It has been shown that compared to conventional treatment, both continuous positive airway pressure (CPAP) and positive pressure noninvasive ventilation (NPPV) improve vital signs and physiologic variables, and reduce intubation rate, in patients with acute cardiogenic pulmonary edema (ACPE).
Despite a physiologic rationale that NPPV should offer greater benefit than CPAP, NPPV has not been found to offer any advantages regarding intubation rate or mortality compared with CPAP also in ACPE patients with acute respiratory acidosis.
As a general rule, when neuromuscular central drive activity is preserved, acute respiratory acidosis is due to a pump failure, that is an unbalance between respiratory muscle capacity and respiratory workload: as a consequence an inspiratory support, by means of invasive or noninvasive mechanical ventilaton, to unload the inspiratory fatiguing muscles is necessary to improve tidal volume.
However, in the case of ACPE the simple application of CPAP could be enough to improve respiratory mechanics and early decrease the unbalance between inspiratory muscles and respiratory workload. As a matter of fact, it was shown with experimental procedures that diaphragm muscle can significantly recover from fatigue within about 60 minutes after rest.