Elsevier

Annals of Emergency Medicine

Volume 52, Issue 3, September 2008, Pages 232-241.e1
Annals of Emergency Medicine

Emergency medical services/original research
Out-of-Hospital Continuous Positive Airway Pressure Ventilation Versus Usual Care in Acute Respiratory Failure: A Randomized Controlled Trial

Presented at the International Congress of Emergency Medicine, June 2006, Halifax, Nova Scotia, Canada.
https://doi.org/10.1016/j.annemergmed.2008.01.006Get rights and content

Study objective

Continuous positive airway pressure ventilation (CPAP) in appropriately selected patients with acute respiratory failure has been shown to reduce the need for tracheal intubation in hospital. Despite several case series, the effectiveness of out-of-hospital CPAP has not been rigorously studied. We performed a prospective, randomized, nonblinded, controlled trial to determine whether patients in severe respiratory distress treated with CPAP in the out-of-hospital setting have lower overall tracheal intubation rates than those treated with usual care.

Methods

Out-of-hospital patients in severe respiratory distress, with failing respiratory efforts, were eligible for the study. The study was approved under exception to informed consent guidelines. Patients were randomized to receive either usual care, including conventional medications plus oxygen by facemask, bag-valve-mask ventilation, or tracheal intubation, or conventional medications plus out-of-hospital CPAP. The primary outcome was need for tracheal intubation during the out-of-hospital/hospital episode of care. Mortality and length of stay were secondary outcomes of interest.

Results

In total, 71 patients were enrolled into the study, with 1 patient in each group lost to follow-up after refusing full consent. There were no important differences in baseline physiologic parameters, out-of-hospital scene times, or emergency department diagnosis between groups. In the usual care group, 17 of 34 (50%) patients were intubated versus 7 of 35 (20%) in the CPAP group (unadjusted odds ratio [OR] 0.25; 95% confidence interval [CI] 0.09 to 0.73; adjusted OR 0.16; 95% CI 0.04 to 0.7; number needed to treat 3; 95% CI 2 to 12). Mortality was 12 of 34 (35.3%) in the usual care versus 5 of 35 (14.3%) in the CPAP group (unadjusted OR 0.3; 95% CI 0.09 to 0.99).

Conclusion

Paramedics can be trained to use CPAP for patients in severe respiratory failure. There was an absolute reduction in tracheal intubation rate of 30% and an absolute reduction in mortality of 21% in appropriately selected out-of-hospital patients who received CPAP instead of usual care. Larger, multicenter studies are recommended to confirm this observed benefit seen in this relatively small trial.

Introduction

Respiratory distress is a common and important presentation to emergency medical services (EMS), for which outcome studies must be done to validate out-of-hospital interventions.1, 2 Individuals at the severe end of this spectrum whose respiratory efforts are failing are in need of some degree of immediate ventilatory support. Such patients usually receive positive-pressure ventilation by bag-valve-mask ventilation or tracheal intubation in the out-of-hospital setting before their arrival at an emergency department (ED). Out-of-hospital intubation attempts in non–cardiac arrest patients are less successful and have higher rates of aspiration of gastric contents than those performed in the ED.3, 4 In addition, patients arriving at an ED already intubated may be more likely to remain so, thus exposing them to the risk of nosocomially acquired pneumonia while being mechanically ventilated in an ICU, potentially doubling their mortality risk.5, 6

Noninvasive ventilation using the modes of CPAP, pressure support ventilation, bilevel positive airway pressure, or noninvasive positive pressure ventilation is recommended in patients with respiratory disorders who remain in acute respiratory failure despite conventional therapy before invasive mechanical ventilation is considered.7, 8 In appropriately selected ED patients, this results in an early improvement in cardiorespiratory status, decreases the need for subsequent tracheal intubation, and reduces mortality.9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 Noninvasive ventilation using CPAP has shown the most benefit in acute cardiogenic pulmonary edema patients, but those with other causes of acute respiratory failure, including exacerbations of chronic obstructive pulmonary disease and asthma, benefit also. A recent meta-analysis of trials comparing patients with acute respiratory failure treated with noninvasive ventilation to those receiving tracheal intubation demonstrated significantly lower rates of pneumonia in the noninvasive ventilation group.24

Although it may be desirable to avoid tracheal intubation and its potential complications for acute respiratory failure patients by using CPAP in the out-of-hospital setting, it is not known whether the hospital-demonstrated benefits of CPAP are mitigated by the unique problems presented by the out-of-hospital environment (eg, diagnostic uncertainty, transport time pressures, gear damage from frequent transport, lack of bedside physician oversight). The evidence for CPAP in the out-of-hospital setting is limited only to several case series and 1 nonrandomized study.25, 26, 27, 28, 29, 30, 31 There is an ethical, scientific, and fiscal imperative to require that therapies shown to be efficacious in hospitals be evaluated in the out-of-hospital setting to ensure their effectiveness before their introduction.32, 33 The purpose of this study was to determine whether out-of-hospital CPAP reduced the subsequent need for out-of-hospital or inhospital tracheal intubation in patients in severe respiratory distress who paramedics assessed as requiring some degree of out-of-hospital positive-pressure ventilatory support.

Section snippets

Study Design

This prospective, randomized, controlled, nonblinded trial was registered with ClinicalTrials.gov (identifier NCT00405314).

Setting

The trial was conducted between July 2002 and March 2006. EMS in the study region are provided under a public utility model in which the government owns all ambulances and equipment and provides fully integrated medical oversight, including continuous online physician coverage. The regulator (government agency) oversees a single contractor who provides out-of-hospital

Results

A total of 71 patients were randomized, 35 into usual care and 36 into CPAP (Figure 1). Two patients (1 in each group) refused the ongoing use of their data once their condition stabilized. The remaining 69 patients were followed until death in hospital or discharge. Two patients were enrolled in the study twice: one was randomized to usual care both times and the second was randomized to CPAP both times. Neither was subsequently intubated. One patient was enrolled 6 times, 4 times to CPAP and

Limitations

There are a few limitations to this study worthy of discussion. The number of patients screened who met eligibility criteria and then were not enrolled or refused the initial consent process was not formally recorded (by informal measurement, the number was small). Thus, we cannot exclude the possibility that initial refusers were somehow systematically different from study participants.

No validated severity of respiratory distress score40, 41, 42, 43 was used to determine eligibility, which,

Discussion

This prospective randomized comparison of out-of-hospital CPAP versus usual care for patients with severe respiratory distress shows a significant benefit for patients treated with CPAP with respect to need for subsequent intubation. To our knowledge, this is the first randomized controlled out-of-hospital study of the effectiveness of CPAP and the only one to include patients in severe respiratory distress from all causes.

Several reports document the out-of-hospital use of CPAP in patients

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    Supervising editor: Theodore R. Delbridge, MD, MPH

    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, that might create any potential conflict of interest. The authors have stated that no such relationships exist. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement. This study protocol was approved by Capital District Health Authority Research Ethics Board. Their file number is CDHA 2000-305, Clinical Trials.gov Identifier NCT00405314.

    Author contributions: JT, DAP, SA-S, and DJB conceived and designed the trial. JT, DAP, SA-S, and DJB obtained the funding. JT, DAP, SA-S, and DJB supervised the conduct of the trial and data collection. SA-S supervised management of the data, including quality control. JT, DAP, and DJB supervised the recruitment by paramedics. SA-S provided statistical advice on study design and statistical methodology and conducted descriptive data analyses. JT drafted the first copy of the article, and all authors contributed substantially to its revisions. JT and DAP take responsibility for the paper as a whole.

    Publication date: Available online April 3, 2008.

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