Despiratory dysfunction is an important cause of postoperative morbidity after open heart surgery. Atelectasis and hypoxemia are the main clinical manifestations. Factors promoting atelectasis are thought to be reduced lung volume’ and small airway closure. Hypoxemia may reflect increased intrapul-monary shunt and increased ventilation-perfusion mismatch. These effects could be due to the surgical procedure itself and/or the residual effect of anesthesia.
To improve oxygenation and reopen atelectatic lung units in these patients, the use of a low level (5 to 10 cm H20) of PEEP has been advocated both as a prophylactic and as a therapeutic modality. Although some studies have shown that PEEP results in moderate improvement of arterial oxygenation, they failed to show roentgenologic improvement in atelectasis or reduction in postoperative pulmonary complications.* To our knowledge, detailed analysis of the effects of PEEP on respiratory mechanics in these patients has not been performed previously.
In the present investigation, we studied the effects of different levels of PEEP on static compliance of the respiratory system and on recruitment of lung units in ten open heart surgery patients in the immediate postoperative period.