The concept of conducting transesophageal echocardiography (TEE) during CPR was first tested in a randomized trial. The study involved patients in prolonged out-of-hospital cardiac arrest (OHCA) who were very ill. The method for more anatomically targeted CPR did not produce the expected results. TEE is performed by inserting a probe into the esophagus after local anesthesia of the oral cavity and pharynx. The examination takes place in a lying position under the supervision of a doctor and a nurse, with the patient connected to an EKG. Esophageal echocardiography allows for more accurate imaging of the heart due to its proximity to the back wall of the heart compared to a transthoracic approach through the chest.