Peak expiratory flow rate

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The peak expiratory flow rate is the "measurement of the maximum rate of airflow attained during a forced vital capacity determination. Common abbreviations are PEFR and PFR."[1]

Ability to diagnose obstructive airways disease

Two studies found that the PEFR significantly added to the history and physical in helping doctors diagnose obstructive airways disease.[2][3] However, in one of the two studies the PEFR helped detect mild[2], but not moderate[4] disease.

The PEFR correlates, albeit imperfectly, with the FEV1.[5][6]

Ability to predict need for hospitalization in patients with acute asthma attacks

Clinical practice guidelines by the U.S. National Asthma Education and Prevention Program recommend:[7]

  • "Reinstates, for use in the urgent or emergency care setting, the 1991 cut points of forced expiratory volume in 1 second (FEV1) or peak expiratory flow (PEF) to indicate the goal for discharge from the urgent care or emergency care setting (≥70 percent predicted FEV1 or PEF); patients for whom response to therapy is incomplete and who usually require continued treatment in the ED (40–69 percent predicted); and the exacerbation severity level where adjunct therapies may be considered (<40 percent predicted). These cut points differ from those used to determine long-term asthma control and treatments, thus underscoring the distinction between acute and chronic asthma management."
  • "Acknowledges the limited value of pulmonary function measures in very severe exacerbations."

Regarding when to discharge a patient from the emergence room, the U.S. National Asthma Education and Prevention Program states "in general, discharge is appropriate if FEV1 or PEF has returned to ≥70 percent of predicted or personal best and symptoms are minimal or absent."[7]

Supporting evidence

Some studies find that measurement of the PEFR can help identify patients in the emergency room who will need to be hospitalized.[8][9]

Effectiveness in long-term monitoring patients with obstructive airways disease

Clinical practice guidelines

Clinical practice guidelines by the U.S. National Asthma Education and Prevention Program recommends:[7] Consider home peak flow monitoring during exacerbations of asthma for:

  • "Patients who have a history of severe exacerbations"
  • "Patients who have moderate or severe persistent asthma"
  • "Patients who have difficulty perceiving signs of worsening asthma"

Supporting evidence

In randomized controlled trials of adult patients, the role of the PEFR compared to instructing patients in how to monitor the symptoms of their lung disease is not clear with some studies reporting benefit[10][11][12] and others not finding benefit[13][14][15]. The specific advice given to the patient based on their PEFR may be important.[11] According to a meta-analysis of randomized controlled trials by the Cochrane Collaboration, peak flow monitoring is equivalent to symptom monitoring.[16]

Among children, some[17][18] but not all[19] children seem to benefit from PEFR monitoring.

Preoperative evaluation

For more information, see: preoperative care.

Clinical practice guidelines by the U.S. National Asthma Education and Prevention Program recommends:[7]

  • "Patients who have asthma should have an evaluation before surgery that includes a review of symptoms, medication use (particularly the use of oral systemic corticosteroids for longer than 2 weeks in the past 6 months), and measurement of pulmonary function".
  • "If possible, attempts should be made to improve lung function preoperatively (FEV1 or peak expiratory flow rate [PEFR]) to either their predicted values or their personal best level. A short course of oral systemic corticosteroids may be necessary to optimize lung function".

