Epidural Wave Form Analysis vs Fluoroscopic Guidance for Thoracic Epidural Placement

The primary objective of this study is to compare the effectiveness of epidural waveform analysis (EWA) with fluoroscopic guidance for confirmation of successful epidural placement. In this study, participants will undergo both EWA and fluoroscopy. EWA involves measuring the pressure in the epidural space once accessed and determining whether or not a waveform that corresponds with the participant's heart rate is present. The pressure measuring apparatus is the same that is used for direct pressure monitoring elsewhere in the body (i.e. invasive arterial catheters or intracranial pressure monitoring).