Pervasive wearable device for free tissue transfer monitoring based on advanced data analysis: clinical study report

Abstract

Free tissue transfer (FTT) surgery for breast reconstruction following mastectomy has become a routine operation with high success rates. Although failure is low, it can have a devastating impact on patient recovery, prognosis, and psychological well-being. Continuous and objective monitoring of tissue oxygen saturation (StO2) has been shown to reduce failure rates through rapid detection time of postoperative vascular complications. We have developed a pervasive wearable wireless device that employs near-infrared spectroscopy (NIRS) to continuously monitor FTT via StO2 measurement. Previously tested on different models, the results of a clinical study are introduced. Our goal for the study is to demonstrate that the developed device can reliably detect StO2 variations in a clinical setting: 14 patients were recruited. Advanced data analysis was performed on the StO2 variations, the relative StO2 gradient change, and the classification of the StO2 within different clusters of blood occlusion level (from 0% to 100% at 25% step) based on previous studies made on a vascular phantom and animals. The outcomes of the clinical study concur with previous experimental results and the expected biological responses. This suggests that the device is able to correctly detect perfusion changes and provide real-time assessment on the viability of the FTT in a clinical setting.

Keywords: breast reconstruction surgery; free tissue transfer; internet of things; near-infrared spectroscopy; spectroscopy; wearable device.

Fig. 1

Views of the ${\mathrm{StO}}_2$ device. (a) Top and bottom views of the electronic board of the device for continuous ${\mathrm{StO}}_2$ monitoring. (b) Top and bottom view of the patch-embodied device (left top and bottom pictures) coming with its charging station (right top and bottom pictures).

Fig. 2

Schematic representations of harvesting and suturing processes of the DIEP FTT operation for breast reconstruction following mastectomy.

Fig. 3

Setup of the ${\mathrm{StO}}_2$ patch-embodied device during the clinical trial. (a) Setup of the ${\mathrm{StO}}_2$ patch-embodied device on the cutaneous paddle of the FTT after breast reconstructive surgery. (b) Setup of the ${\mathrm{StO}}_2$ patch-embodied device on human excised discarded tissue—the piece of tissue excluded from the FTT is used to reconstruct the breast defect.

Fig. 4

${\mathrm{StO}}_2$ percentage and naive Bayes classification results using overall patients’ data. After time synchronization of all datasets, data are analyzed and processed. (a) ${\mathrm{StO}}_2$ percentage results using the combined datasets of all patients. (b) Combined ${\mathrm{StO}}_2$ results of all patients. (c) Naive Bayes classification using the combined ${\mathrm{hbO}}_2$ and HHb datasets of all patients.

Fig. 5

Fitted pattern of the average ${\mathrm{StO}}_2$ results of all patients with a 4-deg polynomial fit.

Fig. 6

The ${\mathrm{\Delta }}_{{\mathrm{StO}}_2}$ results from excised discarded tissue. Variations in the decay following excision of tissue are expected as clinical parameters, such as temperature and peripheral vasoconstriction, will vary from patient to patient regardless of weight of tissue excised, as well as the condition of the tissue prior to excision (i.e., there may be some relative ischemia given that the tissue was not planned to be used for transfer). BMI, body mass index; ST, skin tone. (a) The ${\mathrm{\Delta }}_{{\mathrm{StO}}_2}$ percentage results on human excised discarded tissue. Tissue weight = 460 g, patient age = 60, BMI = healthy, ST = 3. (b) The ${\mathrm{\Delta }}_{{\mathrm{StO}}_2}$ percentage results on human excised discarded tissue. Tissue weight = 80 g, patient age = 47, BMI = overweight, ST = 3.