Preliminary findings from an initial study with 25 patients have shown that measuring the changes in oxygen concentration at baseline, during, and after endovascular revascularisation, can predict wound healing and functional improvement in critical limb ischaemia patients.
Marianne Brodmann, Medical University Graz, Austria, presented the initial OMNIA study results that used the Lumee oxygen platform (Profusa) as a unique tool to assess and clinical management of critical limb ischaemia patients at the Leipzig Interventional Course (LINC; 30 January–2 February 2018, Leipzig, Germany). The platform is designed to provide immediate feedback on the quality of revascularisation and along the entire course of the patient’s recovery. It uses hydrogel sensors that are injected into the skin of the patient that measure the oxygen concentration in the tissue.
Assessing procedural success in a complex critical limb ischaemia setting is challenging. “When it comes to critical limb ischaemia, we all still struggle with an objective assessment in the management of these patients,” said Brodmann.
OMNIA (Oxygen monitoring near ischemic areas) is a prospective, single-arm, open label, multicentre study designed to understand the relationship between revascularisation success, traditional measures of gross haemodynamic characterisation and Lumee measurement of tissue perfusion. Data were captured to establish feasibility and generate a hypothesis.
Through end of 2017, 21 patients—all Rutherford class five and most who were diabetic—had been enrolled. All but two received endovascular treatment, whilst the others had bypass surgery, after attempted endovascular therapy.
Four Lumee sensors were injected into each patient; three in the foot and one as a reference sensor in the arm. Measurements were performed continuously during the functional assessment tests performed before and after revascularisation, during the endovascular revascularisation procedure at one, three and six months at follow-up visits, explained Brodmann. Traditional clinical metrics sampled throughout visit schedule included arterial duplex, toe and ankle-brachial index (ABI), wound, ischaemia, and foot infection (WIfI) scores, wound characterisation and photographs.
Commenting on the information extracted from Lumee intrasurgically, Brodmann said: “This is called reperfusion modulation, which is defined as the difference in Lumee Oxygen Index (LOI) between baseline and maximum after intervention. Larger values are associated with greater increases in tissue oxygen during the procedure and this data can be averaged across all Lumees or selected from a Lumee of interest”.
Changes in LOI measured during endothelial revascularisation were found to be predictive of wound healing. Describing a case when the endovascular procedure was successful and flow was re-established to the foot, investigators obtained a LOI change that was high. Later functional assessment was positive and the patient’s wound decreased in size, the ankle-brachial index increased and the patient’s Rutherford category changed.
In another case when endovascular treatment was unable to re-establish flow, ie, in a non-responding patient, the LOI change was very low and later functional assessment and follow-up established that the wound did not heal, but that wound area increased.
“These results show that larger increases in LOI were associated with wound healing in our patients. When we observe LOI changes that are larger than 10, this predicts wound healing (as seen in 5/6 patients). When we observed oxygen index changes of less than zero, this predicted non-response, and we saw this in the two subjects who later underwent bypass surgery,” said Brodmann.
“There were 50 adverse events reported, of which 27 were serious and all unrelated to the study device. There were also 23 minor adverse events, of which 22 were unrelated to the study device. There was one mild swelling that resolved at follow-up that was possibly related to the device,” said Brodmann.