Predictive significance of the six-minute walk distance for long-term survival in chronic hypercapnic respiratory failure

Background: The 6-min walk distance ( 6-MWD) is a global marker of functional capacity and prognosis in chronic obstructive pulmonary disease ( COPD), but less explored in other chronic respiratory diseases. Objective: To study the role of 6-MWD in chronic hypercapnic respiratory failure ( CHRF). Methods: In 424 stable patients with CHRF and non-invasive ventilation ( NIV) comprising COPD ( n = 197), restrictive diseases ( RD; n = 112) and obesity-hypoventilation- syndrome ( OHS; n = 115), the prognostic value of 6-MWD for long- term survival was assessed in relation to that of body mass index (BMI), lung function, respiratory muscle function and laboratory parameters. Results: 6-MWD was reduced in patients with COPD ( median 280 m; quartiles 204/350 m) and RD ( 290 m; 204/362 m) compared to OHS ( 360 m; 275/440 m; p <0.001 each). Overall mortality during 24.9 (13.1/40.5) months was 22.9%. In the 424 patients with CHRF, 6-MWD independently predicted mortality in addition to BMI, leukocytes and forced expiratory volume in 1 s ( p <0.05 each). In COPD, 6-MWD was strongly associated with mortality using the median {[} p <0.001, hazard ratio ( HR) = 3.75, 95% confidence interval (CI): 2.24-6.38] or quartiles as cutoff levels. In contrast, 6-MWD was only significantly associated with impaired survival in RD patients when it was reduced to 204 m or less (1st quartile; p = 0.003, HR = 3.31, 95% CI: 1.73-14.10), while in OHS 6-MWD had not any prognostic value. Conclusions: In patients with CHRF and NIV, 6-MWD was predictive for long- term survival particularly in COPD. In RD only severely reduced 6-MWD predicted mortality, while in OHS 6-MWD was relatively high and had no prognostic value. These results support a disease-specific use of 6-MWD in the routine assessment of patients with CHRF. Copyright (C) 2007 S. Karger AG, Basel

Health-related quality of life and long-term prognosis in chronic hypercapnic respiratory failure: a prospective survival analysis

<p>Abstract</p> <p>Background</p> <p>Health-related quality of life (HRQL) is considered as an important outcome parameter in patients with chronic diseases. This study aimed to assess the role of disease-specific HRQL for long-term survival in patients of different diagnoses with chronic hypercapnic respiratory failure (CHRF).</p> <p>Methods</p> <p>In a cohort of 231 stable patients (chronic obstructive pulmonary disease (COPD), n = 98; non-COPD (obesity-hypoventilation syndrome, restrictive disorders, neuromuscular disorders), n = 133) with CHRF and current home mechanical ventilation (HMV), HRQL was assessed by the disease-specific Severe Respiratory Insufficiency (SRI) questionnaire and its prognostic value was prospectively evaluated during a follow-up of 2–4 years, using univariate and multivariate regression analysis.</p> <p>Results</p> <p>HRQL was more impaired in COPD (mean ± SD SRI-summary score (SRI-SS) 52.5 ± 15.6) than non-COPD patients (67.6 ± 16.4; p < 0.001). Overall mortality during 28.9 ± 8.8 months of follow-up was 19.1% (31.6% in COPD, 9.8% in non-COPD). To identify the overall role of SRI, we first evaluated the total study population. SRI-SS and its subdomains (except attendance symptoms and sleep), as well as body mass index (BMI), leukocyte number and spirometric indices were associated with long-term survival (p < 0.01 each). Of these, SRI-SS, leukocytes and forced expiratory volume in 1 s (FEV₁) turned out to be independent predictors (p < 0.05 each). More specifically, in non-COPD patients SRI-SS and most of its subdomains, as well as leukocyte number, were related to survival (p < 0.05), whereas in patients with COPD only BMI and lung function but not SRI were predictive.</p> <p>Conclusion</p> <p>In patients with CHRF and HMV, the disease-specific SRI was an overall predictor of long-term survival in addition to established risk factors. However, the SRI predominantly beared information regarding long-term survival in non-COPD patients, while in COPD patients objective measures of the disease state were superior. This on one hand highlights the significance of HRQL in the long-term course of patients with CHRF, on the other hand it suggests that the predictive value of HRQL depends on the underlying disease.</p