A wearable optical sensor monitoring bladder urine volume to aid rehabilitation following spinal cord injury

Abstract

Background: Spinal cord injury (SCI) compromises bladder function, including the ability to sense the need to void. Overdistension leads to involuntary leakage and endangers health through upper renal tract pressure damage and autonomic dysreflexia. A monitor warning the bladder is full will allow optimal use of manual expression or intermittent catheterization. Methods: The wearable interface is a silicone sheet worn over the bladder, which incorporates a grid of 4 near-infrared LED transmitters with 3 wavelengths (2 at 950 nm for water detection and 2 of 760 and 850 nm for conventional monitoring of O2Hb and HHb). The system has 8 continuous-wave measurement channels and monitors at 2 different vertical levels to detect variation in bladder fullness; IOD’s of 30 and 40mm provide information at 2 depths. Associations between optical densities during bladder emptying and then during natural filling were compared. Results: Data from 4 male and one female subject were analyzed. The optical densities recorded at the lower vertical locations showed positive correlation with the voiding rate (ratio of scale signal), and O2Hb and HHb concentration changes at higher vertical locations revealed muscle activation prior to voiding. Discussion: This pilot study provides proof of the feasibility of using a 950nm wavelength incorporated into a wearable NIRS bladder monitoring system to transcutaneously and non-invasively detect changes in bladder volume in real-time. Conclusions: Ongoing research is warranted to further evaluate the system as the bladder fills naturally; and establish the clinical value of the data obtained to patients living with spinal cord injury

Near infrared spectroscopy of the central nervous system: monitoring oxygenation in the neonatal brain and in the spinal cord following traumatic injury

“…62 It is undeniable that a lack of such collaboration in the past compromised the translation of NIRS-related ideas and experimental technologies from bench to bedside that had the potential to benefit both clinicians in this field and their patients. 63 Reluctance to explore the ability of fNIRS to identify neural elements related to bladder sensation and control of voiding also needs to be overcome, so that the unique information related to brain-mediated aspects of urologic disease that can be derived through fNIRS can be gathered from effective research and then used to expand knowledge and improve care. 64,65 Future directions need to focus on the safety and reliability aspects of the sensors now being used, and where they can and cannot contribute robust data able to positively influence care; in this context clinical translation of the spinal cord NIRS system is ongoing and lessons relevant to future safe use need to be learned.…”