Post-operative blood perfusion monitoring for free flaps surgery using a mini-pig model – FLAPS-MONITORING

Surgical reconstruction with free flaps is complex: a flap is taken from a healthy area of the body to be transposed into the damaged area. This operation requires microsurgical reconstruction of the vascular network. Tissue alterations may occur after such surgical reconstructions if the blood supply of the flap is not normal. They must be rapidly detected, surgically corrected as quickly as possible, otherwise the damage may be irreversible and extremely serious.

We propose a postoperative monitoring solution based on an optical device (laser probe, detection electronics) and a data processing method (2 patents). We have shown the relevance of the measures in rats, but these results have highlighted a difficulty in the quantification of deep vascular abnormalities. We propose to overcome this problem by making technical changes on the instrument and the reconstruction algorithm. We will test it on pigs which is a model representative of the common clinical situations. This will be the final stage of validation of this medical device before evaluation in humans.

Tissue oxygenation monitoring is very important in various clinical situations: tissue transplants, diabetic foot, vascular diseases (malformations, venous thrombosis…). FLAPS-MONITORING Project proposes a technological solution to monitor superficial and deep tissue oxygenation with a laser optical probe measuring up to 2 cm deep and in 3D the amount of blood in tissues and their oxygenation (via oxy/desoxyhemoglobine ratio). This in vivo measurement is continue, non-invasive without contrast agent injection. Currently there is no other system with such performance. Instrumentation associates an optical tool (laser, probe, and detection electronics) and a data treatment method (protected by 2 patents).
Surface measurement relevance was proven on a previous rat cutaneous flap model. This experiment identified a problem of vascularization quantification in deep measurements, partly due to the small size of the experimental model. Instrumentation and algorithm were improved.

FLAPS-MONITORING project aims to validate this new prototype on a porcine model, more representative of clinical situations. The data will be compared to the gold standard measure of tissue oxygen pressure with a LICOX probe. The other objective of this preclinical work is also to adapt the optical probe ergonomic (geometry, fixation…) for a future clinical use.

We are working on a patent application concerning the coupling DRS/TR.
The surgery protocol adapted to the porcine model has been submitted to the Journal of stomatology oral and maxillofacial surgery.

The FLAPS-MONITORING project aims at providing a technological solution to monitor the oxygenation of deep tissues.This is achieved with an optical laser probe capable of measuring the amount of blood present in the tissue, and to determine its oxygenation level (ratio oxyhemoglobin / de-oxyhemoglobin). This is accomplished in 3D at up to 2cm depth, non-invasively, directly in vivo, without contrast agent injection. The measurement can be performed continuously for several days. There is currently no device capable of such performance.

Monitoring tissue oxygenation is particularly important in several clinical applications such as breast surgery, diabetology for the management of the "diabetic foot", monitoring of cutaneous angiogenesis and other vascular problems (angiomas , arteriovenous fistulas and aneurysms, deep vein thrombosis) ...

The FLAPS MONITORING project aims at finalizing a prototype we have already manufactured. In the present study, we will test it on a particular issue that are "free flaps" in a pig model of buried flaps.

Surgical reconstruction with free flaps is complex: a flap is taken from a healthy area of the body to be transposed into the damaged area. This operation requires microsurgical reconstruction of the vascular network. Tissue alterations may occur after such surgical reconstructions if the blood supply of the flap is not normal. They must be rapidly detected, surgically corrected as quickly as possible, otherwise the damage may be irreversible and extremely serious.

We propose a postoperative monitoring solution based on an optical device (laser probe, detection electronics) and a data processing method (2 patents). We have shown the relevance of the measures in rats, but these results have highlighted a difficulty in the quantification of deep vascular abnormalities. We propose to overcome this problem by making technical changes on the instrument and the reconstruction algorithm. We will test it on pigs which is a model representative of the common clinical situations. This will be the final stage of validation of this medical device before evaluation in humans.

This project is made possible through the close collaboration between the CEA-LETI group that develops technology, and the group of INSERM U823, which implements the device in pre-clinical and clinical applications. Both groups are used to work together and several devices are being marketed already, including by the Fluoptics company, co-created by these two groups. Medical and surgical expertise is provided by Prof. Georges Bettega, a specialist in maxillofacial surgery, coordinator and promotor of this project that may change significantly his practice of surgery. The VetAgroSup Lyon group will also help us and provide the surgical room and competences for the management of 20 pigs included in this study.