Page 59 - Read Online

Cevallos et al. Plast Aesthet Res 2023;10:30 https://dx.doi.org/10.20517/2347-9264.2023.01 Page 7 of 17

[69]
Surface temperature monitoring has its limitations when applied to buried and intraoral flaps , and it can
be influenced by various external factors, including ambient room temperature and air flow. Research
suggests that in patients who have undergone DIEP breast reconstruction, surface temperature monitoring
using a dual-channel digital thermometer (Raytek, Norway) lacks sensitivity and is inferior to clinical
examination conducted by trained nurses . In the case of large perforator flaps such as DIEPs, the
[70]
temperature difference between the flap surface and adjacent non-flap surface may be minimal, reducing
the utility of surface temperature monitoring. However, it may still have value in monitoring perfusion in
[71]
scenarios like digit replantation and small free flap reconstruction .
Mobile smartphone monitoring technology
Given the widespread use of smartphones, leveraging this technology to enhance communication and
enable remote post-operative monitoring through adjunct devices presents a rapid, cost-effective, and non-
invasive option for early detection of free flap failure.

Innovative text messaging systems that alert surgical teams of post-operative monitoring tissue oximetry
readings below a certain threshold show promise in identifying potential flap loss and facilitating prompt
notification . With smartphones equipped with advanced digital photography capabilities, earlier
[72]
discharge and continued remote flap monitoring at home with improved communication between patients
and healthcare staff may soon become possible. Studies suggest that the use of remote digital photography
may even lead to reduced response time to re-exploration and improved flap salvage rates [39,73] . The
usefulness of digital photography by patients becomes even more apparent when uploaded through
[74]
dedicated post-operative monitoring platforms, enabling easy comparison with previous images . By
employing free applications on smartphones, continuous real-time streaming of free flap tissue to surgeons
for decision-making can be achieved . Kiranantawat et al. developed a smartphone application that
[75]
identifies color changes indicative of compromised flaps for monitoring purposes . Furthermore, the
[76]
integration of machine learning algorithms holds the potential to reveal previously undetectable findings to
the human eye .
[77]

Digital thermographic cameras, such as the FLIR ONE ™ device (FLIR systems, Wilsonville, Ore), can be
attached to a smartphone to capture thermal images of a free flap, enabling the detection of temperature
differences with high sensitivity. These images can be easily transmitted to healthcare providers for
evaluation and early identification of flap failure. While this device has primarily been used by trained
operators in the peri-operative setting for DIEP flap reconstruction, advancements in technology and
reduced costs hold the potential for future remote use by patients . However, it is important to note that
[78]
this device is influenced by external factors such as vasoconstriction, warming blankets, or low ambient
temperature, which may impact its accuracy.

Tissue oximetry
Tissue oximetry utilizes both near-infrared spectroscopy (NIRS) (wavelength: 800-2,500 nanometers) and
visible light (wavelength: 40-700 nanometers) to non-invasively measure flap perfusion [79-83] . Examples of
tissue oximeters commonly used in the post-operative setting include Spectros T-Stat (Houston, TX, USA)
and ViOptix T.Ox (Newark, CA, USA) [Figure 1A]. The functioning principle of most oximetry systems
follows a standard pattern: the oximeter devices emit light towards the flap tissue, a portion of which is
absorbed by the blood. The remaining light is reflected and captured by the sensors in the oximeter.
Oxygenated and deoxygenated blood reflect and emit light differently, and the oximeter probes utilize these
properties to estimate the percentage of oxygenated and deoxygenated hemoglobin within the underlying
tissue [13,69] . A decrease in tissue oxygenation detected by NIRS has shown high specificity and sensitivity in