The Shape of the Maximum Expiratory Flow Volume Curve

doi:10.1378/chest.94.4.799

Chest

Volume 94, Issue 4, October 1988, Pages 799-806

https://doi.org/10.1378/chest.94.4.799 Get rights and content

Differences in the shape of the maximum expiratory flow volume (MEFV) curve have been associated with pathologic states and physiologic differences between normal individuals. We describe variations in a new parameter, angle p, which characterizes the general configuration of the MEFV curve among healthy subjects and subjects with disease in 5,140 white individuals. Women had consistently larger β angles than men. There was a progressive decline in β with advancing age. Cigarette smokers had lower β angles than did lifetime never-smokers. Subjects with abnormal lung (unction patterns had lower β angles than individuals with a normal pattern. Finally, individuals with asthma, chronic bronchitis, dyspnea and wheezing had significantly lower β angles than healthy individuals. Further clinical and epidemiologic studies are needed to evaluate this measurement's possible value in pulmonary function evaluation. (Chest 1988; 94:799-806)

Section snippets

METHODS

A cross-sectional study of the residents in three communities, Lebanon and Ansonia, Connecticut, and Winnsboro, South Carolina, was undertaken from 1972 to 1974. In each town, all persons ages seven years and older who lived in a geographically defined area were eligible to participate. Surveys were conducted in a standardized manner in a mobile van equipped with computer facilities for recording answers to a questionnaire on respiratory health, and for computing the results of pulmonary

RESULTS

Table 1 describes the distribution of the 2,382 males and 2,758 females in the study by age, by smoking status, by lung function pattern, and by presence of lung disease and symptoms.

Values for β ranged from 137.9 degrees to 255.8 degrees, with an overall mean value of 199.6 ± 18.9 (mean ± SD). Table 2 shows the mean β for the population by sex, age and smoking status. Controlling for age and cigarette smoking, females have a pattern of larger β angles than males. Controlling for sex and

DISCUSSION

We have shown for the first time that a simple parameter, angle P, related to the shape of the MEFV curve is useful in explaining previous characterizations of the shape of MEFV.

As with other lung function parameters, we have shown that β is different for men and women, with female subjects having larger mean values of β than male. This sex difference is not eliminated when controlling for other factors influencing β such as smoking history and age. Similarly, β is seen to change with age,

APPENDIX

The angle formed by connecting the projection of the peak flow point on the y-axis to the mid-flow point ( $\dot{V}$ max50%) and that point to the residual volume point is designated β (Fig 1). The angles β? and β? as illustrated in the figure are related to β by the formula

$β = 180^{ˆ} - β^{'} + β^{″}$

The relationship between β? and flows measured on the MEFV curve is given by the formula

$\tan (β^{'}) = \frac{PEFR - V ˙ \max 50 %}{1 / 2 FVC}$

Similarly, $\tan (β^{″}) = \frac{V ˙ \max 50 %}{1 / 2 FVC}$

From (2) and (3) it follows that $β^{'} = \tan^{- 1} (P E F R - V ˙ max50%)$

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To ensure that this did not affect our results, we averaged 30 specific points in 2% increments from each MEFV curve and found no difference in any outcome parameter. The β° was defined by connecting three points on (or near) a MEFV curve (Fig. 1) (Kapp et al., 1988). Point A is located at the intersection of coordinates for FVC on the x-axis and peak expiratory flow on the y-axis.
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This study was supported by contract J-9-M-0168 from the US Department of Labor and Grant 5R01 HL 213512, NHL BI.

Manuscript received Jan~ 11; revision accepted March 8.

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Chest

The Shape of the Maximum Expiratory Flow Volume Curve

Section snippets

METHODS

RESULTS

DISCUSSION

APPENDIX

Dis Chest

Am J Med

Respir Physiol

Am J Med

The role of respiratory dynamic compression in upper airway obstruction

Am Rev Respir Dis

The detection of sleep apnea in the awake patient: The 'saw tooth' sign

JAMA

Analysis of the configuration of maximum expiratory flow-volume curves

J Appl Physiol

Epidemiology of environmental lung disease

Yale J Biol Med

Community studies of lung disease in Connecticut: organization and methods

Am J Epidemiol

The pattern of lung function abnormalities in cotton textile workers

Am Rev Respir Dis

A prospective study of chronic lung disease in cotton textile workers

Ann Intern Med