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Peak expiratory flow rate as a discriminator in acute exacerbation of COPD

Three Part Question

In [patients with an acute exacerbation of chronic obstructive pulmonary disease] is [peak expiratory flow rate] a [useful discriminator of exacerbation severity]?

Clinical Scenario

A 60 year old woman presents to the emergency department with an acute exacerbation of COPD. In the course of your initial assessment you wonder if taking a peak flow measurement will help you assess the severity of the exacerbation.

Search Strategy

Medline 1966-03/05 using the OVID interface.
[ OR exp Pulmonary Disease, Chronic Obstructive OR OR Chronic obstructive airways OR exp Lung Diseases, Obstructive OR exp Pulmonary Emphysema OR Emphysema$.mp OR exp Emphysema OR Chronic OR exp Bronchitis Chronic OR exp Bronchitis] AND [exp Acute Disease OR Acute OR OR Acute] AND [ OR exp Triage OR exp Severity of Illness Index OR Severity OR exp Risk Assessment OR Risk OR exp forced expiratory flow rates OR OR exp Spirometry OR OR exp Peak Expiratory Flow Rate OR peak expiratory flow OR Peak OR exp Respiratory Function Tests OR exp Forced expiratory flow rates] LIMIT to Human AND English language AND All Adult

Search Outcome

1597 papers were found of which only 2 were relevant to the three-part question. The relevant papers are shown in the table below.

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
Cham GW et al,
141 consecutive patients presenting to 2 ED's with clinical signs of severe or life threatening bronchospastic exacerbations of asthma or COPD. Markers of ARAProspective observational study of consecutive patients presenting to the ED.PEFR has a diagnostic marker of severity of bronchospasmPEFR only obtainable in 60 (47.2%) patients (58.3% in severe and 42.9% in life threatening category). Overall PEFR was not considered a useful diagnostic marker of severity.COPD and asthma patients studied together using severity criteria established for asthma. PEFR was included in the initial inclusion assessment. Clinically mild/moderate exacerbations were excluded.
Emerman CL & Cydulka RK,
199 patients, over the age of 50, presenting with acute exacerbations of COPD, able to perform spirometry. PEFR vs FEV1Diagnostic studyFEV1/PEFR, % of predicted normal valuesCorrelation between absolute values r=0.84 (p<0.0001) and PPV values r=0.81 (p<0.0001)Patient selection criteria exclude those with more severe exacerbations.


No studies answer this three-part question directly. No studies demonstrate PEFR as a useful marker of severity of an exacerbation of COPD. The paper by Emerman and Cydulka shows that in general there is good correlation between PEFR & FEV1 in patients presenting with an acute exacerbation of COPD. However the paper by Cham et al shows that the nature of exacerbations of COPD often precludes uniform or reliable measurements of PEFR in the emergency department setting and that other discriminators are more useful as markers of severity. Further research in to discriminators of exacerbation severity in COPD patients would be useful.

Clinical Bottom Line

In patients presenting to the ED with exacerbations of COPD, there is no evidence to support the use of PEFR as a useful discriminator of severity of illness.

Level of Evidence

Level 3 - Small numbers of small studies or great heterogeneity or very different population.


  1. Cham GW, Tan WP, Earnest A et al. Clinical predictors of acute respiratory acidosis during exacerbation of asthma and chronic obstructive pulmonary disease Eur J Emerg Med 2002;9(3):225-32.
  2. Emerman CL, Cydulka RK. Use of peak expiratory flow rate in emergency department evaluation of acute exacerbation of chronic obstructive pulmonary disease Ann Emerg Med 1996;27(2):159-63.