Peak flow

Question 1

What is the equipment involved in peak flow?

Answer 1

-peak flow meter
-disposable mouthpieces (one way valves)
-one way valve stops patient breathing in from equipment (reduces infection risk).

Question 2

How do you perform a peak flow meter measurement?

Answer 2

-attach mouthpiece to peak flow meter
-move pointer to 0 position
-ask patient to breathe in to TLC, put mouthpiece into mouth
-keep peak flow meter horizontal
-patient gives short, sharp puff into meter
-remove and record value
-reset pointer and repeat twice

Question 3

What are some errors in peak flow measurement?

Answer 3

-poor effort
-leaks around mouthpiece (not a tight seal from lips)
-inadequate rest between attempts
-fingers occluding pointer on peak flow meter

Question 4

What is sequential peak flow monitoring?

Answer 4

recording peak flow over a period of time, recorded 2-4 times a day, record in peak flow diary for at least 2 weeks.

Question 5

What other factors can a peak flow diary record?

Answer 5

-symptoms (cough, if breathing affects sleep)
-aggravating factors
-use of inhalers (which ones, how much, what time?)
-work periods/ holidays (occupational asthma).

Question 6

What is variability?

Answer 6

Difference between min and max PEF. Normal daily variation peak flow is 8%.
Variation above 20% in indicative of asthma.

Question 7

How do you calculate variability?

Answer 7

(max PEF- min PEF)/ Max PEF x100

Question 8

What are the limitations of peak flow?

Answer 8

-effort dependent (trust and rapport, explanation of procedure), motivation of patient
-usually comply with PEF monitoring over short time and unlikely to comply with long term measurements
-produce unusually high measurements by coughing or spitting into meter
-patient can falsify results (want to prove how ill they are)
-if patient doesn’t clean meter, moisture build up and cause errors