References

  1. ↑ Anonymous. Peak expiratory flow rate. National Library of Medicine. Retrieved on 2008-01-23.
  2. ↑ 2.0 2.1 Badgett RG, Tanaka DJ, Hunt DK, et al (1994). "The clinical evaluation for diagnosing obstructive airways disease in high-risk patients". Chest 106 (5): 1427–31. PMID 7956395. [e]
  3. ↑ Holleman DR, Simel DL, Goldberg JS (1993). "Diagnosis of obstructive airways disease from the clinical examination". J Gen Intern Med 8 (2): 63–8. PMID 8441077. [e]
  4. ↑ Badgett RG, Tanaka DJ, Hunt DK, et al (1993). "Can moderate chronic obstructive pulmonary disease be diagnosed by historical and physical findings alone?". Am. J. Med. 94 (2): 188–96. PMID 8430714. [e]
  5. ↑ Aggarwal AN, Gupta D, Jindal SK (2006). "The relationship between FEV1 and peak expiratory flow in patients with airways obstruction is poor.". Chest 130 (5): 1454-61. DOI:10.1378/chest.130.5.1454. PMID 17099024. Research Blogging.
  6. ↑ Llewellin P, Sawyer G, Lewis S, Cheng S, Weatherall M, Fitzharris P et al. (2002). "The relationship between FEV1 and PEF in the assessment of the severity of airways obstruction.". Respirology 7 (4): 333-7. PMID 12421241. [e]
  7. ↑ 7.0 7.1 7.2 7.3 NHLBI, Diagnosis and Management of Asthma. National Heart, Lung, Blood Institute. Retrieved on 2008-01-24. Cite error: Invalid <ref> tag; name "NAEP" defined multiple times with different content
  8. ↑ Fischl MA, Pitchenik A, Gardner LB (1981). "An index predicting relapse and need for hospitalization in patients with acute bronchial asthma". N. Engl. J. Med. 305 (14): 783–9. PMID 7266631. [e]
  9. ↑ Rodrigo G, Rodrigo C (1997). "A new index for early prediction of hospitalization in patients with acute asthma". Am J Emerg Med 15 (1): 8–13. PMID 9002561. [e]
  10. ↑ Weinberger M, Murray MD, Marrero DG, et al (2002). "Effectiveness of pharmacist care for patients with reactive airways disease: a randomized controlled trial". JAMA 288 (13): 1594–602. PMID 12350190. [e]
  11. ↑ 11.0 11.1 Gibson PG, Wlodarczyk J, Hensley MJ, Murree-Allen K, Olson LG, Saltos N (1995). "Using quality-control analysis of peak expiratory flow recordings to guide therapy for asthma". Ann. Intern. Med. 123 (7): 488–92. PMID 7661491. [e] Cite error: Invalid <ref> tag; name "pmid7661491" defined multiple times with different content
  12. ↑ Cowie RL, Revitt SG, Underwood MF, Field SK (1997). "The effect of a peak flow-based action plan in the prevention of exacerbations of asthma". Chest 112 (6): 1534–8. PMID 9404750. [e]
  13. ↑ Turner MO, Taylor D, Bennett R, Fitzgerald JM (1998). "A randomized trial comparing peak expiratory flow and symptom self-management plans for patients with asthma attending a primary care clinic". Am. J. Respir. Crit. Care Med. 157 (2): 540–6. PMID 9476870. [e]
  14. ↑ Buist AS, Vollmer WM, Wilson SR, Frazier EA, Hayward AD (2006). "A randomized clinical trial of peak flow versus symptom monitoring in older adults with asthma". Am. J. Respir. Crit. Care Med. 174 (10): 1077–87. DOI:10.1164/rccm.200510-1606OC. PMID 16931634. Research Blogging.
  15. ↑ Adams RJ, Boath K, Homan S, Campbell DA, Ruffin RE (2001). "A randomized trial of peak-flow and symptom-based action plans in adults with moderate-to-severe asthma". Respirology 6 (4): 297–304. PMID 11844120. [e]
  16. ↑ Powell H, Gibson PG (2003). "Options for self-management education for adults with asthma". Cochrane Database Syst Rev (1): CD004107. PMID 12535511. [e]
  17. ↑ Burkhart PV, Rayens MK, Revelette WR, Ohlmann A (2007). "Improved health outcomes with peak flow monitoring for children with asthma". J Asthma 44 (2): 137–42. DOI:10.1080/02770900601182517. PMID 17454329. Research Blogging.
  18. ↑ Yoos HL, Kitzman H, McMullen A, Henderson C, Sidora K (2002). "Symptom monitoring in childhood asthma: a randomized clinical trial comparing peak expiratory flow rate with symptom monitoring". Ann. Allergy Asthma Immunol. 88 (3): 283–91. PMID 11926622. [e]
  19. ↑ Wensley D, Silverman M (2004). "Peak flow monitoring for guided self-management in childhood asthma: a randomized controlled trial". Am. J. Respir. Crit. Care Med. 170 (6): 606–12. DOI:10.1164/rccm.200307-1025OC. PMID 15184205. Research Blogging.

See also

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