Predictors of outcome of noninvasive ventilation in severe COPD exacerbation

Background: Noninvasive ventilation (NIV) reduces the rate of endotracheal intubation (ETI) and overall mortality in severe acute exacerbation of COPD (AECOPD) with acute respiratory failure and is increasingly applied in respiratory intermediate care units. However, inadequate patient selection and incorrect management of NIV increase mortality. We aimed to identify factors that predict the outcome of NIV in AECOPD. Also, we looked for factors that influence ventilator settings and duration.

Methods: A prospective cohort study was undertaken in a respiratory intermediate care unit in an academic medical center between 2016 and 2017. Age, BMI, lung function, arterial pH and pCO2 at admission (t0), at 1-2 h (t1) and 4-6 h (t2) after admission, creatinine clearance, echocardiographic data (that defined left heart dysfunction), mean inspiratory pressure during the first 72 h (mIPAP-72 h) and hours of NIV during the first 72 h (dNIV-72 h) were recorded. Main outcome was NIV failure (i.e., ETI or in-hospital death). Secondary outcomes were in-hospital mortality, length of stay (LOS), duration of NIV (days), mIPAP-72 h, and dNIV-72 h.

Results: We included 89 patients (45 male, mean age 67.6 years) with AECOPD that required NIV. NIV failure was 12.4%, and in-hospital mortality was 11.2%. NIV failure was correlated with days of NIV, LOS, in-hospital mortality (p < 0.01), and kidney dysfunction (p < 0.05). In-hospital mortality was strongly associated with days of NIV (OR 1.27, 95%CI: 1.07-1.5, p < 0.01) and with FEV1 (p < 0.05). All other investigated parameters (including left heart dysfunction, dNIV-72 h, mIPAP-72 h, pH, etc.) did not influence NIV failure or mortality. dNIV-72 h and days of NIV were independent predictors of LOS (p < 0.01). Regarding the secondary outcomes, left heart dysfunction and pH at 1-2 h independently predicted NIV duration (dNIV-72 h, p < 0.01), while BMI and baseline pCO2 predicted NIV settings (mIPAP-72 h, p < 0.01).

Conclusion: In-hospital mortality and NIV failure were not influenced by BMI, left heart dysfunction, age, nor by arterial blood gas values in the first 6 h of NIV. Patients with severe acidosis and left heart dysfunction required prolonged use of NIV. BMI and pCO2 levels influence the NIV settings in AECOPD regardless of lung function.