Effect of Continuous Positive Airway Pressure on Intrathoracic and Left Ventricular Transmural Pressures in Patients With Congestive Heart Failure

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Abstract
Background Continuous positive airway pressure (CPAP) can improve cardiac function in patients with congestive heart failure (CHF). We hypothesized that this effect might be related to CPAP-induced increases in intrathoracic pressure, which would reduce left ventricular transmural pressure (LVPtm) during systole, thereby decreasing left ventricular afterload. Methods and Results The effect of graduated CPAP from 0 to 10 cm H2O on the above variables was examined over a 75-minute period and compared with a 75-minute time control period without CPAP in two groups of subjects: 15 patients with CHF and 9 healthy subjects. Intrathoracic pressure was estimated from esophageal pressure (Pes), and systolic LVPtm, a determinant of left ventricular afterload, was assessed by subtracting Pes during systole from systolic blood pressure. Cardiac index (CI) was assessed by Doppler echocardiography. At baseline, inspiratory Pes amplitude, which reflects inspiratory muscle force generation, was greater in the patients wi...