Pulmonary dysfunction after coronary artery bypass surgery

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Respiratory dysfunction and arterial hypoxemia are common causes of morbidity following cardiac surgery utilizing extracorporeal circulation. Predisposing factors can be classified as (1) related to the surgical procedure such as opening the chest, opening the pleura, trauma, postoperative pleural effusion, hemothorax, or pneumothorax; (2) associated preoperative pathologic changes such as restrictive or obstructive lung disease, chronic lung congestion secondary to heart disease; and (3) related to cardiopulmonary bypass technique with its associated physiologic and histologic changes in the lung structure.

We studied the degree of respiratory dysfunction and the course of recovery in 357 consecutive patients who had undergone coronary artery bypass surgery and were considered clinically capable of supporting their own pulmonary functions without prolonged mechanical assistance after surgery. Postoperative pulmonary management was standardized; all patients were mechanically ventilated overnight. F1O2 and ventilatory parameters were adjusted to maintain PaO2 80 to 120 mm Hg and PaCO2 35 to 40 mm Hg. Patients who had vital capacity 10 to 15 cc/kg body weight, PaO2 >80 mm Hg inspiratory negative Pr >30 cm H2O were weaned from mechanical ventilation. All patients received routine chest physiotherapy until the fifth postoperative day. Computer analysis was used to compare postoperative screening spirometry results done on the seventh postoperative day with preoperative values, which were used as controls. There was a significant reduction in vital capacity, forced vital capacity, forced expiratory flow rate, and peak expiratory flow rate (Table 1). The FEV1/FVC ratio remained the same, indicating that the changes are mainly restrictive and . . .



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