Brief reportContinuous Positive Airway Pressure vs. Pressure Support Ventilation in Acute Cardiogenic Pulmonary Edema: A Randomized Trial
Introduction
Acute cardiogenic pulmonary edema (ACPE) is a common cause of acute respiratory failure. The main priority in these patients is to achieve adequate oxygenation levels to prevent organ dysfunction and the onset of multiple organ failure (1). The maintenance of peripheral oxygen saturation (SpO2) in the normal range is important to maximize oxygen delivery to the tissues. Despite medical treatment with vasodilators, diuretics, morphine, and supplemental oxygen, a subset of patients, those with severe respiratory distress, are not able to improve gas exchange and require endotracheal intubation (ETI). ETI is associated with significant morbidity, increased hospital length of stay, and upper airway complications due to ETI (2).
In several randomized trials, application of positive intrathoracic pressure, either by non-invasive continuous positive airway pressure (nCPAP) or non-invasive pressure support ventilation (nPSV), has been employed for the treatment of patients who fail to respond to standard medical treatment (SMT) and require respiratory assistance for severe respiratory failure due to ACPE (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16). By increasing intrathoracic pressure, the application of positive pressure to the airways has both respiratory and hemodynamic effects (17, 18). The addition of nCPAP or nPSV to standard treatment has been shown to result in rapid improvements in gas exchange, lung mechanics, work of breathing, and in left ventricle (LV) afterload (3, 4, 5, 6, 9, 11, 13, 14, 17, 19, 20).
Compared to nCPAP, nPSV potentially could unload the respiratory muscles more effectively and reverse or more effectively prevent ventilatory failure, alveolar hypoventilation, and hypercapnia (21).
In one previous study, the authors observed no difference in ETI rate between patients treated with nPSV and those treated with SMT, and another previous study was prematurely terminated because the ETI rate and death rate were higher in patients treated with nPSV compared to those receiving only medical treatment (15, 22). A review of pooled data from studies comparing nPSV with SMT found no benefit of the former in ETI rate, whereas a significant reduction in ETI rate was observed in patients treated with nCPAP when compared with SMT (23, 24, 25, 26).
Three recent meta-analyses have shown that both nCPAP and nPSV reduce the need for ETI in ACPE patients, but studies on nPSV have not yet demonstrated a significant reduction in intubation rate compared to nCPAP, possibly because all of the trials analyzed had insufficient power to demonstrate a difference between the two methods (25, 26, 27, 28).
Non-invasive CPAP alone has been shown to significantly reduce mortality when compared to SMT. A non-significant trend toward reduced mortality was observed in comparing nPSV vs. SMT, probably because of the low power in the studies due to the limited number of patients enrolled (23, 26).
Given the theoretical physiological advantages of nPSV, we conducted a multi-center, prospective, randomized study to investigate whether nPSV, compared to nCPAP, could decrease the ETI rate in patients with ACPE. In addition, we compared the two techniques with respect to mortality rate, improvement in gas exchange, duration of ventilation, and hospital length of stay.
Section snippets
Materials and Methods
The study was approved by the institutional ethics committee. Written consent was obtained from patients' next of kin if patients were unable to give informed consent due to the severity of their disease. The study was conducted in accordance with the Declaration of Helsinki.
The study was performed between January 1, 2003 and May 31, 2005 in three Italian emergency departments (EDs). Teams at all three hospitals were highly skilled in non-invasive ventilation.
Results
Between January 1, 2003 and May 31, 2005, 106 patients were admitted to the ED for an episode of ACPE. There were 26 patients thought to have severe ACPE who were excluded from the study (Figure 1).
We enrolled 80 patients who were randomized to receive either nCPAP (40 patients) or nPSV (40 patients). Patients' characteristics were homogeneous at study enrollment (Table 2). At study enrollment, 30 patients in the nCPAP group and 24 in nPSV group were hypercapnic (arterial carbon dioxide [PaCO2]
Discussion
This study shows that nCPAP and nPSV are similar in resulting in a rapid improvement in vital signs and gas exchange in patients with severe ACPE.
We observed no difference in the proportion of patients who underwent ETI with nCPAP vs. nPSV, similar to previously published data (9, 10, 12, 13, 14).
In agreement with results of previous studies, PaO2/FiO2, pH, RR, HR, and SpO2 improved with both nCPAP and nPSV (9, 12, 13, 14). In addition, the decrease in PaCO2 over time was not significantly
Conclusion
Our study shows that both nCPAP and nPSV are effective treatments for ACPE, improving gas exchange without significant differences in the ETI rate, mortality rate, or hospital length of stay. As highlighted in other studies, the application of intrathoracic positive pressure (either nCPAP or nPSV) is a useful non-pharmacological form of treatment of ACPE (14). We believe that, due to its lower cost and ease of use, nCPAP should be considered as the first-line intervention in patients with
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