Acute Heart Failure 　　Elevations in intrathoracic pressure, whether from CPAP or BIPAP, can have profound effects on cardiac function through both preload and afterload reduction, according to Nicholas Hill, MD,[6] of Tufts University, Boston, Massachusetts. On the one hand, in hypovolemic patients, this preload reduction can seriously impair cardiac output and blood pressure. On the other hand, however, in the patient with acute heart failure, this preload and afterload reduction can have particularly beneficial effects on cardiac output and blood pressure. Moreover, alveolar recruitment in these patients from CPAP/BIPAP can improve oxygenation and lung mechanics such that the inspiratory work of breathing is reduced. 　　CPAP, through NIV devices, has been shown in multiple trials of acute heart failure patients to improve oxygenation, cardiac function, and the need for endotracheal intubation.[1] In these studies, however, length of stay and mortality have not been affected. In contrast, trials using BIPAP in these patients have yielded confusing results, although they are theoretically attractive because inspiratory work of breathing should be further reduced. Specifically, while studies have confirmed lower inspiratory work, less dyspnea, and fewer endotracheal intubations using BIPAP vs CPAP in these patients, one randomized trial showed an increased incidence of myocardial infarction in the BIPAP group.[7] In trying to understand this unexpected observation, concern has been raised about the effectiveness of the BIPAP device and the uncontrolled medical management of the cardiac failure patients. New trials are ongoing to better address these issues. 版权所有：好医生网站