The purpose of this single arm, open label study will be to compare and evaluate the sensitivity and specificity of CompuFlo to detect epidural pulse waveforms (EPW) to assess the correct placement of the catheter in the epidural space when compared to the standard pressure transducer.

40 patients who had an epidural functioning catheter previously positioned for anesthesia or analgesia will be enrolled. After removing the epidural filter and after having zeroed the instrument, the investigator will connect in a random fashion sequence, a standard pressure transducer attached to a standard invasive blood pressure monitor or to the CompuFlo CathCheck instrument to observe and record the occurrence of epidural pulsatile waveform.

The investigator will also note and evaluate:

The volume of saline priming necessary to obtain the waveform The effects of patient's position on the occurrence and amplitude of epidural pulsatile waveform

Inclusion Criteria:

• patients with an epidural lumbar catheter for anesthesia or analgesia

Exclusion Criteria:

• patients with malfunction or dislodgement of the epidural catheter