Weak cough is associated with increased mortality in COPD patients with scheduled extubation: a two-year follow-up study

Background Cough strength is associated with short-term outcome in patients with scheduled extubation who successfully complete a spontaneous breathing trial (SBT). However, the long-term outcome is unclear. Methods This was a prospective observational study performed in a respiratory ICU of a teaching hospital. COPD patients who successfully completed a SBT were candidates. We enrolled the case who assessed the cough strength by cough peak flow (CPF) or semiquantitative cough strength score (SCSS, ranging from 0 = weak to 5 = strong). Patients were followed up to two years by phone every 3 months. Results A total of 215 patients were enrolled in current study. Among them, CPF and SCSS were measured in 214 and 208 cases, respectively. Strong cough was associated with a 16% decrease in the risk of two-year mortality (adjusted hazard ratio [HR] 0.84, 95%CI: 0.78-0.91) per 10 L/min increment of CPF. When it was tested by SCSS, decrease in the risk of two-year mortality per unit increment was 27% (adjusted HR 0.73, 95%CI: 0.62-0.86). Similar results were confirmed in the discharged patients. In all patients, the two-year mortality was 75%, 53%, and 38% in patients with CPF < 60, 60-90, and > 90 L/min; and 85%, 70%, and 40% in patients with SCSS of 0-1, 2-3, and 4-5, respectively. Similar trend was found among the discharged patients whether it was assessed by CPF or SCSS. Conclusions In COPD patients, weak cough is associated with increased two-year mortality after a scheduled extubation. It provides objective information to caregivers to improve decision-making process during hospitalization and after discharge.