Original Contribution
Continuous positive airway pressure for cardiogenic pulmonary edema: a randomized study,☆☆

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Abstract

Study Objective

The purpose of this randomized controlled trial was to determine the immediate and delayed effects of noninvasive ventilation for patients in acute cardiogenic pulmonary edema (ACPE) in addition to aggressive usual care in a medical prehospital setting.

Methods

Out-of-hospital patients in severe ACPE were eligible for the study. Patients were randomized to receive either usual care, including conventional optimal treatment with furosemide, oxygen, and high-dose boluses of isosorbide dinitrate plus oxygen, or conventional medications plus out-of-hospital continuous positive airway pressure (CPAP). The primary outcome was the treatment success defined as all of respiratory rate less than 25 breaths per minute and oxygen saturation of greater than 90% at the end of 1-hour study. Secondary end points included death during 30 days after inclusion. Lengths of intensive care unit and hospital stays were also recorded.

Results

In total, 124 patients were enrolled into the study. The 2 groups had similar baseline characteristics. For the primary outcome analysis, 22 (35.5%) of 62 patients were considered as experiencing a treatment success in the usual care group vs 19 (31.7%) of 60 in the CPAP group (P = .65). Seven patients died within 30 days in the usual care group vs 6 in the CPAP group (P = .52). There were no statistically significant differences between the treatment groups for length of stay either in hospital or in the intensive care unit.

Conclusion

In the prehospital setting, in spite of its potential advantages for patients in ACPE, CPAP may not be preferred to a strict optimal intravenous treatment.

Introduction

Acute cardiogenic pulmonary edema (ACPE) is a frequent presenting disease for acute out-of-hospital practice. Acute left ventricular failure may occur from a variety of processes that rapidly deteriorates to this generalized cardiopulmonary disorder. The classical treatment of out-of-hospital ACPE includes supplemental oxygen, vasodilators, and loop diuretics. If not effective or because of the associated respiratory depression, tracheal intubation and mechanical ventilation are often needed, which, by themselves are associated with a worse prognosis [1]. Bilevel positive airway pressure (BiPAP) and continuous positive airway pressure (CPAP) has been proposed to avoid mechanical ventilation in severe ACPE [2], [3], [4], [5], [6]. The overall effect of CPAP in the acute management of ACPE is to improve cardiorespiratory function and sustained tissue oxygenation. This technique not only decreases intrapulmonary shunt [6] and work of breathing [7] but also reduces left ventricular afterload and both right and left ventricular preload [8]. Collectively, the available data suggest that CPAP is effective in reduction in intubation rate and that there is a trend toward reduced mortality in emergency departments [9]. Some randomized prospective trials [10], [11], [12] have demonstrated significant improvements in vital signs and gas exchange as well as drastic reductions in intubation rates attributable to the use of CPAP. In patients with ACPE, with no effect on short-term mortality. However, the evidence for CPAP in the out-of-hospital setting is limited only to several case series, nonrandomized studies, and few randomized studies [13], [14], [15], [16], [17], [18], [19], [20], [21]. One randomized study focused on severe respiratory distress with paramedic-staffed ambulances [20], and another study focused on immediate effects on early vs late CPAP in a prehospital setting with physician-staffed ambulances [21]. To our knowledge, no study focused on ACPE in a prehospital setting compared CPAP to a placebo treatment, and no study was focused on delayed effects of CPAP vs usual care for ACPE (eg, later than in-hospital death). The purpose of this study was then to determine whether out-of-hospital treatment with CPAP improves significantly respiratory distress for patients in ACPE.

Section snippets

Study design

This prospective, randomized, controlled, nonblinded trial was registered with ClinicalTrials.gov (identifier NCT00439075). Enrollment began in September 2006 and finished when the desired number of patients was reached in March 2008. The regional ethics committee (Toulouse II, France) approved this study, with exception to preliminary written informed consent. Patients meeting eligibility criteria were read a standard statement that briefly explained the nature of the study, and if they (or

Results

One hundred ninety consecutive ACPE were screened between September 2006 and March 2008. One hundred twenty-four patients were enrolled in the study (Fig. 1). Sixty-two patients were randomly assigned to usual care and 62 to CPAP. No patient was enrolled in the study twice. The 2 groups had similar baseline characteristics (see Table 1), with a nonsignificant trend toward a difference in the rate of previous ACPE between the 2 groups (45% in the usual care group vs 30% in the CPAP group; P =

Discussion

Our study was designed to ascertain that the known mechanisms by which CPAP works in ACPE would result in an improved outcome in addition to usual care in a medical prehospital setting. In the present study, when adding CPAP in one group, patients did not exhibit significantly less symptoms of respiratory fatigue. Moreover, intubation rate, overall mortality, and hospital length of stay were equally distributed in the 2 treatment groups. There are still controversial studies in the literature;

Conclusion

In the prehospital setting, in spite of its potential advantages for patients in ACPE, CPAP may not be preferred to a strict optimal treatment including low-dose morphine, furosemide, oxygen, and high-dose boluses of isosorbide dinitrate unrestricted according to clinical response.

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      Six of the 7 included trials used CPAP in the treatment arm of the study14-18,20 and 1 used BiPAP.19 Four different commercial NIPPV systems were used to generate positive pressure, including an external pressure regulator (WhisperFlow,14,18 Downflow16), turbulent flow valve (Boussignac15), and portable ventilator (Oxylog 300017,19,20). Although analysis is beyond the scope of this review, each system has its strengths and weaknesses with respect to ease of paramedic use, cost, maximum therapy length because of oxygen requirements, and compatibility with existing hospital hardware.27

    • Assessment of the addition of prehospital continuous positive airway pressure (CPAP) to an urban emergency medical services (EMS) system in persons with severe respiratory distress

      2013, Journal of Emergency Medicine
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      Similar to findings on hospital LOS, recent investigations on the effect of prehospital CPAP on mortality also have been inconsistent (38,43,47,48). Our findings are consistent with recent studies that did not demonstrate significant differences in 7- and 30-day mortality when comparing patients receiving standard oxygen therapy and those undergoing non-invasive ventilation (47,48). Interestingly, Gray et al. did not find a difference in mortality between those receiving standard oxygen therapy and those undergoing non-invasive ventilation (9.8% vs. 9.5%, respectively; p = 0.87) despite patients undergoing non-invasive ventilation for a minimum of 2 h (48).

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    Work attributed to: SAMU 31. CHU Purpan. Toulouse, France.

    ☆☆

    Support: The authors have no commercial associations or sources of support that might pose a conflict of interest. Support was provided solely by institutional sources; this work was sponsored by the University Hospital of Toulouse for regulatory and ethic submission.

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