Prevalence and Implications of Abnormal Respiratory Patterns in Cardiac Surgery: A Prospective Cohort Study

Objective To investigate the prevalence and impact of abnormal respiratory patterns in cardiac surgery patients. Design Prospective cohort study. Setting Tertiary hospital. Participants Patients scheduled for elective coronary artery bypass graft surgery. Interventions None. Measurements and Main Results Pulmonary function tests were performed in 454 patients before surgery. Abnormal respiratory patterns were defined as follows: obstructive (forced expiratory volume in 1 s [FEV₁]/forced vital capacity [FVC]<0.70), restrictive (FEV₁/FVC≥0.70 and FVC<80% of predicted), and mixed (FEV₁/FVC<0.70 and both FEV₁ and FVC<80% of predicted). Of the 31 patients with a history of chronic obstructive pulmonary disease, no abnormal respiratory pattern was confirmed in 5. Of the 423 patients without a history of lung disease, the authors newly identified 57 obstructive, 46 restrictive, and 4 mixed patterns. Therefore, lung disease was reclassified in 24.7% of cases. Independent predictors of obstructive pattern were age, male sex, history of smoking, and chronic obstructive pulmonary disease. Obstructive lung disease was associated with 16 hours or longer ventilation. A reduced FEV₁ was associated with a likelihood of atrial fibrillation (1-L decrement, odds ratio: 1.38, 95% confidence interval: 1.01-to-1.90, p = 0.04) and hospitalization time (regression coefficient: 1.23, 95% confidence interval: 0.54-to-1.91, p<0.001). Conclusions Abnormal respiratory patterns are common and often underdiagnosed in the cardiac surgery setting. Pulmonary function tests help reveal patients at risk of complications and may provide an opportunity for intervention.