What peak flow measures

Peak expiratory flow, or PEF, is the highest airflow rate during a forced expiration. A portable meter enables repeated recordings when prescribed by a professional. It can support investigation of occupational asthma, but one reading does not establish diagnosis or identify the causative substance.

Why serial records are taken

Comparing work periods with time away from exposure can provide information on respiratory variation. The clinical team defines the plan, duration and conditions. Symptoms may be delayed and do not always disappear away from work. Absence of an obvious difference therefore does not automatically rule out an occupational relationship.

Technique and recording

Performance must be consistent, and the person needs practical instructions. Time, task, symptoms and other information considered necessary by the professional are recorded. Technique errors or device changes can distort comparison. A complete record includes measurement circumstances, not just values without a relationship to the working day.

Do not change treatment independently

The investigation plan must coordinate with clinical care. Medicines are not stopped or schedules changed to try to demonstrate a difference unless directed by the responsible professional. Nor is hazardous exposure deliberately created to obtain a measurement. Protecting the person takes priority over completing a data series.

Interpretation example

In a hypothetical example, records show changes after a particular task. The professional checks quality, timing, treatment and other possible causes and decides whether further tests are needed. The prevention team identifies agents and controls for that task. Temporal coincidence guides investigation but does not replace clinical confirmation or exposure assessment.

Using the results

PEF is useful when integrated with history, examination and indicated tests. Records contain health information and must be protected. Preventive conclusions may require avoiding or reducing exposure while investigation continues. Significant breathing difficulty needs immediate medical attention rather than waiting to finish the planned record.