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Case Study: Acute Ischemia
The color bar can be used to quickly identify
different regions of tissue oxygenation that then can be quantified
by using the HyperVu software. HT-oxy levels are related to color
changes (low to high, yellow to purple) – HT-deoxy levels
are related to brightness (low to high, pale to brilliant).
- 12 subjects, upper and lower extremity acute ischemia undertaken
to show the performance of HMOA in the assessment of tissue
oxygenation in a controlled low/no flow ischemia model in normal
volunteers.
- Total limb ischemia created with cuff above arterial pressure
on arm and leg
- HMOA measured during baseline, ischemia, reperfusion and late
recovery
- Baseline HT-Sat values were 35±10% and 35±11%
in the skin of the volar forearm and dorsal foot, and these
values decreased to 5±5% and 4±5% following total
occlusion. These values demonstrated a reperfusion overshoot
and then returned to baseline following release of the cuff.
HMOA measurements showed consistently lower tissue HT-Sat measurements
during ischemia compared to baseline and recovery states (p<.0001).
HMOA measurements could be correlated with TcPO2 measurements
(r2 = .76), but appeared to be more reflective of tissue oxygenation
status.
- Heterogeneity in tissue oxygenation as seen by HMOA explains
some of the variability in TcPO2 measurements seen in many literature
reports.
- This study successfully demonstrated a response to low-/no-
flow ischemic conditions measured by HMOA relevant in the quantitative
assessment of the degree and anatomic level of acute limb ischemia.
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