ArticlesEffect of non-invasive positive pressure ventilation (NIPPV) on mortality in patients with acute cardiogenic pulmonary oedema: a meta-analysis
Introduction
In the past two decades, non-invasive respiratory support has received a great deal of interest in the management of patients presenting with acute cardiogenic pulmonary oedema. This non-invasive respiratory support has been provided either by continuous positive airway pressure (CPAP) or by bilevel ventilation (both inspiratory and expiratory support), which are often collectively termed as non-invasive positive pressure ventilation (NIPPV). Although CPAP is not a true ventilatory mode, it is often referred to as NIPPV. The physiological effects of CPAP include augmentation of cardiac output and oxygen delivery,1 improved functional residual capacity and respiratory mechanics, reduced effort in breathing,2 and decreased left ventricular afterload.3, 4
The combination of inspiratory assistance with expiratory positive airway pressure (EPAP) has been argued to reduce the work of breathing and to alleviate respiratory distress more effectively than CPAP alone. Physiological studies in acute cardiogenic pulmonary oedema have shown that bilevel ventilation to be more effective at unloading the respiratory muscles than CPAP.5 However, enthusiasm for bilevel ventilation in acute cardiogenic pulmonary oedema was reduced after adverse effects were recorded by Mehta and colleagues.6 These adverse effects included a higher myocardial infarction rate with bilevel ventilation than that with CPAP; this difference occurred despite more rapid reductions in arterial carbon dioxide tension (PaCO2) with bilevel ventilation than with CPAP.
Thus, the best respiratory support for treatment of an episode of acute respiratory failure due to acute cardiogenic pulmonary oedema remains unclear. The British Thoracic Society guidelines7 recommend the use of CPAP in patients who still have hypoxia despite the best medical treatment, and reserve the use of bilevel ventilation for patients in whom CPAP is unsuccessful. Subsequent to the first meta-analysis on this subject,8 several published randomised controlled trials have shown the benefits of CPAP and bilevel ventilation in reducing the need for mechanical ventilation in patients with acute cardiogenic pulmonary oedema. This meta-analysis was undertaken to assess and compare the benefits of CPAP and bilevel ventilation beyond a reduction in mechanical ventilation needs to other clinically relevant endpoints in patients with acute cardiogenic pulmonary oedema, such as mortality and length of hospital stay.
Section snippets
Trial selection
Randomised trials on acute cardiogenic pulmonary oedema in human beings that compared CPAP or bilevel ventilation with standard therapy (oxygen by facemask, diuretics, nitrates, and other supportive care) or CPAP with bilevel ventilation were considered for inclusion. Only trials reporting hospital mortality or the need for invasive mechanical ventilation were included. We excluded studies reporting only physiological endpoints (improvements in gas exchange) and descriptive studies. Our search
Results
Of the 43 160 articles on respiratory failure or insufficiency that were screened, one investigator (JVP) reviewed abstracts of the 1354 articles pertaining to respiratory support in acute cardiogenic pulmonary oedema, and three investigators (JVP, JLM, ADB) reviewed 110 articles for further assessment (table 1). 23 articles fulfilled criteria for inclusion, including three abstracts. 12 studies compared CPAP with standard therapy,21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32 seven compared
Discussion
This systematic review has shown the benefit of NIPPV in the management of patients presenting with acute cardiogenic pulmonary oedema. A significant reduction in the need for invasive mechanical ventilation was seen with both CPAP and bilevel ventilation compared with standard therapy. The mortality benefit of NIPPV reached significance for CPAP (vs standard therapy) and tended towards significance for bilevel ventilation versus standard therapy. Mortality did not differ significantly between
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