An open-source, non-invasive, novel assembly for automated real-time monitoring of continuous bladder irrigation

Abstract

knowledge, none are available on-market, and none have opened their designs for inspection and further development. Open-source medical devices carry several advantages over traditionally developed hardware, which include but are not limited to: improved pace of innovation; modifiability for more specific uses; improved repairability; lower cost; and low potential for vendor lock-in [7]. METHODSThe hematuria monitor (HM) is built with openness and expandability as core principles. The device uses the Arduino open-hardware platform, a popular, easy-to-use development environment that makes it ideal for prototyping devices. HM was also built with secondary goals of being easy to construct, and to keep potential cost-per-unit low. Instructions available on our published openhardware.io page include editable CAD files for 3D-printable enclosures (Figure 1), circuit schematics, code, and data from validation.The processing unit for HM is an Arduino Nano V3.0. The spectral sensing module is a white LED mounted opposite an AS7262 spectrophotometer, passing incident light through a catheter outflow tube latched inside the spectrophotometer shroud (Figure 2), resulting in a reading of transmitted light at the spectrophotometer inversely proportional to the level of hematuria.The current implementation of HM uses a lookup table to estimate outflow colour based on readings from the violet (450nm) wavelength of light, as internal tests demonstrated the greatest sensitivity/reliability of this wavelength on the selected spectrophotometer to differentiate grades of hematuria (not shown). Flow rate is detected through rate-of-change calculations from a load cell from which the catheter outflow bag is mounted. Readout data is displayed via a small screen. We conducted initial laboratory validation of the HM with known serial dilutions of known-hematocrit pig's blood, sealed within portions of catheter outflow bag tubing (Figure 3). 8 dilutions were measured in quintuplicate, ranging from 0-1mL in 10mL saline. The range of these dilutions were corresponding to Lee et al.'s Hematuria Grading Scale (HGS) values of 0-10 [3]. A correlation coefficient analysis was undertaken. We also proceeded to validate the colorimetric function of the device in a ward setting, on twenty patients undergoing CBI. 40 pictures were taken of the spectrophotometer shroud clamped on CBI effluent tubes beside a copy of the HGS, which were rated by three blinded raters on a scale of 0 to 10. These were simplified to an ordinal score from 0 to 5 to match the device readout. The mode of the three human-read grades was taken and compared with device readouts via weighted Kappa. Testing was done under UBC Clinical Ethics Board certificate H20-02012.