Open source device monitors hematuria during continuous bladder irrigation

Researchers from the University of British Columbia, Vancouver have developed an open source, non-invasive, and inexpensive device for automatic hematuria monitoring in continuous bladder irrigation (CBI).¹

The hematuria monitor (HM) was discussed in a late-breaking abstract at the 2022 American Urological Association Annual Meeting in New Orleans, Louisiana.

In discussing the background for the study, co-author Alireza Habibi, a medical student at the University of British Columbia, explained that although CBI is a common intervention following endourologic surgery, it is reliant upon subjective assessment and adjustments and is labor intensive. In addition, assessment of grade of hematuria is user dependent.

The investigators reported that the HM utilizes the Arduino open-hardware platform. Full hardware specifications for all components can be found online, and the instructions are available at www.github.com/malyalar/CBI-monitor. They include CAD files, files for enclosures, circuit schematics and layouts, source code, and data from validity analysis.

“The spectral sensing device is a 3D printed shroud where a white LED is mounted opposite to a AS7262 spectrophotometer module (AMS). Incident light is passed through a CBI catheter outflow tube clipped inside the shroud, resulting in a reading at the photodiode proportional to the hematuria in the tube,” wrote the authors.

The HM measures flow rate via rate-of-change calculation at a load cell. The catheter outflow bag is mounted at the load cell. A small TFT screen delivers telemetry. The investigators conducted testing using 5 serial dilutions of pigs’ blood in normal saline that encompassed a full range of hematuria grades and sealed within portions of catheter outflow bag tubing.

The investigators reported that the HM continuously monitors flow rate, estimates blood concentrations, and outputs alarms in the event of obstruction in laboratory settings. It can also display an alarm based on estimates of hematuria grade and flow rate adequacy. A limitation of the system is that in its current form, it does not adjust the flow rate of CBI automatically. The system costs $35 CAD in its most basic form, and no special skills or tools are required to build it.

“In testing, the HM achieved a correlation coefficient of 0.97, P = .006 for its estimations of hematuria against 5 known serial dilutions (in triplicate) of pig’s blood ranging from 0.05 mL to 0.3 mL in 10 mL saline,” wrote the authors.

In his closing remarks, Habibi said his group plans to conduct a study looking at agreement between measurements, with the goal of improved patient outcomes and CBI management standardization.

Reference

1. Malyala R, Habibi A, Phillips D, et al. An open source, non-invasive, and inexpensive assembly for automatic hematuria monitoring in continuous bladder irrigation. 2022;207(5S):e1043. doi:10.1097/JU.0000000000002670.06