Acute dyspnea is a common Emergency Department complaint; in 2003 this chief complaint comprised about 3.5% of more than 115 million emergency department visits nationwide. A subset of these patients will present in respiratory distress, which is associated with increased morbidity and mortality. Often it can be hard to determine the exact etiology of the shortness of breath in a timely fashion, and therapeutic interventions need to begin before the exact diagnosis is known.

A number of studies have shown that acute cardiogenic pulmonary edema, chronic obstructive pulmonary disease and asthma exacerbations all benefit from non-invasive positive pressure ventilation (NIPPV). Cochrane systematic reviews in 2004 (Ram 2004) and in 2013 (Vital 2013) demonstrated decreased mortality in patients with obstructive pulmonary disease exacerbations and cardiogenic pulmonary edema respectively. But what about in the undifferentiated, prehospital patient with dyspnea?

Clinical Question

Does out-of-hospital NIPPV improves in-hospital mortality compared to standard treatment in patients with grossly undifferentiated respiratory distress?


Seven RCTs of adult patients (n=632) with out-of-hospital severe respiratory distress (suspected acute cardiogenic pulmonary edema, acute exacerbation of COPD, acute asthma exacerbation or pneumonia)




Standard pre-hospital care


Primary: In-hospital mortality
Secondary: Need for invasive ventilation, hospital and ICU length of stay and complications from NIV


Systematic review and meta-analysis


Studies with: patients < 16 years of age and patients without severe respiratory distress. Each study had its own exclusion criteria that were not detailed in this article.

Primary Results

  • Seven studies included in this analysis – 6 studies employed CPAP, 1 employed BPAP
  • > 80% of patients were suspected of having acute cardiogenic pulmonary edema
  • In-hospital Mortality: RR 0.58 (CI 0.35 – 0.95) NNT = 18

Additional Results

  • Need for invasive ventilation: RR 0.37 (CI 0.24 – 0.58) NNT = 8
  • Complications: 3 patients with emesis


  • Significant reduction (NNT = 18) on patient centered outcome (death)
  • Five studies judged to be at low risk of bias
  • Allocation concealed in five of the studies
  • Excellent follow up: 98.8% (624/632)


  • None of included studies were blinded
  • Majority of patients with cardiogenic pulmonary edema makes less generalizable to undifferentiated respiratory distress.
  • 6 out of 7 studies performed in Europe, which has a very different pre-hospital system to that in North America.
  • “Standard” therapy not well defined
  • Only 5 studies commented on complications

Author's Conclusions

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

Our Conclusions

We agree that NIPPV is safe and beneficial in the appropriate clinical setting. However we have yet to clearly demonstrate the ability for all-comer EMS providers to recognize these appropriate clinical scenarios. Further studies with the broader inclusion criteria of truly undifferentiated dyspnea using a clearer spectrum of EMS providers may provide more clarity on this and help bring to light any unseen adverse events which previous studies had not been powered to do.

Potential Impact To Current Practice

This article argues for a wider availability for this modality in the pre-hospital setting.

Bottom Line

Non-invasive positive pressure ventilation is a reasonable out of hospital treatment option for adult patients with undifferentiated severe respiratory distress.

Read More

SGEM#96: Machine Head – NIPPV for Out of Hospital Respiratory Distress.

More References

Vital FMR et al. Non-invasive positive pressure ventilation (CPAP or bilevel NPPV) for cardiogenic pulmonary oedema. Cochrane Database of Systematic Reviews 2013. PMID: 23728654

Ram et al. Non-invasive positive pressure ventilation for treatment of respiratory failure due to exacerbations of chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews 2004. PMID: 14974057