Hemodynamic effects of nasal CPAP examined by Doppler echocardiography. The effects of incremental application of nasal continuous positive airway pressure (0 to 15 cm H2O) on heart rate, pulmonary artery pressure, and cardiac index were studied noninvasively by Doppler echocardiography. By two-way analysis of variance within two groups (19 normal volunteers and six sleep apnea patients), no significant effects on heart rate, pulmonary artery pressure, ventricular size, or cardiac index could be found with increasing positive intrathoracic pressures and consequent lung hyperinflation. In subjects with normal cardiac function, nasal CPAP is safe from a hemodynamic viewpoint. This simple, repeatable and noninvasive technique may be used to assess the clinical safety and efficacy of prescribed nasal CPAP on cardiac hemodynamics in individual patients. 