to worsening lung function.