Analysis of the relationship between health status and mortality in hypercapnic patients with noninvasive ventilation

Health status and mortality are important outcomes in patients with advanced pulmonary diseases receiving noninvasive ventilation (NIV). However, their relationship has not been thoroughly investigated.

The present study prospectively recruited 56 stable outpatients treated with NIV for chronic hypercapnic respiratory failure caused by chronic obstructive pulmonary disease and/or pulmonary tuberculosis sequelae. At baseline, health status was measured by the Medical Outcomes Study 36-item short form, a generic questionnaire; the St. George's Respiratory Questionnaire (SGRQ), a respiratory-specific questionnaire; and two respiratory failure-specific questionnaires, the Maugeri Respiratory Failure questionnaire and the Severe Respiratory Insufficiency (SRI) questionnaire. Arterial blood gas, pulmonary function, dyspnea and psychological status were also measured.

In cross-sectional comparisons of the four health status questionnaires, the SGRQ and SRI questionnaire had lower floor and ceiling effects. During the 3-year follow-up, 16 patients (29%) died. Health status shown by the SGRQ and SRI was significantly predictive of mortality, independently of the physiological measures of low body mass index (BMI), hypercapnia, and low pulmonary function. Stepwise multivariate analyses indicated that the SRI summary score was the most significant predictor of mortality (P = 0.0006) followed by BMI (P = 0.012).

There was a significant relationship between health status and 3-year mortality in patients with NIV, independently of under-nutrition, hypercapnia and low pulmonary function. Health status measurement is important not only to comprehensively evaluate disease severity in relation to its close association with mortality, but also to elucidate factors that improve the survival of patients with advanced respiratory diseases.