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Original article
Acidosis, non-invasive ventilation and mortality in hospitalised COPD exacerbations
  1. C M Roberts1,2,
  2. R A Stone1,3,
  3. R J Buckingham1,
  4. N A Pursey1,
  5. D Lowe1 On behalf of the National Chronic Obstructive Pulmonary Disease Resources and Outcomes Project (NCROP) implementation group
  1. 1Clinical Effectiveness and Evaluation unit, Royal College of Physicians, London, UK
  2. 2Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
  3. 3Taunton and Somerset NHS Trust, Musgrove Park Hospital, Taunton, UK
  1. Correspondence to Professor C M Roberts, Clinical Effectiveness and Evaluation unit, Royal College of Physicians, London, 11 St Andrews Place, Regent's Park, London NW1 4LE, UK; c.m.roberts{at}


Background Reports of non-invasive ventilation (NIV) use in clinical practice reveal higher mortality rates than in corresponding randomised clinical trials.

Aim To explore factors related to chronic obstructive pulmonary disease (COPD) admissions and NIV use that may explain some of the previously reported high mortality rates.

Methods National UK audit of clinical care of consecutive COPD admissions from March to May 2008. Retrospective case note audit with prospective case ascertainment. Participating units completed a web-based audit proforma of process and outcomes of clinical care.

Results 232 hospital units collected data on 9716 patients, mean age 73, 50% male. 1678 (20%) of those with gases recorded on admission were acidotic and another 6% became acidotic later. 1077 patients received NIV, 55% had a pH<7.26 and 49% (305/618) had or were still receiving high flow oxygen. 30% (136/453) patients with persisting respiratory acidosis did not receive NIV while 11% (15/131) of acidotic admissions had a pure metabolic acidosis and did. Hospital mortality was 25% (270/1077) for patients receiving NIV but 39% (86/219) for those with late onset acidosis and was higher in all acidotic groups receiving NIV than those treated without. Only 4% of patients receiving NIV who died had invasive mechanical ventilation.

Conclusions COPD admissions treated with NIV in usual clinical practice were severely ill, many with mixed metabolic acidosis. Some eligible patients failed to receive NIV, others received it inappropriately. NIV appears to be often used as a ceiling of treatment including patient groups in whom efficacy of NIV is uncertain. The audit raises concerns that challenge the respiratory community to lead appropriate clinical improvements across the acute sector.

  • NIV
  • COPD
  • audit
  • respiratory failure
  • COPD exacerbations
  • non-invasive ventilation
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  • Funding This study was supported by the British Lung Foundation, British Thoracic Society, Royal College of Physicians and guided by the National COPD Resources and Outcomes Project steering group. It was funded by the Health Foundation.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the Joint UCL/UCLH Research Ethics Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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