PEF Measurement

Question 1

What is PEF?

Answer 1

Measure of how quickly air can be expelled from the airways.

• Maximum flow achievable from a forced expiration starting at full inspiration with an open glottis
• Measured at the mouth
• Reflects sum of all different resistances to flow from all generations of the bronchi
• Litres per second
• Can be measured with a small portable meter or as part of a spirometry manoeuvre
• PEF is reached early in a blow

Question 2

Circadian Rhythm - PEF

Answer 2

• Varies during day in HEALTHY individuals
• Morning Dip
• Normal for airways to narrow slightly at night

Question 3

Procedure for measuring PEF

Answer 3

• Ensure meter is clean and in working order
• Prepare equipment/set recording needle to zero
• Sitting or standing is acceptable
• Explain purpose and nature of the test
• Patient any questions
• Gain Consent
• Ensure meter is held in horizontal position
• Ensure patients hands do not obstruct any exhaust holes or impede movement of the pointer

Question 4

Procedure 2

Answer 4

• Ask patient to take a full inspiration through their mouth
• Place lips/teeth around mouthpiece to form a tight seal
• Pointer returned to zero and patient given time to recover
• Highest reading of 3 technically acceptable blows should be recorded ( 2 largest values within 40 Litres per min
• A demo is useful

Question 5

Common Errors

Answer 5

• Poor Patient Effort (comprehension, motivation and co-ordination
• Incomplete inspiration prior to exhalation
• Leaks around the mouthpiece: Poor Seal/ Loose fitting dentures
• Tongue Obstructing Mouthpieces, Facial Palsy
• Inadequate rest between attempts
• Not Setting ‘pointer’ to Zero
• Covering exhausts holes with hands

Question 6

Indications for Measuring PEF

Answer 6

• Diagnostic and Monitoring of Asthma
• Monitoring of treatments/interventions
• Asthma Managements Plans
• Measurement of Bronchodilator response/ Steroid trials
• Occupational Monitoring

(Peak Cough Measurements )

Question 7

Advantages of PEF:

Answer 7

• Small and Portable Equipment
• Facilitates serial and domiciliary measurements
• Quick to Perform and Use
• Cost Effective
• Does not require mains Power Supply

Question 8

Limitations of PEF

Answer 8

• Effort Dependent
• Long Term Compliance may be a problem for some patients
• Technique may cause spuriously high values (coughing/spitting)
• Patients may ‘make up’ results on PEF diaries
• Patients need to be encouraged to clean meter at regular intervals
• Meters require care - fragile and easy to damage
• Unable to calibrate
• Only measures flow
• Measures large airflow only (central)
• Normal ranges are wide/ do not encompass ethnic diversity
• Not as reproducible as FEV1

Question 9

Equipment

Answer 9

• PEF meter
• Electronic
• PEF diary
• Height measuring devices

Question 10

Percent Change

Answer 10

% change = 100 x (Post PEF-Pre PEF) / (pre-PEF)

Question 11

Occupational Monitoring

Answer 11

• Used in diagnosis and monitoring