Outcomes of patients with acute respiratory failure of mixed aetiology treated with non-invasive ventilation in a large teaching hospital critical care unit

Introduction

Bilevel non-invasive ventilation (NIV) is an established therapy in chronic obstructive pulmonary disease (COPD) and cardiogenic pulmonary oedema but evidence for its use in other acute respiratory conditions is less robust. Reported ICU mortality after NIV treatment of pneumonia ranges between 18 and 33% [1],[2], compared with 10% in exacerbations of COPD [3]. We aimed to study the outcomes of patients with acute respiratory failure of mixed aetiology treated with NIV in our critical care unit and compare findings with those already published.

Methods

Data were collected retrospectively on patients admitted to our critical care unit with acute respiratory failure requiring NIV over a 3-year period using the Metavision electronic patient record system. Patients with a primary surgical problem and those who received continuous positive airway pressure as a primary intervention were excluded. We recorded: primary respiratory diagnosis causing respiratory failure; patient demographics; serial arterial blood gas results; success of NIV as defined by the British Thoracic Society (BTS) [4]; and mortality statistics.

Results

In total, 113 consecutive patients were identified. Mean age was 64 and 50% (56/113) were male. The primary diagnosis was pneumonia in 55 patients and exacerbation of COPD in 40 patients. The overall mortality on critical care, in hospital and at 1 year was 19% (22/113), 34% (38/113) and 41% (46/113) respectively. Success of NIV as defined by BTS criteria (pH >7.3 or reduction in PaCO₂ by 0.5 kPa) in the first 6 hours was seen in 72% (80/111) of patients. In NIV responders, 1-year mortality was 31% (25/80) compared with 65% (20/31) in nonresponders.

Conclusion

NIV is used to treat acute respiratory failure due to a wide range of aetiologies in our unit with comparable mortality rates to large published series [1],[2],[5]. A successful response to NIV in the first 6 hours is associated with a reduction in 1-year mortality when compared with nonresponders.