Correlation of the quality of life with the inspiratory capacity in patients with chronic obstructive pulmonary disease

Abstract

To evaluate the correlation of the quality of life in patients with chronic obstructive pulmonary disease (COPD) with the lung function tests, especially the inspiratory capacity (IC). Sixty-two stable COPD patients were enrolled between Jan. 2006 and Mar. 2007 (55 males and 7 females), with an age range of 43 - 79 (66 +/- 8) years. Lung volume, spirometry and small airway function measurements were performed in all patients. The St George respiratory questionnaire (SGRQ) score was collected. Pearson's correlation coefficients were calculated. The total score of the 62 COPD patients was 43 +/- 17. The 3 component scores were: symptoms (54 +/- 23), activity (54 +/- 19) and impact (33 +/- 20). The FEV(1) pred% was (43 +/- 13)%, FEV(1)/FVC was (52 +/- 11)%, residual volume (RV) pred% was (194 +/- 50)%, RV/total lung capacity (TLC) was (166 +/- 31)%, and IC pred% was (74 +/- 21)%. The SGRQ scores were significantly correlated with IC pred%, RV pred%, RV/TLC, FEV(1) pred%, FEV(1)/FVC and small airway function measurements (FEF(50%), FEF(25%), MMEF). The correlation coefficients between the parameters of spirometry and the total score of SGRQ were -0.336 to -0.479, while those between the parameter of small airway function and the total score of SGRQ were -0.368 to -0.411. Among all these lung function measurements, IC pred% was best correlated with the SGRQ score, and the correlation coefficients between the IC pred% and the total score and the other 3 component scores of SGRQ were -0.418 to -0.521, respectively, P < 0.05. The symptoms section score had the poorest correlation with the lung function test. The lung function test results correlate with the quality of life in patients with COPD. IC pred%, together with FEV(1) pred% should be used for clinical evaluation of patients with COPD.