Chest
clinical significance of pulmonary function testsSpirometry: FEV, vs FEF25-75 Percent
Section snippets
METHODS
One hundred twenty consecutive patients referred to the pulmonary function laboratory because of suspected pulmonary disease underwent spirometric testing in the sitting position using a Collins Stead-Wells spirometer. The maneuvers and analysis of the spirograms were made according to the standard methods recommended by the American Thoracic Society.3 Reference values were taken from Morris et al.4
The patients were divided into two groups. Group A consisted of 30 men (average age, 46 years ±
RESULTS
In group A, the FEF25-75% was in the normal range in all cases. In this group, the mean FEV1/FVC was 79 ± 4 percent (range 75-88). The mean FEF25-75% expressed as percent predicted was 78 ± 15 (range 54-101) and expressed in liters per second was 2.8 ± 0.64.
In group B, the mean FEF25-75% expressed as percent predicted was 27 ± 13 (range 5-50) and expressed in liters per second was 0.74 ± 0.42. The FEV/FVC was less than 75 percent in all patients except for four. The FEV/FVC was abnormally low
DISCUSSION
We confirmed the assumption of Permutt and Menkes2 that if FEV/FVC is equal or greater than 75 percent and normal, the FEF25-75% will also be normal. The only exception is in patients with lung restriction, but these are easily identified as having low FEV1 in liters, as well as reduced total lung capacity.
As a corollary, when the FEF25-75% is abnormally reduced, the FEV1/FVC always will be less than 75 percent, but not necessarily abnormal, since the latter ratio is age-dependent. Therefore,
REFERENCES (5)
- et al.
A reduction in maximum midexpiratory flow rate: A spirographic manifestation of small-airways disease
Am J Med
(1972) - Permutt S. Menkes HA. Spirometry-analysis of forced expiration within the time domain. The lung in the transition...