Aim: Recording Force of Air Expelled Using a Peak Flow Meter
Introduction:
A Peak Flow Meter (PFM) is a simple, portable, handheld device used to measure how fast a person can blow air out of their lungs. This measurement is known as the Peak Expiratory Flow Rate (PEFR) and reflects the function of the lungs and airway resistance. It is especially helpful in the monitoring and management of respiratory conditions such as asthma. Regular monitoring allows patients and healthcare professionals to detect early signs of airway narrowing and take timely action.
Materials Required:
- Peak Flow Meter
- Peak Flow Diary/Chart
- Alcohol wipes or disinfectant
- Healthy volunteers or patients
Procedure:
- Preparation: Ensure the peak flow meter is clean and reset (marker at zero or lowest scale). Ask the subject to stand upright to allow full lung expansion.
- Inhalation: The subject takes a deep breath, filling the lungs completely.
- Blowing into the Device: The mouthpiece is placed in the mouth, lips sealed tightly around it (do not block with the tongue). The subject blows out as hard and as fast as possible in a single forceful breath.
- Recording the Reading: Note the reading where the marker stops. Repeat the procedure three times, and record the highest value as the final PEFR reading.
- Personal Best Value: The personal best PEFR is the highest value recorded over a 2-week period when the person is feeling well. This becomes the reference for interpreting asthma control.
Zones Based on Personal Best (Asthma Action Plan – AAP):
| Zone | PEFR Range | Interpretation |
| Green Zone | 80–100% of personal best | Good control – continue regular medications |
| Yellow Zone | 60–80% of personal best | Caution – airway narrowing; follow AAP steps |
| Red Zone | <60% of personal best | Danger – severe obstruction, seek emergency help |
Sample Data Table: PEFR Readings
| Subject No. | Name/ID | Trial 1 (L/min) | Trial 2 (L/min) | Trial 3 (L/min) | Best Reading (L/min) | Remarks |
| 1 | Subject A | 370 | 390 | 400 | 400 | Within green zone |
| 2 | Subject B | 250 | 260 | 255 | 260 | Yellow zone alert |
| 3 | Subject C | 180 | 200 | 190 | 200 | Borderline red zone |
| 4 | Subject D | 420 | 410 | 430 | 430 | Healthy lung output |
Precautions:
- Always ensure the subject is standing straight during measurement.
- The peak flow meter must be clean and reset before each use.
- Take multiple readings and always record the highest.
- Do not allow the subject to cough or take shallow breaths during the test.
Conclusion:
Peak flow measurement is a valuable, quick, and non-invasive method to assess lung function and monitor asthma control. When combined with an Asthma Action Plan, it helps in timely decision-making and effective disease management.