Peak Flow Measurement

By Robbie Leinweber

(Peak Flow Meter, PFM, Peak Expiratory Flow Measurement)

Procedure Overview

What is peak flow measurement?

Peak flow measurement is a procedure in which air flowing out of the lungs is measured. The measurement obtained is called the peak expiratory flow rate (PEFR), or peak expiratory flow (PEF).

Peak flow measurement may be obtained using a spirometer, an instrument with a mouth piece that measures the amount of air breathed in and/or out and the rate at which the air is inhaled and expelled from the lungs. Peak flow may also be measured with a peak flow meter (PFM), a portable, hand-held device. Both devices take the measurement as an individual forcefully blows into the mouthpiece of the device.

Spirometry is usually performed in a doctor’s office, clinic, or a hospital. A peak flow meter is small and light enough to be used almost anywhere.<.p>

There are several types of PFMs available. However, it is important that one continues to use the same type of PFM on a consistent basis, as the PEFR can vary among different brands and types of meters.

Peak flow measurement using a peak flow meter is particularly useful for individuals with asthma. During an asthma flare-up, the large airways in the lungs slowly begin to narrow. This slows the speed of air leaving the lungs. A peak flow meter, when used properly, can reveal narrowing of the airways well in advanced of an asthma attack. Peak flow meters can help determine:

  • When to seek emergency medical care

  • The effectiveness of an asthma management and treatment plan

  • When to stop or add medication as directed by a doctor what triggers the asthma attack (such as exercise-induced asthma)

Other related procedures that may be used to diagnose problems of the lungs and respiratory tract include chest X-rays, bronchoscopy, bronchography, chest fluoroscopy, chest ultrasound, lung biopsy, lung scan, mediastinoscopy, oximetry, positron emission tomography (PET scan), pleural biopsy, pulmonary angiogram, pulmonary function tests, sinus X-ray, and thoracentesis. Please see these procedures for additional information.

Anatomy of the respiratory system

The respiratory system is made up of the organs involved in the interchanges of gases, and consists of the:

  • Nose

  • Pharynx

  • Larynx

  • Trachea

  • Bronchi

  • Lungs

The upper respiratory tract includes the:

  • Nose

  • Nasal cavity

  • Ethmoidal air cells

  • Frontal sinuses

  • Maxillary sinus

  • Larynx

  • Trachea

The lower respiratory tract includes the lungs, bronchi, and alveoli.

What are the functions of the lungs?

The lungs take in oxygen, which cells need to live and carry out their normal functions. The lungs also get rid of carbon dioxide, a waste product of the body's cells.

The lungs are a pair of cone-shaped organs made up of spongy, pinkish-gray tissue. They take up most of the space in the chest, or the thorax (the part of the body between the base of the neck and diaphragm).

The lungs are enveloped in a membrane called the pleura.

The lungs are separated from each other by the mediastinum, an area that contains the following:

  • The heart and its large vessels

  • Trachea (windpipe)

  • Esophagus

  • Thymus

  • Lymph nodes

The right lung has three sections, called lobes. The left lung has two lobes. When you breathe, the air enters the body through the nose or the mouth. It then travels down the throat through the larynx (voice box) and trachea (windpipe) and goes into the lungs through tubes called main-stem bronchi.

One main-stem bronchus leads to the right lung and one to the left lung. In the lungs, the main-stem bronchi divide into smaller bronchi and then into even smaller tubes called bronchioles. Bronchioles end in tiny air sacs called alveoli.

Reasons for the Procedure

A peak flow meter (PFM) can assist with the management of asthma. It can provide you and your doctor with information about how open the airways are in your lungs. The PFM can detect small changes in the large airways before you start to wheeze.

Using a PFM every day will let you know when your peak flows are starting to drop. This allows you to make early changes in your medication or routine to help prevent asthma symptoms from worsening. The PFM can also identify the value at which you will need to call your doctor or go to the emergency room.