Chest
Volume 106, Issue 5, November 1994, Pages 1419-1426
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Clinical Investigations: Asthma
Comparison Between Peak Expiratory Flow Rates (PEFR) and FEV1 in the Monitoring of Asthmatic Subjects at an Outpatient Clinic

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Peak expiratory flow rate (PEFR) monitoring is often used alone in evaluating bronchial caliber and the response to a bronchodilator in the assessment of asthmatic subjects. A 15% change in airway caliber has been proposed as the criteria for modifying treatment. Our aim was to determine if changes in PEFR from one visit to the next can adequately evaluate changes in airway caliber as assessed by FEV1, which is considered the gold standard, and to identify the characteristics of subjects whose evaluations were inadequate. This was a retrospective study of 197 asthmatic subjects seen regularly at an outpatient clinic for whom FEV1 and PEFR assessments, prebronchodilator and postbronchodilator, were available for two visits. There was a high correlation between PEFR and FEV1 (in absolute value or percent predicted) (r=0.83 and r=0.75). However, 24 of 56 (43%) of those who had a change in FEV1 of 15% or more between two visits (mean change [%]±SD, range [best-lowest/best]=20.9 ± 5.1%, 15 to 36%) showed changes in PEFR of less than 15% (6.7 ± 6.5%, 8.0 to 13.9%). On the other hand, 14 of 42 (33%) subjects with changes in FEV1 of less than 15% (9.8 ± 3.2%, 1.1 to 13.8%) had changes in PEFR of 15% or more (22.2 ± 10.9%, 16 to 35%). This discrepancy was not related to differences in baseline FEV1, control status, or the relationship between changes in FEV1 and PEFR in response to a bronchodilator. In conclusion, assessment of airway caliber through PEFR monitoring may not be valid in some asthmatic subjects and can often lead to underestimation or overestimation of changes in FEV1. None of the explanations considered made it possible to identify these subjects.

Section snippets

Subjects

Subjects were selected from a population of 303 patients who had been seen by two of us (J.L.M., A.C.) at least twice at the asthma outpatient clinic of the tertiary care Sacré-Coeur Hospital, over a 2-year period between 1990 and 1992, and for whom FEV1 and PEFR data had been collected. Entry criteria for the study group were as follows: (1) aged between 16 and 75 years; (2) a diagnosis of asthma according to American Thoracic Society (ATS) criteria;13 (3) FEV1 and PEFR measurements at each

Baseline Results

Detailed demographic, personal, and clinical characteristics are shown in Table 1. Our study population of 197 subjects had a higher proportion of women (58%) than men (42%). Very few subjects were current smokers at the time of the study. Most were atopic. Almost all of them had a diagnosis of asthma; only six (3.0%) subjects had asthma associated with chronic obstructive lung disease. Most subjects were using an inhaled β2-adrenergic agent together with an inhaled steroid, with or without

Discussion

The results of this study show that the percent change in FEV1 is more marked than the corresponding percent change in PEFR in asthmatic subjects being followed up at a respiratory outpatient clinic. The relationship between these two measurements was assessed using correlation coefficients, but since this method may be misleading,20 we also used agreement analysis and graphic techniques. As recently reviewed by Cross and Nelson,1 Lebowitz,2 and others,6, 7, 8 we found very good correlation

ACKNOWLEDGMENTS

We would like to thank the medical technologists of the Department of Chest Medicine of Sacré-Coeur Hospital for the administration and supervision of the lung function tests. We also thank Katherine Tallman for reviewing the manuscript.

References (25)

  • RosenblattG et al.

    The correlation of peak flow rate with maximal expiratory flow rate, one-second forced expiratory volume, and maximal breathing capacity.

    Am Rev Respir Dis

    (1963)
  • ConnellyCK et al.

    Relationship between different measurements of respiratory function in asthma.

    Respiration

    (1987)
  • Cited by (0)

    Dr. Gautrin is a research fellow with the Fonds de la Recherche en Sante du Quebec (Program 16.1) and with Boehringer-Ingelheim. Dr. Malo is a research fellow with the Fonds de la Recherche en Sante du Quebec and the Université de Montréal School of Medicine.

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