Peak expiratory flow in normals: comparison of the mini Wright versus spirometric predicted peak flows

U.S. prediction equation estimated peak flows were obtained spirometrically and may not correctly predict actual peak flows that are obtained using a peak flow meter. The purpose of this investigation was to compare actual Mini Wright peak flows in normal volunteers as compared with spirometric predicted values to determine whether they are similar.

Nonsmoking, nonobese adult volunteers with no history of lung disease underwent peak flow testing with an American Thoracic Society (ATS) Mini Wright peak flow meter. All subjects did three peak flows by taking a maximal deep breath and expiring as hard and fast as possible while in the standing position. The best of three efforts was taken as the peak flow value for analysis and compared with prediction equation estimates. The paired t test compared differences between actual and predicted values. The concordance correlation coefficient evaluated whether the actual peak flows were interchangeable with predicted.

Seventy-two volunteers, average age 44 +/- 10 years and mean BMI 25.2 +/- 2.9, were included. The Mini Wright peak flow values of 508 +/- 113 L/min were significantly different than the predicted values of 471 +/- 84 (p < 0.01). The predicted values were reduced on average by 7.3 percent compared to actual values. The concordance correlation coefficient was 0.72 (95% C.I.; 0.60 - 0.80) suggesting the actual and predicted values are not interchangeable.

The ATS Mini Wright peak flow values are slightly higher than spirometrically derived predicted peak flow values in subjects without lung disease. This suggests that predicted peak flow values should be generated by a peak flow meter and would be higher than current spirometrically predicted values.