PULMONARY-FUNCTION THRESHOLD FOR DISTINGUISHING VENTILATORY-LIMITED AND NONVENTILATORY-LIMITED PATIENTS WITH AIR-FLOW OBSTRUCTION

Patients with chronic obstructive pulmonary disease (COPD) may demonst rate great variability between results on the pulmonary function test (PFT) compared to those on the cardiopulmonary exercise test (CPXT). T he purpose of this study was to correlate PFT and CPXT indices and to identify PFT threshold values for predicting exercise capacity in pati ents with airflow limitation. Fifty-seven patients (48 men and 9 women ) of mean age 66.4 +/- 4.8 years with COPD and 40 age-matched control patients underwent PFT and CPXT. Based on the CPXT results, the patien ts were divided into ventilatory-limited (VL) and nonventilatory-limit ed (NVL), and the findings were correlated with the PFT indices. Linea r regression analysis was used to determine the relationship between d yspnea index (VEmax/MVV) and forced expiratory volume in one second (F EV1). The cutoff value for VL was FEV1 <38% and for NVL-FEV1 >68%. The prominent limiting symptom (61%) in the VL group was dyspnea sensatio n, with leg discomfort presenting in only 14%; corresponding rates in the NVL group were 38% and 31%. We conclude that the FEV1 is a reliabl e index for distinguishing VL from NVL COPD patients during CPXT at tw o extremes: below 38% of the predicted value (VL) and above 68% of the predicted value (NVL).