Measurement of reversibility of airways obstruction: which parameters to use?

Maximum expiratory flow-volume (MEFV) curves recorded before and after salbutamol inhalation on 100 patients with various lung diseases were studied. Improvement was found to occur more frequently in MEF50, FEF25-75, FVC and MEF25, than in FEV1, FEV1/FVC%, or MTT. If improvement in only one of the first four parameters was taken as a measure of reversibility of airways obstruction, many cases showing improvement in the others were missed. Improvement in any of the last three parameters was rarely missed if improvement in any of the first four was present. It was concluded that there is no single best measurement for assessment of bronchodilator response. FVC, FEF25-75, MEF50 and MEF25 should all be measured. A flow-volume record of forced expiration from which all these measurements can be derived would therefore be preferable for this purpose to the time-volume spirometer record from which only FVC and FEF25-75 can be determined.