Diagnosis of Asthma With Peak Expiratory Flow Rate
What is a peak expiratory flow rate?
Peak Expiratory Flow Rate (PEFR) aka peak respiratory rate is a test that measures how fast a person can exhale. This test examines lung function and is often used by patients who have asthma.
Asthma is a chronic condition characterized by inflammation in the respiratory tract. Common symptoms of asthma include shortness of breath that worsens with accompanied by activity, wheezing, and coughing. Airflow exhaled from the lungs can be restricted due to inflammation or blockage due to excess mucus.
PEFR tests are usually performed at home with cheap handheld devices called peak flow monitors. Both electric and non-electric appliances are available for purchase. The device is easy to use, and most patients over the age of five can read the results accurately.
In order for the PEFR test to be beneficial, the patient must keep a continuous record of its flow rate. Otherwise, the patient will not see the pattern that occurs when the flow rate is low or decreased.
These patterns can help individuals prevent symptoms from getting worse before full asthma attacks occur, for example. Each person will know when they need to adjust their environment or treatment, or make an appointment with the doctor. The PEFR test is also called the peak flow.
Why should we do peak expiratory flow rate test?
The PEFR test is a simple, general test that helps to diagnose and monitor lung problems, such as:
- asthma
- chronic obstructive pulmonary disease (COPD)
- lung transplant that is not working properly
This test can also be done at home to determine whether the treatment of lung disorders works and to prevent the condition from getting worse. Keeping a continuous record of the peak flow rate can also help the patient to determine whether environmental factors or certain pollutants influence it to breathe.
How to perform peak expiratory flow rate test?
The PEFR test is performed with an expiratory peak current monitor. It is a simple handheld with a funnel at one end and a scale on the other. A small plastic arrow moves as the air is blown into the funnel, measuring the speed of the airflow.
When you perform a test, you will:
- Take a deep breath as you can
- Blow into the funnel as fast and as hard as you can. Do not put your tongue in front of the funnel
- Do this three times
- Record the top speed of three
If you cough or sneeze while exhaling, you need to repeat it again.
How often do I have to do this test?
To determine the "best thing," the patient should measure their peak flow rate:
- at least twice a day for two to three weeks
- in the morning, when waking up, and in the afternoon or evening
- 15 to 20 minutes after using inhalation, quick-acting beta2-agonist (asthma remedy)
The common beta2-agonist drug is albuterol, under the brand name Proventil and Ventolin. It will relax the muscles surrounding the airways and help increase the caliber of the breathing.
What preparation is required for the peak expiratory flow rate test?
PEFR is a simple test that does not require much preparation. You probably should not wear tight clothes that might prevent you from breathing deeply. Stand up or sit up straight, and focus.
What is the normal result of a peak expiratory flow rate test?
Normal test results vary depending on your age, gender, and height. Results are more useful when compared to your current reach in the past.
You can check your results by comparing them to this ratio provided by Monash University. This ratio shows the level of normal peak flow associated with height (MU):
Height (cm) = PEFR (L / min)
120 cm = 215 L / min
130 cm = 260 L / min
140 cm = 300 L / min
150 cm = 350 L / min
160 cm = 400 L / min
170 cm = 450 L / min
180 cm = 500 L / min
Small changes may not mean anything significant. If you see a significant drop in your peak flow rate, it may be caused by a recurrence of your lung disease. It is also possible if other symptoms occur, such as:
- cough worsened
- hard to breathe
- sigh or hoarse breath
If you are worried about the outcome, you may want to visit a doctor and get a more accurate reading with a spirometer. A spirometer is considered as a more advanced peak flow monitoring device. For this test, you will breathe through a funnel connected to a spirometer machine that measures your breathing rate.
What is the meaning of abnormal results in peak expiratory flow rate?
The flow rate decreases when the respiratory tract is blocked. Asthmatic patients may experience low levels of peak flow before they develop respiratory symptoms.
