How do I test peak flow using a peak flow meter (PFM)?

How to Test Peak Flow Using a Peak Flow Meter

To test peak flow, the patient should stand or sit upright, take a deep breath to full inspiration, place the mouthpiece just past the front teeth with lips sealed tightly around it, and blow out as hard and fast as possible. 1

Proper Technique for Peak Flow Measurement

Patient Position and Preparation

• The patient should be in a standing or sitting position 1
• The neck should be in a neutral position, not flexed or extended 1
• A nose clip is not necessary but may be used 1

Steps for Performing the Test

• Ensure the peak flow meter indicator is at the bottom of the scale (zero position) 1
• Have the patient take a deep breath to reach total lung capacity (maximum inspiration) 1
• The patient should place the mouthpiece just past their front teeth and seal their lips tightly around it 1
• The patient should blow out as hard and as fast as possible without hesitation 1
• The exhalation should be forceful and explosive rather than prolonged 1
• Record the value indicated on the meter 1
• Reset the meter and repeat the procedure two more times 1
• Record the highest of the three readings as the peak expiratory flow rate (PEFR) 1

Common Errors to Avoid

• Hesitation during the manoeuvre which can reduce the peak flow value 1
• Obstruction of the mouthpiece with the tongue 1
• Coughing during the manoeuvre 1
• Leakage of air around the mouthpiece 1
• Slow or unforced exhalation which will result in falsely low readings 1

Interpretation and Documentation

Recording Results

• The highest value from three attempts should be recorded 1
• Results are expressed in liters per minute (L/min) on most portable devices 1
• For monitoring purposes, measurements should be taken at the same time each day, typically morning and evening 1

Monitoring Over Time

• For home monitoring, patients should record their best of three PEF readings twice daily (morning and evening, before treatment) 1
• The average peak flow should be calculated from at least five days of recordings 1
• A variability of >10% in adults and >13% in children may be suggestive of asthma 1
• Diurnal variation is calculated as the day's highest PEF minus the day's lowest PEF, divided by the mean PEF for the day 1

Equipment Considerations

Types of Peak Flow Meters

• Various portable peak flow meters are available (Mini-Wright, Assess, Pulmo-graph, Wright Pocket meters) 2
• Digital peak flow meters that connect to smartphones are now available for home monitoring 3
• The accuracy and reproducibility may vary between different models 4, 2

Maintenance and Hygiene

• The peak flow meter should be cleaned regularly according to manufacturer's instructions
• Each patient should have their own personal peak flow meter for home use to prevent cross-contamination 5
• In clinical settings, disposable mouthpieces should be used for each patient 1

Clinical Applications

Uses in Respiratory Conditions

• Peak flow monitoring is particularly useful in diagnosing and monitoring asthma 6
• It can help detect early changes in airway function before symptoms occur 5
• It can be used to assess response to bronchodilator therapy 1
• It helps in monitoring disease progression and treatment effectiveness 5

Limitations

• Peak flow is effort-dependent and requires proper technique for accurate results 1
• Different peak flow meters may give different readings, so the same device should be used consistently for an individual patient 2
• Peak flow variability testing alone is not recommended as the primary objective test to diagnose asthma in children aged 5-16 years 1

By following these standardized steps, patients and healthcare providers can obtain reliable peak flow measurements that are valuable for monitoring respiratory conditions and guiding treatment decisions.