A Smart, Self-learning, Automated Programmable Intermittent Epidural Bolus (PIEB) Timer Unit--For Clinical or Research Use
Abstract Number: S-40
Abstract Type: Original Research
Intro: Continuous epidural infusion (CEI) with patient controlled epidural analgesia (PCEA) is widely used for labor analgesia, but the CEI rate may need adjustment over time to improve labor analgesia. Past studies found that programmed intermittent epidural bolus (PIEB) with PCEA results in equivalent labor analgesia with fewer top-up doses and less drug use. However, there is no commercial epidural infusion pump that combines PIEB and PCEA. After creating a PIEB unit that interfaces with commercial pumps, our goal is to build a unit that delivers PIEB with PCEA with a self-learning feature to auto-adjust the CEI or PIEB rate based on PCEA feedback.
Methods: An 8-bit processing unit chip (MC9S08JM60, Freescale Semiconductor) was the brain of the self-learning PIEB unit (Fig 1). A wi-fi chip (WiSNAP-M2, Serial I/O Inc) was used to provide remote access & programming. Output of the unit triggers a relay contact connected to the input of the epidural pump to deliver the PIEB. Using an assembly language program, the processor collects PCEA history as feedback to auto-adjust the PIEB timer interval. PCEA usage history is collected during 8 consecutive sampling periods (2h for a 15 min sampling period). A rule based decision tree determines whether to increase or decrease the PIEB timer interval by a preset “percent correction.” The unit was connected to a GemStar pump (set at 3mL bolus, 5 minutes lockout, max 40 mL/hr without CEI) with the self-learning PIEB timer interval set at 5, 10, & 30 min respectively, each tested over a 24h period with & without the self-learning function enabled. When testing the self-learning function, the sample period was 15 min with a 20% correction, and the PCEA button was activated manually every 30 min for 4h, and then none for 4h.
Results: Comparing against data recorded in the GemStar pump, all the set PIEBs & the self-learning PIEBs were delivered correctly. The accuracy (% time diff of PIEB timer vs pump) was 99.89% (< 1.6 min in 24h). The self-learning function performed as per the set rules to correctly adjust the PIEB interval based on PCEA use. Remote accessing of patient history and settings via wi-fi was successful on an iPad2.
Discussion: This self-learning PIEB timer unit provides a useful clinical tool to provide accurate PIEB plus PCEA with or without CEI while using a single infusion pump. It also provides a research tool to study different feedback algorithms to adjust PIEB rate based on PCEA use.