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Subcutaneous oxygen biosensor shows promise for patients with CLI
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An injectable tissue-integrated biosensor with an intelligent data platform successfully measured changes in tissue oxygen levels in humans and may provide information that predicts outcomes after endovascular revascularization in patients with critical limb ischemia, according to two studies presented at the Leipzig Interventional Course.
In a feasibility study, Peter A. Schneider, MD, vascular surgeon and chief of the vascular therapy division at Kaiser Foundation Hospital, Honolulu, and colleagues compared tissue oxygen levels measured using the subcutaneous biosensor (Lumee oxygen platform, Profusa) with levels measured by a transcutaneous oximetry device.
The researchers injected the biosensor in the forearms of seven healthy volunteers and used a pressure cuff to simulate an occlusion by inducing circulatory interruption in the upper arm. Vascular occlusion tests included 15 minutes of warm-up, 5 minutes at baseline, 2 minutes during pressure-cuff occlusion and 10 minutes of recovery. The test was repeated twice per visit. Oxygen measurements were simultaneously recorded using the biosensor platform and a transcutaneous oximetry device.
Repeated tests occurred from 1 to 10 weeks after implantation and 95 artifact-free occlusion samples were included in the analysis.
Both the biosensor platform and the transcutaneous oximetry device sensed a decrease in oxygen levels during occlusion (P < .001 for each device), with no significant differences observed between the devices. Results also showed that the biosensor platform, as compared with the transcutaneous oximetry device, detected faster rates of oxygen change during the occlusion and recovery phases (Wilcoxon signed-rank test, P < .001); reactive hyperemia in more tests (38% vs. 4%); and larger fluctuations (Wilcoxon signed-rank test, P < .001).
“Measurements of regional tissue oxygen serve as a proxy to monitor local perfusion and have the potential to guide crucial therapeutic decisions in multiple clinical disciplines for peripheral artery disease ... and wound management that are now made on the basis of clinical judgment and experience alone without guidance,” Schneider said in a press release.
The biosensor platform also yielded positive data in an interim analysis of the first 30 patients with CLI enrolled in the ongoing, prospective, open-label, single-arm, multicenter OMNIA study.
In OMNIA, Marianne Brodmann, MD, interim head of the clinical division of angiology, department of internal medicine at Medical University in Graz, Austria, and colleagues continuously measured tissue oxygen levels using the biosensor platform during endovascular revascularization procedures; during functional assessment tests performed before and after revascularization; and at follow-up.
Patients were injected with three biosensors in the foot and one reference sensor in the upper arm.
The researchers found that tissue oxygen changes measured by the biosensor platform positively correlated to changes in toe-brachial index. Additionally, based on wound healing at 3-month follow-up in 28 patients, results showed that the median oxygen increase measured by the biosensor platform in patients who showed improvement was greater than the median increase in patients who did not improve (one-way rank sum test, P < .035).
In an exploratory receiver-operator characteristic analysis, increases in tissue oxygen level measured by the biosensor platform were predictive of wound healing. However, changes in toe-brachial index before and after revascularization were not as able to predict treatment outcome, according to the data.
“We are pleased to see that continuous monitoring of extravascular tissue oxygen using the Lumee oxygen platform showed a positive correlation to [toe-brachial index], demonstrating that this technology could be useful to help guide clinical choices during CLI management,” Brodmann said in the release. “These data also validate previous research that showed increases in oxygen during revascularization may be a sensitive indicator of wound healing following the procedure.” – by Melissa Foster
References:
Brodmann M. Innovation forum – PVD-SFA/BTK.
Schneider PA. Disruptive treatment approaches and pioneering techniques for patients with vascular disease. Both presented at: Leipzig Interventional Course; Jan. 22-25, 2019; Leipzig, Germany.
Disclosures: Brodmann reports she has financial ties with Bard Peripheral Vascular, Bayer Healthcare, Biotronik, Intact Vascular, Medtronic, Philips/Spectranetics, Reflow Medical, Sanofi, Shockwave Medical, Veryan, VIVA Physicians and W.L. Gore and Associates. Schneider reports he has consulted for CSI, Profusa, Silk Road, Surmodics and Terumo; he is chief medical officer of Cagent, Intact Vascular and Vesper; and he serves on the scientific advisory board for Abbott, Boston Scientific and Medtronic.