Measurement of the FEV1 and PEFR in COPD patients is a significant indicator of the disease severity , the response to treatment and the acute exacerbation. However, it is not known if PEFR can be used to determine the severity of COPD because the agreement between PEFR and FEV₁ in COPD patients is not well known.

From September, 2003 to August, 2004, 125 out patients with COPD who were treated at the pulmonary clinic in KonKuk University Hospital were enrolled in this study. The FEV₁ and PEFR of each patient were measured and all the data was analyzed using SPSS.

The average predicted FEV1 % and PEFR % was 56.98 ± 18.21% and 70 ± 27.60%, respectively. There was linear correlation between the predicted FEV1 % and predicted PEFR %. There was no correlation between age of the COPD patients and the predicted PEFR %. There was correlation between dyspnea, which is a subjective symptom of the patients, and the predicted PEFR %.

In COPD patients, the classification of the severity by PEFR tends to underestimate the state of the disease compared with the classification of the severity by the FEV₁. Therefore, the classification of the severity by PEFR should be interpreted carefully in patients with severe symptoms. Once the classification of the severity has made, the follow-up examination may use the PEFR instead of the FEV₁.