What does a peak expiratory flow rate device measure?

A peak expiratory flow rate (PEFR) device measures the velocity or speed of air that is forcefully exhaled from the lungs. This measurement is critical for assessing and monitoring lung function, especially in individuals with asthma or other respiratory conditions. By determining how quickly a person can expel air from their lungs, healthcare providers can evaluate the degree of airway obstruction and responsiveness to treatment.

The PEFR reflects the maximum flow rate achieved during a forced expiration from a position of maximal inhalation, making it a valuable tool in managing respiratory diseases. It is particularly useful for tracking changes over time, allowing patients and clinicians to identify trends that may indicate worsening control of asthma or the presence of airflow obstruction.

Understanding this measurement is important, as it directly relates to airway resistance and functionality rather than the volume of air inhaled, the residual volume in the lungs, or the inspiratory capacity. These other measures focus on different aspects of lung function and do not provide the same information about the speed of airflow during exhalation.