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ASME J of Medical Diagnostics. 2018;1(4):041001-041001-8. doi:10.1115/1.4040498.
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Treatment of vision-threating elevated intraocular pressure (IOP) for severe glaucoma may require implantation of a glaucoma drainage device (GDD) to shunt aqueous humor (AH) from the anterior chamber of the eye and lower IOP to acceptable levels between 8 and 21 mm Hg. Nonvalved GDDs (NVGDDs) cannot maintain IOP in that acceptable range during the early postoperative period and require intra-operative modifications for IOP control during the first 30 days after surgery. Other GDDs have valves to overcome this issue, but are less successful with maintaining long-term IOP. Our research goal is to improve NVGDD postoperative performance. Little rigorous research has been done to systematically analyze flow/pressure characteristics in NVGDDs. We describe an experimental system developed to assess the pressure drop for physiologic flow rates through NVGDD-like microtubes of various lengths/diameters, some with annular inserts. Experimental pressure measurements for flow through hollow microtubes are within predictive theory's limits. For instance, a 50.4 μm inner diameter microtube yields an average experimental pressure of 33.7 mm Hg, while theory predicts 31.0–64.2 mm Hg. An annular example, with 358.8 μm outside and 330.7 μm inside diameters, yields an experimental pressure of 9.6 mm Hg, within theoretical predictions of 4.2–19.2 mm Hg. These results are repeatable and consistent over 25 days, which fits the 20–35 day period needed for scar tissue formation to achieve long-term IOP control. This work introduces a novel method for controlling IOP and demonstrates an experiment to examine this over 25 days. Future efforts will study insert size and degradable inserts.

Commentary by Dr. Valentin Fuster
ASME J of Medical Diagnostics. 2018;1(4):041002-041002-10. doi:10.1115/1.4040470.

Skin thermal burn wounds are classified according to subjective assessments of wound depth that indicate divergent modes of medical intervention. However, clinically discriminating superficial partial from deep partial thickness burns remains a significant challenge, where only the latter requires excision and skin grafting. Motivated by the need for and ramifications of an objective burn wound assessment tool, this paper advances hyperspectral imaging (HSI) in a porcine skin burn model to quantitatively evaluate thermal burn injuries (superficial and deep partial thickness burns). Two-dimensional (2D) principal component analysis for noise reduction is applied to images captured by HSI in the visible wavelength range. Herein, a multivariate regression analysis is used to calculate the total hemoglobin concentration (tHb) and the oxygen saturation (StO2) of the injured tissue. These perfusion profiles are spatially mapped to yield characteristic distributions corresponding to the burn wound degree validated histologically. The results demonstrate that StO2 and tHb diverge significantly for superficial partial and deep partial burns at 24 h and 1 h, respectively (p < 0.05). A StO2 burn map at 1 h post-burn yields a 2D burn contour that is registered with a burn color image. This early stage burn-specific contour has implications to guide downstream burn excision and grafting.

Commentary by Dr. Valentin Fuster

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