Effect of PEEP on Cardiac Function

Inclusion Criteria: * 1\. Age ≥ 18 years * 2\. Scheduled to undergo cardiac surgery requiring general anesthesia * 3\. Planned use of intraoperative transesophageal echocardiography (TEE) as part of routine clinical care * 4\. Planned placement of a pulmonary artery catheter as part of clinical care (Pulmonary artery catheter placement will be performed solely based on clinical judgment by the treating anesthesia and surgical teams. At our institution, pulmonary artery catheters are routinely placed in cardiac surgery patients with clinical indications including: * preoperative pulmonary hypertension (e.g., estimated PCWP \>20 mmHg or elevated filling pressures on preoperative echocardiography), * right ventricular dysfunction or suspected RV failure (preoperative visual TTE assessment), * significant cardiopulmonary comorbidity, * or anticipated complex, prolonged, or high-acuity cardiac surgery. The research team will not influence decisions regarding catheter placement. Only patients already scheduled to receive a clinically indicated pulmonary artery catheter will be eligible for enrollment.) * 5\. Able and willing to provide written informed consent prior to surgery Exclusion Criteria: * 1\. Significant arrhythmia (e.g., atrial fibrillation with uncontrolled ventricular response or other rhythm disturbances) that would interfere with reliable pressure waveform or echocardiographic measurements. * 2\. Severe valvular disease where protocol-related PEEP changes…