Monitoring physiologic change in the bladder in health and disease. A new biomedical application of near-infrared spectroscopy

Abstract

Biomedical applications of near-infrared spectroscopy (NIRS) utilize non-invasive optical technology to monitor alterations in tissue oxygenation and hemodynamics in real time via changes in concentration of the chromophores oxygenated and deoxygenated hemoglobin. Applications of NIRS to the bladder are novel and recent. Transcutaneous monitoring over the bladder as it fills and empties provides unique physiologic information, as hemodynamic variations in the organ's microcirculation and alterations in oxygen supply, demand and consumption in the detrusor muscle can be inferred. Such information, which is not available by other means, enhances investigation of patients with bladder dysfunction, offers new insights into causal pathology and hence potentially impact choice of pharmaceutical agents. Problem voiding is common, but the principal diagnostic test is invasive, and gives limited diagnostic and therapeutic information (pressure/flow). Continuous wave NIRS instruments are used for bladder monitoring. Initially NIR light was laser-generated; now miniaturized self-contained devices using light emitting diodes, spatial configuration of emitters to detector, and wireless capacity enhance research scope and clinical monitoring potential. NIRS bladder chromophore patterns during filling and voiding differ in health and disease. In addition to adding new knowledge re voiding dysfunction causation, data patterns characteristic of specific pathology have allowed construct of algorithms with comparable discriminant ability to current invasive diagnostic measures. Such data are physiologic because NIRS only detects change during events in the voiding cycle, pathologic changes mirror NIRS-derived effects of physiologic events (hypoxia/ischemia/fatigue) observed in other tissues (muscle/brain/spinal cord), and animal data and independent research corroborate the principal findings.