Association of preoperative spirometry with postoperative pulmonary complications and prolonged length of hospital stay following coronary artery graft surgery

<bold>Purpose:</bold> Ventilatory function measured by spirometry is commonly performed preoperatively in people undergoing coronary artery graft surgery (CAGS). Minimal information exists on the associations between spirometry parameters, postoperative pulmonary complications (PPC), and prolonged (≥ 7 days) length of hospital stay (LOHS) following cardiac surgery. This study aims to investigate the relationships between preoperative spirometry values with both PPC and prolonged LOHS in patients undergoing CAGS. <bold>Methods:</bold> This retrospective observational cohort study analysed patients undergoing preoperative spirometry and CAGS at Royal Prince Alfred Hospital between January 2017 and December 2021. Forced expiratory volume in the first one second (FEV1) and forced vital capacity (FVC) were measured. For each patient, both were converted to percentage of predicted value for a healthy person with matched characteristics termed FEV1%pred and FVC%pred respectively. The association between FEV1%pred and FVC%pred against the incidence of PPC and prolonged LOHS was determined using multivariate logistic regression analysis. <bold>Results:</bold> 956 patients [773 male, mean (SD): age 65 (10) years; BMI 29 (6)] were analysed. Lower FEV1%pred was associated with PPC (odds ratio: 0.99; 95% CI: 0.98 to 0.99, P=0.009) and prolonged LOHS (odds ratio: 0.99; 95% CI: 0.98 to 0.99, P=0.003). FVC%pred was not associated with PPC or prolonged LOHS in multivariate analyses. <bold>Conclusions:</bold> Spirometry, to identify FEV1%pred, could be valuable in predicting risk of PPC and prolonged LOHS in people undergoing CAGS and therefore could be useful in identifying at risk patients.