Emergency medical services/original research
Effect of Out-of-Hospital Noninvasive Positive-Pressure Support Ventilation in Adult Patients With Severe Respiratory Distress: A Systematic Review and Meta-analysis

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Study objective

Noninvasive positive-pressure ventilation (NIPPV) is increasingly being used by emergency medical services (EMS) for treatment of patients in respiratory distress. The primary objective of this systematic review is to determine whether out-of-hospital NIPPV for treatment of adults with severe respiratory distress reduces inhospital mortality compared with “standard” therapy. Secondary objectives are to examine the need for invasive ventilation, hospital and ICU length of stay, and complications.

Methods

Electronic searches of MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Cumulative Index to Nursing and Allied Health Literature were conducted and reference lists of relevant articles hand searched. Randomized controlled trials comparing out-of-hospital NIPPV with standard therapy in adults (aged ≥16 years) with severe respiratory distress published in English were included. Two reviewers independently screened abstracts, assessed quality of the studies, and extracted data. Data were pooled with random-effects models and reported as risk ratios (RRs) with 95% confidence intervals (CIs) and number needed to treat (NNT).

Results

Seven randomized controlled trials were included, with a combined total of 632 patients; 313 in the standard therapy group and 319 in the NIPPV group. In patients treated with NIPPV, the pooled estimate showed a reduction in both inhospital mortality (RR 0.58; 95% CI 0.35 to 0.95; NNT=18) and need for invasive ventilation (RR 0.37; 95% CI 0.24 to 0.58; NNT=8). There was no difference in ICU or hospital length of stay.

Conclusion

Out-of-hospital administration of NIPPV appears to be an effective therapy for adult patients with severe respiratory distress.

Introduction

Severe dyspnea is a common presenting complaint to emergency medical services (EMS) providers. Dyspnea can result from a variety of conditions, including acute cardiogenic pulmonary edema, acute exacerbation of chronic obstructive pulmonary disease, acute asthma exacerbation, and pneumonia. Out-of-hospital treatment of patients in severe respiratory distress presents unique challenges. These patients often require positive-pressure ventilation, but may have factors that make invasive ventilation by intubation or insertion of a supraglottic airway device difficult. Examples of such factors include intact airway reflexes, environmental challenges, and intubation's being a low-frequency skill for most paramedics.1, 2, 3 Additionally, “standard” out-of-hospital therapy for severe dyspnea is diverse, depending on the region of the world, ranging from simple supplemental oxygen therapy to diuretic and ionotropic infusions. The approaches currently used are varied and lack evidence to support any particular practice patterns.

Editor's Capsule Summary

What is already known on this topic

Out-of-hospital providers have few options for treating severe respiratory distress.

What question this study addressed

Does out-of-hospital noninvasive positive-pressure ventilation (NIPPV) reduce mortality?

What this study adds to our knowledge

In this meta-analysis of 7 randomized controlled trials including 632 adults, NIPPV was associated with reduced mortality and a reduced need for intubation.

How this is relevant to clinical practice

This meta-analysis supports the expanded use of out-of-hospital NIPPV for severe respiratory distress in adults.

Inhospital treatment of acute cardiogenic pulmonary edema and acute exacerbation of chronic obstructive pulmonary disease with noninvasive positive-pressure ventilation (NIPPV), which includes continuous and bilevel pressure modalities, has been studied extensively.4, 5, 6, 7, 8, 9 A recent Cochrane review of 21 studies involving 1,071 adult patients with acute cardiogenic pulmonary edema reported significantly reduced inhospital mortality (risk ratio [RR] 0.6; 95% confidence interval [CI] 0.45 to 0.84) and intubation (RR 0.53; 95% CI 0.34 to 0.83) when NIPPV was compared with standard medical care.4 A second Cochrane review of 14 studies involving 758 patients with acute exacerbation of chronic obstructive pulmonary disease on the use of NIPPV showed similarly impressive results, with reductions in hospital mortality (RR 0.52; 95% CI 0.35 to 0.76) and need for intubation (RR 0.41; 95% CI 0.33 to 0.53).7

A number of commercial systems are available that allow NIPPV to be administered out-of-hospital relatively easily without large ventilators.10, 11, 12, 13 NIPPV is increasingly being used by EMS providers for the treatment of severe respiratory distress in the out-of-hospital setting.14, 15, 16, 17, 18, 19, 20, 21, 22, 23 The primary objective of our systematic review was to determine whether out-of-hospital–administered NIPPV for the treatment of adults (aged ≥16 years) with severe respiratory distress reduces inhospital mortality compared with standard therapy. Our secondary objectives included hospital length of stay, ICU length of stay, need for invasive ventilation, and complications arising from the use of NIPPV.

Section snippets

Materials and Methods

The systematic literature searches were conducted in MEDLINE (1946 to December 2012), EMBASE Classic and EMBASE (1947 to week 48, 2012), Cumulative Index to Nursing and Allied Health Literature (1982 to December 2012), and Cochrane Central Register of Controlled Trials (December 2012) by a research librarian with formal training in electronic literature searching.

Only randomized controlled trials comparing the use of out-of-hospital NIPPV with standard therapy in adults (aged ≥16 years) in

Results

Our search strategy yielded 734 potentially relevant clinical citations from multiple databases. After elimination of duplicate citations and reports that did not satisfy the selection criteria, 17 full-text articles were retrieved (Figure 1). After screening for eligibility, 7 randomized controlled trials were included in the review, with a combined total of 632 patients, 313 in the standard therapy group and 319 in the NIPPV group.14, 15, 16, 17, 18, 19, 20 The extent of agreement between

Limitations

As with any meta-analysis, the conclusions can only be as strong as the quality and consistency of trials that are included. There are a few important differences that existed between the studies included in this review.

Although our meta-analysis did not demonstrate statistically significant heterogeneity across the 7 studies included in the analysis, there is a significant amount of clinical heterogeneity warranting further discussion. The majority (>97%) of patients included in our review had

Discussion

The results of this systematic review and meta-analysis suggest that the use of out-of-hospital NIPPV reduces the risk of inhospital mortality and need for invasive ventilation compared with standard therapy for the treatment of adult patients with severe respiratory distress. The use of out-of-hospital NIPPV in patients presenting with undifferentiated dyspnea does not appear to increase complication rates.

Acute cardiogenic pulmonary edema and acute exacerbation of chronic obstructive

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    Supervising editor: Steven M. Green, MD

    Author contributions: SM, SM, AD, and ML conceived the study idea and designed the study protocol. AI performed the literature search. SM and SM independently screened the titles and abstracts, assessed the quality of the studies, and independently extracted data. SM and SM performed the statistical analysis. SM and SM drafted the study manuscript and all authors contributed substantially to its revision. The primary author SM takes responsibility for the paper as a whole.

    Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The authors have stated that no such relationships exist.

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