Day-to-day changes in ventilatory function in relation to the environment: Part III. Frequent measurements of peak flow

As an extension of an earlier study of day-to-day variations in peak expiratory flow, measurements were made on two normal subjects before and after their daily journey to work, and at three times during the day. For one of these subjects there was some correlation between the change in peak flow on entering London each morning and the concentration of sulphur dioxide at the time, but in both the main feature was a consistent diurnal variation. As in earlier studies, respiratory infection was found to be the main factor causing reductions in the daily mean peak flow, while stress led to some increases in values. Peak flow measurements were also made twice daily on two bronchitic subjects and for one of them there was a relationship between the values at the end of the working day and the concentrations of sulphur dioxide (serving as an index of pollution in general). This relationship disappeared, however, when the clinical condition of the subject changed, and no consistent relationship with pollution could be found with results from the other subject.