Intended for healthcare professionals

Editorials

Non-invasive ventilation in chronic obstructive pulmonary disease

BMJ 2003; 326 doi: https://doi.org/10.1136/bmj.326.7382.177 (Published 25 January 2003) Cite this as: BMJ 2003;326:177

Effective in exacerbations with hypercapnic respiratory failure

  1. K Suresh Babu, research fellow,
  2. Anoop J Chauhan, consultant physician
  1. Inflammation, Repair, and Cell Biology Division, Southampton General Hospital, Southampton SO16 6YD
  2. St Mary's Hospital, Portsmouth PO3 6AD

    Papers p 185

    Chronic obstructive pulmonary disease is a leading cause of global morbidity and mortality, and about 15% of adults in industrialised countries have chronic obstructive pulmonary disease when defined by spirometry. Mild exacerbations are common, and the development of hospital at home services for acute exacerbations has improved the treatment options for managing mild exacerbations safely in the community. Severe exacerbations, however, remain the largest single cause of emergency admissions for respiratory disease (far higher than for asthma), with a mean hospital stay of around 10 days. According to hospital episode statistics from the Department of Health, exacerbations of chronic obstructive pulmonary disease resulted in 135 000 admissions and just under a million bed days in England in 2000–1 (www.doh.gov.uk/hes). These account for over a third of the overall healthcare costs associated with treating chronic obstructive pulmonary disease in the United Kingdom. Exacerbations are not only expensive but can impair lung function and quality of life and are associated with further readmissions.

    Severe exacerbations with impaired gas exchange are associated with death rates of up to 14%.1 In particular, admission to an intensive care unit and acute hypercapnic respiratory failure are associated with higher death rates—up to 59% at one year.2 Non-invasive ventilation is now recognised as an important tool in the treatment of acute hypercapnic respiratory failure associated with exacerbations of chronic obstructive pulmonary disease. The procedure provides ventilatory support to the upper airway by using facial or nasal devices, can avoid the morbidity and mortality associated with tracheal intubation, and is useful for patients in whom invasive intervention is considered inappropriate.

    A series of randomised trials of non-invasive ventilation in acute exacerbations of chronic obstructive pulmonary disease has been performed, but in different ward settings. In the intensive care unit, non-invasive ventilation has shown significant reductions in tracheal intubation rates but not in overall mortality. 3 4 Studies conducted outside intensive care units have also shown inconsistent results, some of which can be explained by differences in the severity of exacerbations5 and study design, such as comparison with historical controls.6 The largest randomised controlled trial showed significantly reduced failure of treatment (a proxy for rate of intubation) from 27% to 15% and reduced short term mortality from 20% to 10%.7 The issue of including all patients unable to tolerate non-invasive ventilation or those requiring immediate tracheal intubation is important. Many of the randomised trials have excluded patients who were deemed severe enough at the outset to require immediate intubation and ventilation. Further differences between studies arise as a result of heterogeneity of non-invasive ventilation treatment protocols with varied levels of inspiratory pressure support, duration of treatment, and disparity of face and nasal masks.

    The recent publication of the British Thoracic Society's guidelines on non-invasive ventilation has provided a summary of the evidence for the technique in acute respiratory failure, and recommendations on standards of care required for a non-invasive ventilation service.8 Several factors predict the success of non-invasive ventilation in acute respiratory failure, including a satisfactory interface between patient and mask, a rapid improvement in pH, and less severe physiological and chronic derangement of patients' health at the outset of treatment. Some uncertainties remain concerning factors that determine the success of non-invasive ventilation, such as the optimum treatment protocol, severity of acidosis at admission versus location of study (intensive care and non-intensive care unit settings),7 and whether an overall benefit in mortality exists that avoids selection bias by including patients on an intention to treat basis. Bott et al showed no difference in an intention to treat analysis, but a survival benefit in the group receiving non-invasive ventilation after excluding patients unable to tolerate non-invasive ventilation.9

    In this issue, Lightowler et al report the results of a meta-analysis of eight trials of non-invasive ventilation in exacerbations of chronic obstructive pulmonary disease compared with standard care, conducted by the Cochrane Collaboration10 (see p 185). Further information was available from the authors of five of the included trials, and seven trials were presented by using intention to treat analyses. Significant risk reductions were observed in patients treated with non-invasive ventilation for mortality (59%, number needed to treat 8), treatment failure (49%, NNT=5), intubation (58%, NNT=5), treatment complications (68%, NNT=3), and length of stay in hospital reduced by three days. These risk reductions are higher than those reported in another meta-analysis.11 Although differences in risk reductions were observed between subgroup analyses for pH (<7.30, or between 7.35-7.30) and location (intensive care unit v non-intensive care unit settings), most were not significant.

    The overall findings confirm the efficacy of non-invasive ventilation outside the intensive care unit setting if conducted in an appropriately equipped and supervised environment, but it does not identify whether patients categorised by baseline pH or location are more likely to benefit. Further evidence is needed before this can be ascertained. In some categories of patients, non-invasive ventilation remains unproved largely as a result of exclusion from the controlled trials (for example, pneumonia, copious respiratory secretions, and comorbidity). Respiratory tract infections are the commonest identifiable cause of exacerbations of chronic obstructive pulmonary disease, and the prevalence of other illnesses such as coronary artery disease is often high. Coronary artery disease and chronic obstructive pulmonary disease share tobacco abuse as a risk factor; it is therefore not surprising that these two disorders commonly coexist in up to 50% of cases.12 Future studies need to address the benefits of non-invasive ventilation in these subgroups.

    Information from the Centres for Evidence based Medicine (www.nelh.nhs.uk/eboc) and the Cochrane Library confirm that standard therapy for exacerbations of chronic obstructive pulmonary disease show significant risk reductions for an improvement in symptoms with oxygen (61%) and theophyllines (OR=2.46),13 improved recovery and reduced length of stay with antibiotics (29%), and reduced treatment failure with systemic corticosteroids (31%).14 The efficacy of non-invasive ventilation compares favourably, and it provides a window of opportunity for intervention during exacerbations. Patients with mild exacerbations will improve with standard care5 but the timely use of non-invasive ventilation in more severe exacerbations will improve outcome and reduce mortality.10

    Footnotes

    • Competing interests None declared.

    References

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