Comparison of Oxygen Reserve Index and Spirometry in Predicting Respiratory Complications After Coronary Artery Bypass Surgery

"All participants in this single-arm diagnostic study will undergo preoperative evaluation involving two non-invasive respiratory assessment methods: the Oxygen Reserve Index (ORI) and spirometry. ORI will be measured using a multi-wavelength pulse co-oximetry sensor placed on the patient's fingertip. This sensor provides a continuous, real-time index (ranging from 0.00 to 1.00) that reflects the patient's oxygen reserve within a PaO₂ range of approximately 100-200 mmHg.~Spirometry will be performed using standard pulmonary function testing protocols. Each patient will be instructed to perform forced expiratory maneuvers to obtain parameters including forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), and the FEV₁/FVC ratio. These values will be recorded prior to surgery and interpreted according to internationally accepted reference ranges."