Introduction: The Chronic Respiratory Disease Questionnaire (CRDQ) is a specific evaluation instrument that has been recently translated to Spanish and validated in patients with COPD without chronic respiratory insufficiency.
Objective: To study the relation of CRDQ scores to several lung function parameters in COPD patients with chronic hypoxemia (PaO2 < 65).
Material and methods: Forty-four middle aged [68 (7)] men with COPD (FEV1 post-PBD < 50%; PaO2 < 65 mmHg) were enrolled with established medical histories, including blood gas and spirometric data. We collected the patients' responses to the CRDQ and measured blood gas levels, spirometric and plethysmographic variables and DLCO. Performance on a six-minute walking test was recorded, with dyspnea assessed on a visual analogue scale (VAS) initially and at the end of the walk. Nighttime pulse oximetry was also monitored. Pearson's and Spearman's correlation coefficients were used to study the relation between CRDQ scores and the aforementioned parameters. Gas and spirometric data were compared to CRDQ scores between groups of patients treated with continuous domiciliary oxygen therapy (CDOT) and the untreated group, using Student t-test and a Mann-Whitney U-test.
Results: Results are expressed as means and standard deviations within parentheses. FVC was 2,609 (618) ml, 72 (15)%; FEV1 867 (297) ml, 34 (11)%; FEV1/FVC 33 (8)%; PaO2 55(8) mmHg; and PaCO2 49(6) mmHg. The overall CRDQ score was related to FEV1 (0.38; p < 0.01); FEV1/FVC (0.43, p < 0.005); walking test distance (0.49, p < 0.01); final VAS (-0.64, p < 0.0001) and DLCO (0.59, p < 0.01). No relation was observed between CRDQ score and blood gases, nighttime pulse oximetry or plethysmograph data. "Dyspnea", "fatigue", "emotional function" and "disease control" dimensions of the CRDQ were related to the same variables as was the overall score, with the exception of FEV1/FVC for the "fatigue" dimension and FEV1 and DLCO for the "disease control" dimension. The CRDQ scores were similar in the CDOT and non-CDOT groups in spite of differences in their spirometric and gasometric variables.
Conclusions: 1) Score on the CRDQ is related to FEV1, the FEV1/FVC ratio, walking test distance, dyspnea and DLCO but not to blood gases, FVC, lung volume or nighttime pulse oximetry. 2) The VAS dyspnea score recorded at the end of the walking test is the variable that is most strongly related to CRDQ score. 3) We found that use of CDOT did not undermine the COPD patient's quality of life.