Pocket-sized spirometer for monitoring bronchial challenge procedures

SUMMARY. Diagnosis of occupational asthma is verified by inhalation challenge testing when frequent monitoring of peak expiratory flow (PEF) or forced expiratory volume in 1 s (FEVj) is needed. FEV₁ measurements also allow frequent monitoring of changes in small airways. For the follow-up of lung function of suspected occupational asthma, a reliable, personal and mobile device is needed. We studied the accuracy of a pocket-sized spirometer, Micro Plus Spirometer (MP), compared with our former combination of two devices, i.e. the values of forced expiratory volume in 1 s (FEV₁) with those measured with the Vitalograph bellow spirometer (V); and the peak expiratory flow (PEF) values with the values obtained with a Wright PEF meter (W). In healthy control subjects, the values of FEVj obtained with Micro Plus correspond well to those obtained using a bellow spirometer (r= 0–97) and the mean difference (MP-V) was -0–06 1 irrespective of the mean FE V₁ value. W gives smaller PEF values than the MP; the mean difference in PEF (MP-W) was 44 1 min^-1, but the values increased linearly with increasing flow. The poor relation between PEF values might be based on the low reliability of the Wright device. In patient follow-up, the FEVj values measured with MP and V showed a good correlation (r= 0–99). The PEF values in patients increase linearly measured with W vs. MP with increasing flow values. In conclusion, we found the pocket-sized spirometer a handy and useful device for monitoring bronchial challenge procedures in patients with suspected occupational asthma. The number of exhalations during the challenge test follow-up is lessened when FEV₁ and peak expiratory flow (PEF) can be measured simultaneously.