Asthma: acute exacerbation: PEFR could predict problems as well as FEV1.

Clinical bottom line (level 4)

  1. Both PEFR (< 100 l/min pre-treatment, < 300 l/min post-treatment) and FEV1 (< 0.7 l/min pre-treatment, < 2.1 l/min post-treatment) could predict which patients will require admission or have continuing symptoms.
Nowak et al: Annals of Emergency Medicine 1982; 11: 64-69
Expires November 2002

The study

Inception cohort study with unblinded, unobjective outcomes, not adjusted for confounding factors, not validated in an independent set of patients.

Setting: emergency department, university hospital, USA

90 patients (aged mean 25 years, 62% female) with 109 episodes of acute asthma (acute bronchospasm and acute respiratory distress)

Excluded if
  • <16 or >40 years old
  • other cardiac or respiratory disease



    • Factors studied:
  • admission
  • pre-treatment PEFR <100 l/min
  • pre-treatment FEV1 <0.7
  • post-treatment PEFR <300 l/min
  • post-treatment FEV1 <2.1 l/min


    • All patients had terbutaline 0.25 mg s/c and iv aminophylline 5.6 mg/kg loading dose, followed by 0.9 mg/kg/hour.

    ?100% followed for 48 hours
    Outcomes studied:
  • admission admission (based on FEV1 and clinical findings) or failed discharge; if answered yes to two or more of: worsening asthma; re attendance at emergency department/ seen another doctor; asthma keeping patient awake at night; unable to resume usual activities

    • The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)
    admission 48 hours / 75%
    (% to %)

    prognostic factor for
    admission     		time to outcome unadjusted RR
    (95% CI)    		 NNF+
    (95% CI)
    pre-treatment PEFR <100 l/min 48 hours 1.86
    (1.32 to 2.61)     		3
    (2 to 8)
    pre-treatment FEV1 <0.7 48 hours 2.69
    (1.74 to 4.16)     		2
    (1 to 5)
    post-treatment PEFR <300 l/min 48 hours 5.43
    (2.55 to 11.6)     		2
    (1 to 5)
    post-treatment FEV1 <2.1 l/min 48 hours 4.19
    (1.97 to 8.90)     		2
    (1 to 6)

    Comments

    1. There was significant confounding between decision to admit and FEV1 (since this was used as one of the admission criteria).
    2. Peak expiratory flow meters are cheaper, easier to use and more portable than spirometers.

    Citation

    1. Nowak RM, Pensler MI, Sarkar DD, et al: comparison of peak expiratory flow and FEV1 admission criteria for acute bronchial asthma. Annals of Emergency Medicine 1982; 11: 64-69
    Search Terms: reference from acute asthma chapter; Lee, Hsu, Stasior; Quick consult manual to evidence-based medicine: publ. Lippincott-Raven, 1997
    Contributor: Chris Ball and Clare Wotton, November 2000
    Reviewer: Mitsuhiro Kamei

    Clinical Question.
    Patient acute asthma
    Intervention or Exposure PEFR
    Comparison FEV1
    Outcome predicting admission.