SPIROMETRY AND VENTILATION-PERFUSION INEQUALITY IN PATIENTS WITH MILDALLERGIC-ASTHMA BEFORE AND DURING THE POLLEN SEASON

Several studies on asthma have shown a low correlation between gas exc hange and spirometry, especially after treatment with bronchodilators. The aim of the present study was therefore to examine both spirometry results and gas exchange during a pollen-free period and at the end o f the pollen season in patients with mild and well-controlled allergic asthma. Pulmonary gas exchange was studied using a modified form of t he multiple inert gas elimination technique. Lung volumes and forced e xpiratory flows were measured by common spirometry. During the non-pol len season, spirometry and forced expiratory flows were within the ref erence values in all but one patient, who had decreased indices for ai rway flow. Three other patients showed signs of minor gas exchange imp airment. During the pollen season, FRC was slightly increased (P < 0.0 5) and MEF(50) was slightly decreased (P < 0.05) for the group. Two pa tients had an increased index for gas exchange impairment (log SDQ was 0.64 and 0.59) and four patients had borderline log SDQ (0.50 to 0.56 ). However, the mean log SDQ was not increased in the pollen season. T he results show that, both in the pollen season and in the pollen-free season, low degrees of gas exchange impairment could be present in po llen allergic asthmatic patients despite normal spirometry. The low de gree of gas exchange impairment in some patients indicates the presenc e of airway inflammation with oedema and/or secretion. However, high d egrees of ventilation-perfusion inequality were not observed in these patients where air now rates were mainly normal.