Assessment of successful epidural steroid injection using photoplethysmogram

ABSTRACT

BACKGROUND:One of effective treatment methods for back pain and radiculopathy is epidural steroid injection (ESI). However, its effectiveness is hard to judge.So, it is strongly urged to develop a method to evaluate the proper injection of ESI. Photoplethysmogram (PPG) is known as a technique to measure blood oxygen saturation. We were intended to study the PPG for the evaluation of the ESI instantaneously. METHODS:All patients were explained for the study protocol to get informed consent.Twenty volunteers were recruited for this study and four of them were allocated in one of 5 ESI levels; L2-3, L3-4, L4-5, L5-S1 and caudal.They were in the lateral position with 4 PPG probes in their both 2nd fingers and 2nd toes.The PPG signals were collected to a device and converted digitally.PPG signal has two components, total absorbance (TA) and oscillating pulse component (OPC).We compared the both toe PPG signals before and after ESI based on the finger PPG. RESULTS:TA changed in 60% of ESI volunteers and L4-L5 and L5-S1 groups had high change rate compared to L2-L3 group.Also, the symptom relief rate of TA and OPC change volunteers of L4-L5 and L5-S1 were 100% but other level had variable relief rate. CONCLUSIONS:It is possible to use the PPG signal to predict ESI success based appropriate signal change.It is also needed to develop other level signal detection method and to modify appropriate guideline for the decision of change of PPG.