Comparison of PEFR and FEV1 in Patients with Varying Degrees of Airway Obstruction: Discussion
For example, of 18 patients with JPF values in the range of 80 to 89 percent predicted, 11 had FEV, values of less than 70 percent predicted. The same results were observed when peak flow obtained with the WPF was used for comparison. fully
We further sought to assess the effect of altitude on values of FEV! and PEFR. The results obtained in an atmospheric chamber are summarized in Figure 4. Compared with values obtained at sea level, the mean percent predicted peak flow value for the nine normal subjects increased by 6.3 percent (range, 2 to 16 percent) at 1,515 m and 12.0 percent (range, 1 to 20 percent) at 2,272 m. No significant change in FVC or FEV! was seen at any of the altitudes tested when compared with values obtained at sea level. The increase in PEFR at 1,515 and 2,272 m was statistically significant (p<0.001, ANOVA). The peak flow values at 757.5 m also tended to be higher than FEVi and FVC, but the differences did not achieve statistical significance.
In this study, FEVj and PEFR measurements were obtained in 102 patients with possible pulmonary impairment. These parameters were selected because they are widely available, easily obtained, and commonly used. Since clinical decisions are often based on the results of these tests, we sought to compare their utility in defining the degree of pulmonary impairment on initial evaluation.
A good correlation was observed between FEV, and PEFR throughout the range of pulmonary function measured, particularly when the best value obtained for each parameter was utilized rather than the mean values. The peak flow obtained with the WPF provided as good an estimate of peak flow as was attainable with a spirometer, a finding in keeping with previous reports. In fact, the PEFR measurements obtained by the WPF provided a comparable correlation with FEV, to that obtained by the JPF and demonstrated less intrasubject variability. Peak flow values obtained with either the JPF or the WPF appeared to minimize the degree of pulmonary obstruction. Patients were routinely able to generate higher percent predicted peak flows, even in the face of diminished FEV, values.
Figure 4. Percent predicted change observed at simulated altitudes compared with sea level.