There are still few studies on the effects of positive intra-thoracic pressure on ventricular function and spontaneous baroreflex sensitivity changes. Aim of the study is to evaluate, in patients with chronic heart failure with an ejection fraction < 40%, the modifications of ventricular function induced by CPAP (Continuos Positive Airway Pressure) application. All the measurament will be made in basal condition (without CPAP) and with CPAP administration at 10 cmH2O via an oro-nasal mask.~Echocardiograpich evaluation: morphologic and hemodynamic evaluation is obtained with an echocardiographic exmination. Left ventricular measurement will be assessed in M-mode, under two dimensional guide) according to American Society of Echocardiography guidelines. Left ventricular ejection fraction will be assessed with Simpson method.~Right ventricle morphology will be evaluated categorizing dimensions in a) normal, b) mild enlargement, c) severely increased and d) reduced. Right ventricle area will also be quantified in tele-diastole and in meso-sistole in apical 4 chamber and parasternal short-axis.~Baroreflex control of heart rate was assessed by sequence method analysis of continuous blood pressure recordings obtained in basal condition and during CPAP. Data obtained by non invasive assessment of arterial pressure will be analized and values of arterial systolic, diastolic pressure and pulsatory period for each cardiac cicle will be registered.~Assessment via sequence method is founded on identification, every 10 minutes, on sequences characterized by a progressive increase both in pressure both in RR interval or, conversely, by a progressive reduction of pressure and RR interval evaluated on 4 or more cardiac cicles.
To assess modifications of ventricular function induced by CPAP (Continuous Positive Airway Pressure).