Chest
Volume 120, Issue 2, August 2001, Pages 482-488
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Clinical Investigations
Techniques
Can Peak Expiratory Flow Measurements Estimate Small Airway Function in Asthmatic Children?

https://doi.org/10.1378/chest.120.2.482Get rights and content

Background

Asthma is characterized in part by small airways dysfunction. Peak expiratory flow (PEF) measurement has been suggested by all international guidelines as an important tool in asthma management. The correlation between PEF and FEV1 but not with forced expired flow at 50% of vital capacity (FEF50) is well-established.

Study objective

To determine the value of PEF measurement as a predictor of small airways status as expressed by FEF50.

Design

Analysis of the association between PEF and FEF50 in single and multiple determinations.

Patients

One hundred eleven asthmatic children (mean age, 11.8 years), grouped in the following way according to FEV1 values: within normal range (n = 46); mildly reduced FEV1 (n = 44); and moderately/severely reduced FEV1 (n = 21).

Results

Overall, FEF50 and PEF were significantly correlated (r = 0.49; p < 0.0001). However, in 41.6% of the patients, the actual FEF50 differed by > 20% from the calculated FEF50. PEF has a high specificity (82.4%) but a poor sensitivity (51.7%) to detect FEF50 status. PEF was better able to reflect abnormal FEF50 in the patients with more severe asthma and to reflect normal FEF50 values in the healthier patients. In patients with multiple measurements (n = 40), the correlation between FEF50 and PEF was significantly better than that derived from a single determination (multiple measurements r = 0.77; single measurement, r = 0.49).

Conclusions

Although PEF is an important tool in the management of asthmatic patients, it does not yield a complete picture because it is not sensitive in detecting small airways function. It is best used at home along with regular spirometry measurements at the clinic. PEF may serve as a better index of changes in small airways function once an individual regression is determined.

Section snippets

Materials and Methods

In a retrospective study, FVC maneuvers of 111 asthmatic children were extracted from the lung function results stored in the laboratory database. The patients were selected in alphabetical order, and the first 111 patients < 18 years of age who had technically acceptable flow-volume curves were included in the study. The diagnosis of asthma was made on clinical grounds by one of the pediatric pulmonologists of the Institute of Pulmonology at Hadassah University Hospital (Jerusalem, Israel). Of

Results

The correlation between individual values of FEF50 and PEF is shown in Figure 1, top. The regression equation was: FEF50 = 0.575 × PEF +10.8 (r = 0.49; p < 0.0001). A second-order regression analysis did not yield a better correlation, and we therefore limited ourselves to linear analyses. A good correlation also was found between individual values of FEV1 and PEF, with the regression equation PEF = 0.831 × FEV1 + 17.5 (r = 0.69; p < 0.0001). The best correlation was found between individual

Discussion

A significant correlation (r = 0.49; p < 0.0001) was found between FEF50 and PEF in our asthmatic children similar to that reported in a study of healthy adults.9 However, the ability of a single determination of PEF to predict FEF50 based on this correlation was found to be limited, in that FEF50(act) deviated by > 20% in 45 of the patients (40.5%) and by > 30% in 22 of the patients (19.8%). We have further shown that repeated measurements of both parameters enabled us to establish an

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