5. Peak Expiratory Flow RatePeak Expiratory Flow Rate
(PEFR)(PEFR)
Measures how fast a person can exhale air
Requires a peak expiratory flow monitor
OmronMini-Wright AM2 Plus
6. PEFR VariabilityPEFR Variability
Asthma Diagnostic Clues:
• PEF Variability > 20%
(basis: home monitoring 2-4x/day
for 1-2 weeks)
• Improvement in baseline PEF by
20% after a 2-week therapeutic
trial
PEFmax - PEFmin
PEFave
(pm, post-bd) (am, pre-bd)
% Variability = X 100
0
50
100
150
200
250
300
350
1 2 3 4 5 6 7
Days
PEFR(L/min)
pm PEFR
am PEFR
17. Is it Asthma?
Determine that the patient is
experiencing episodic symptoms
of airflow obstruction
Demonstrate that the
obstruction is at least partially
reversible
Exclude alternate diagnoses