Home peak expiratory flow rate (PEFR) monitoring can be extremely helpful for people with moderate or severe asthma. Information from this simple test can guide decisions about when to start or stop medications and when to seek emergency care. Daily PEFR measurements also help to identify patterns of airway obstruction that may indicate a need for additional treatment.
The PEFR test involves inhaling as much air as possible into the lungs and then blasting the air out of the lungs as quickly as possible, exhaling into the meter. This quick test reflects three factors: the diameter of the upper and large airways; the strength of the muscles of exhalation; and the person’s effort and coordination during a test. After this inhaling-exhaling maneuver has been performed a few times, the last two factors usually remain constant, thus the PEFR measures changes in degree of airway obstruction.
Variable Air Flow
Flow rates are usually lowest, reflecting increased airway obstruction, in the early morning. This is known as the bathyphase or “morning dip.” Rates are usually highest, reflecting decreased obstruction, in the afternoon. This is the acrophase. Everyone’s lungs exhibit this pattern, but it is exaggerated in people with asthma.
A decrease in PEFR from a “personal best” reading or predicted personal best reading suggests the onset of an asthma episode. High variability in PEFR readings is a sign of increased airway hyperreactivity and usually suggests the need for antiinflammatory medications. Evening dips below morning PEFR levels may indicate the need to change the dose or timing of medications. PEFR measurements also can be valuable during sudden episodes of breathlessness to determine whether air flow obstruction is present. If the value remains within the individual’s normal range, the breathlessness may be due to panic or anxiety, in which case relaxation strategies can be helpful.
Using a Peak Flow Monitor
A trained nurse or other health-care professional should demonstrate how to use a home peak flow monitor. Then the patient should perform at least three correct maneuvers. The patient is then sent home with a meter and diary, and usually asked to record the highest of three consecutive PEFR values obtained up to four times a day: first thing in the morning, before medications; around noontime; between 4 P.M. and 7 P.M.; and at bedtime. Often, such monitoring is necessary for only one to two weeks for a physician to determine an appropriate treatment plan. After that, the patient may need to use the meter only when symptoms change.
Much of the day-to-day responsibility for managing asthma falls on the patient and the patient’s family. Home peak flow monitoring allows patients to be informed partners with their physicians and achieve optimum control of symptoms. Home peak flow monitoring allows patients to be informed partners with their physicians and achieve optimum control of symptoms