Respiratory function after cardiac surgery

Abstract

Cardiac surgery is complicated by decreased postoperative respiratory muscle strength and spirometry with accompanying increased atelectasis. The specific respiratory symptoms attributable to these physiologic changes are unknown, and this study looked at the symptoms and underlying physiology. Convenience sampling of observational cohort. Tertiary care university hospital. One hundred thirty-eight patients undergoing elective surgery were enrolled. Changes from admission to 8-week postoperative values in atelectasis, pleural effusions, spirometry (forced vital capacity and forced expiratory volume in one second), and respiratory muscle strength (negative inspiratory pressure) were measured. These physiologic changes were compared with changes in respiratory symptoms of cough, wheeze, phlegm, and dyspnea on walking up a slight hill noted from admission to 8-week follow-up by stepward logistic regression. Spirometry and negative inspiratory pressure decreased and atelectasis increased from admission to discharge. These disturbances had only incompletely resolved at 8-week follow-up. Some patients reported fewer symptoms of cough (11%), phlegm (9%), wheeze (35%), and dyspnea (46%) at 8 weeks follow-up. Other patients reported increased symptoms of cough (15%), phlegm (10%), wheeze (6%), and dyspnea (4%) at 8 weeks follow-up. Residual atelectasis at 8 weeks was predictive of fewer symptoms of dyspnea (odds ratio [OR] 0.335, p = 0.199; 95% confidence interval [CI] 0.188, 0.597), increased symptoms of dyspnea (OR 855, p = 0.006; 95% CI 6.6, 11052), and increased symptoms of cough (OR 260, p = 0.023; 95% CI 2.13, 31829). Negative inspiratory pressure at 8 weeks was predictive of fewer symptoms of dyspnea (OR 1.05, p = 0.032; 95% CI 1.02, 1.09) and increased symptoms of wheeze (OR 0.7, p = 0.45; 95% CI 0.533, 0999). Forced vital capacity at 8 weeks was predictive of increased symptoms of wheeze (OR 0.005; p = 0.015; 95% CI 0.0060, 0.775). Postoperative changes in respiratory muscle strength and spirometry can persist up to at least 8 weeks postoperatively. Many patients report a change in respiratory symptoms of cough, phlegm, dyspnea, or wheeze. The change in respiratory symptoms at 8 weeks is correlated with residual respiratory muscle weakness, decrease in spirometry, and residual atelectasis.