Abstract
Background/Need
Postoperative flap perfusion assessment methods still rely on the evaluation of traditional clinical indicators, which have the disadvantage of being subjective and burdensome.
Methodology
This study describes a self-designed infrared wireless thermometer for flap blood supply monitoring and evaluates its efficacy in the postoperative monitoring of 40 free flaps.
Device Description
The device consists of multiple temperature and humidity modules as well as a wireless module, which has the advantages of low cost and continuous remote monitoring.
Preliminary results
The alarm time of the wireless infrared thermometer was 30.5 ± 3.1 hours, and the clinical observation reported 41.7 ± 13.6 hours.
Current status
In future studies, the device will be tested on different types of flaps in a porcine model.
In reconstructive surgery, flap transplantation is frequently used to repair tissue defects. 1 In order to reduce the rate of flap necrosis, medical staff needs to monitor the perfusion of the flap after surgery to detect vascular crisis in time and treat it accordingly. Currently, most medical institutions still use the traditional clinical assessment method, which has problems such as discontinuous monitoring, subjectivity, and vulnerability to the external environment. 2 Therefore, blood supply monitoring devices that meet the needs of clinical practice are needed to circumvent the shortcomings of traditional monitoring methods.
The Wireless Infrared Thermometry Device
The wireless infrared thermometry device was developed by the Department of Hand and Microsurgery at the Affiliated Nanhua Hospital of the University of South China. The device consists of an Arduino microcontroller equipped with two Gy-MCU90614 infrared temperature measurement modules, a DHT11 temperature and humidity module, through the HC-12 wireless module communication(Figure 1A), PC terminal development of the upper software real-time access to data and the use of waveform graph visual display, and software set the blood flow obstacle alarm prompt function (Figure 1C). (A) Appearance of the wireless infrared temperature measurement device with each functional module. (B) The device is used for postoperative monitoring of the dorsal hand free flap. (C) PC software interface. Monitoring rate is once a second. The red line represents the flap temperature; the purple line represents the surrounding skin temperature; the green line represents the ambient temperature; the orange line represents the ambient humidity. A: DHT22 Module for measuring ambient temperature and humidity; B: GY-MCU90614 Module for measuring the temperature of the flap and surrounding skin; C: Main board and expansion board to control all functions of the device; D: Wireless transmitter module for sending all monitoring information via Bluetooth; E: Wireless receiver module Used to receive monitoring information and receive alarm signals remotely.
Proof of Concept in Clinical
The device group consisted of 20 patients after free flap surgery, and the flap blood supply was monitored using a wireless infrared thermometer. The implementation was simple: one temperature module was placed in the center of the flap and another temperature module was placed on the surrounding skin outside the attachment material and secured with medical tape. The module for measuring ambient temperature and humidity is fixed at the bedside (Figure 1B). Alarmed and recorded when the flap temperature drops 3 degrees compared to the surrounding skin temperature.3-5 The conventional group also consisted of 20 patients after free flap surgery. The blood supply of the flaps was monitored by an experienced microsurgeon following conventional clinical observation methods. The monitoring indexes included flap color, flap temperature, flap tension, and capillary filling test, and the flap was scored according to the above indexes. Statistical analyses were performed using SPSS (version:25.0). Paired samples t-test was used to compare the time required to determine blood supply disorders by two methods. P-value <.05 was considered statistically significant.
Results
Characteristics of the study participants.
Mean + SD for continuous variables: P value was calculated by weighted linear regression model. % for Categorical variables: P value was calculated by weighted chi-square test.
Differences in the effectiveness of clinician observation and the device in flap monitoring.
Mean + SD for continuous variables: P value was calculated by weighted linear regression model. % for Categorical variables: P value was calculated by weighted chi-square test.
Next Steps
In future studies, the device will be tested in different types of flaps in porcine models. In addition, there is no definitive definition of how much of a decrease in flap temperature from the initial level is considered vascular crisis, and this temperature value varies among flap types. 6 We hope to find a more accurate and reliable value in future studies with a large sample size of different flap types to further improve the accuracy of the wireless infrared thermometry to reduce the rate of flap necrosis.
Conclusion
In conclusion, we present a wireless infrared thermometry device for postoperative flap monitoring and validate its efficacy over conventional clinical monitoring methods in 40 patients after free flap surgery. The device has the advantages of being low-cost, noninvasive, continuously monitorable, remotely observable, and with automatic alarms.
Footnotes
Author contributions
Study concept and design: Xiongjie Huang, Mingjiang Liu, Ruijie Xie. Acquisition of data: Ruijie Xie, Qianlong Liu, Xiongjie Huang. Analysis and interpretation: Ruijie Xie, Ya Zhang, Mingjiang Liu. Study supervision: Mingjiang Liu, Xiongjie Huang. Writing the article: Ruijie Xie, Ya Zhang. Critical revision of the article: Mingjiang Liu, Xiongjie Huang.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was funded by The Clinical Medical Technology Innovation Guide Project of Hunan Province (2021SK51913), The General Project of Hunan Provincial Health Commission (20201985) and The Scientific Research Project of Hunan Health and Family Planning Commission (A2017018).
Ethical approval
The Ethics Review Board of the University of South China, the affiliated Nanhua hospital approved the protocol (No. 2021-ky-70). Informed consent was obtained from the patients themselves and, for minor patients, from their guardians.
