Limitations in the use of median frequency for lung sound analysis

摘要

The aim of this paper is to investigate methods of standardizing lung sound analysis, with a view to supplementing traditional spirometric air flow measurements to help in the diagnosis of asthma and to provide a measure of the effectiveness of treatment. Lung sounds were measured in nine patients with asthma and five control subjects, alongside air flow measurements of forced expiratory volume (FEV{sub}1) and forced vital capacity (FVC). The patients were administered the broncho-dilator, salbutamol, to assess how effective these measurement techniques were for quantifying its effect. The results agree with previous studies, that analysis of lung sounds is a potentially useful tool for indicating air flow changes. The results, however, also demonstrate that the emerging standard of 'F{sub}50' or 'median frequency' should be treated with great caution because of its high sensitivity to the measurement frequency range. F{sub}50 is very unlikely to provide a reliable single indicator of lung condition.