Andrew Macnab, MD, Lynn Stothers, MD.
University of British Columbia, Vancouver, BC, Canada
Presented on May 22, 2007
Introduction and Objective: Near Infrared Spectroscopy (NIRS) is a transcutaneous monitoring tool using light in the near infrared region to monitor changes in concentrations of mixed arterial/venous oxygenated (HbO2) and de-oxygenated (Hb) hemoglobin distribution within the detrusor. The objective was to measure and report the discriminant ability of NIRS parameters in relation to obstruction as defined by pressure flow nomograms in men.
Methods: 25 males (aged 55 to 76) presenting with complaints of obstructive LUTS, International Prostate symptoms scores (IPSS) greater than 12 participated. Patients underwent multichannel urodynamics and simultaneous NIRS data collection at 6Hz intervals. NIRO-300 (Hamamatsu Japan) optodes were positioned suprapubically. Urodynamics included non invasive uroflow followed by two filling cystometrograms and two pressure flow studies per subject using a filling rate of 50 ml/min with sterile water and 6french catheters.
Results: Based on their pressure flow nomograms 15 men had obstruction, 3 were in the equivocal zone and 7 were in the normal range. Prostate symptoms scores ranged from 13-20 with a mean of 18. NIRS shows good discriminant ability tested by the area under the Receiver Operating Characteristic (ROC) curve. The values for four ROC curves were examined. The most discriminant was the ROC curve for time from first change in Hb and HbO2 baseline to start of uroflow which was 0.91. For time from first bladder activity to start of uroflow 1-specificity was 0.20 and sensitivity was 0.78. The other three discriminant variables examined were the absolute change in Hb over the pressure flow session with an ROC value of 0.81, absolute changes in HbO2 concentration over the pressure flow session with an ROC value of 0.84 and absolute change in the concentration of Cyt over the pressure flow session with an ROC value of 0.77.
Conclusions: NIRS has good discriminant ability to assess obstruction based on ROC curves, the most discriminant being the time from first change in Hb and HbO2 from baseline with a full bladder to the start of uroflow. The time from bladder activity based on NIRS changes from baseline provides the most reliable indicator of obstruction in a non invasive measure.
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