Haemodynamics of cardiac tamponade during various modes of ventilation.

Cardiac output and pleural, pericardial, arterial and cardiac pressures were measured in baboons during different modes of ventilation in the presence of acute cardiac tamponade. Fluctuations in pleural pressure during intermittent positive pressure ventilation were transmitted to the pericardial fluid. Cardiac output and transmural right ventricular end-diastolic pressure were significantly greater during spontaneous ventilation than during intermittent positive pressure ventilation with or without positive end-expiratory pressure. It is recommended that a patient undergoing surgery for cardiac tamponade be allowed to breathe spontaneously until the chest is opened and the pericardium incised.