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Allam et al. Plast Aesthet Res 2024;11:19 https://dx.doi.org/10.20517/2347-9264.2024.21 Page 9 of 16

[50]
vascular compromise increases the likelihood of flap salvage .

Current methodologies rely on clinical evaluation of flap perfusion to identify flaps at risk for failure. This
includes examining flap color, capillary refill, skin temperature, and tissue turgor, as well as handheld
Doppler signals. However, much of this evaluation remains subjective, and its accuracy varies among
different skin types, highlighting the role of a more objective evaluation method. In addition, clinical
evaluation can be time-consuming, requiring frequent evaluations to allow for early intervention, resulting
in substantial provider burden, especially in the immediate postoperative period .
[50]

Recent advances in the field of flap monitoring have been made to increase its objectivity and efficiency.
This includes the development of remote patient monitoring platforms to decrease provider burden and the
advancement of tissue oximetry technology to assess perfusion more accurately [50-52] .

Remote patient monitoring platforms
Flap monitoring, especially critical within the first 72-h window, is a cornerstone of postoperative
management in autologous reconstruction and has been strongly associated with the success of flap
revisions . Remote patient monitoring has emerged as a time-efficient and effective alternative to
[53]
[50]
traditional in-person monitoring . In the realm of autologous breast reconstruction, Hummelink et al.
piloted a wireless monitoring sensor based on Imec’s Nightingale system (Eindhoven, the Netherlands) for
DIEP flaps, featuring real-time data transmission capabilities to smartphones (although this function was
disabled during the pilot study). The red and infrared sensors, equipped with two probes for placement on
the flap and healthy skin tissue [Figure 4A], measured multiple parameters including temperature, tissue
oxygenation, and delta muscle saturation every 90 seconds . Similarly, Xie et al. developed an infrared
[51]
wireless thermometer for flap perfusion monitoring, incorporating temperature and humidity modules
along with a wireless component for remote monitoring. The device was able to recognize signs of
decreased perfusion much earlier compared to conventional clinical techniques (30.5 vs. 41.7 h) .
[54]
Additionally, to counter the traditional cabled Cook Doppler (Bloomington, Indiana) monitoring device,
Oda et al. created an implantable wireless and biodegradable sensor for real-time monitoring over the
anastomosis site, lasting over a week. In a feasibility animal study in rats, the biosensor was implanted
around the femoral artery, showing no significant differences in arterial lumen diameter, intima thickness,
or tissue inflammation indicator compared to the control group. The sensor also detected changes in
femoral arterial signals immediately following venous occlusions . However, these promising results in
[55]
animal models await validation in human trials.

Remote patient monitoring presents significant potential to revolutionize postoperative monitoring
strategies. Nevertheless, further research is essential to refine and standardize this innovative approach,
ensuring its efficacy and reliability in clinical settings.

Advanced tissue oximetry technology
Tissue oxygenation has historically been identified as a key parameter for assessing postoperative flap
perfusion . While peripheral tissue oxygenation measurements have demonstrated poor accuracy when
[56]
predicting flap failure, recent in vivo studies and human trials have introduced novel strategies to accurately
measure and correlate tissue oximetry to tissue perfusion [52,57] . Currently, the most prevalent and reliable
optical method for monitoring flap perfusion through tissue oximetry is the ViOptix (Fremont, Calif.) T.
OX system, which utilizes near-infrared spectroscopy (NIRS). Nevertheless, this system's reliance on cabled
[58]
leads connected to a control unit can be cumbersome, restrictive, and uncomfortable for patients . These
[59]
systems are also known to trigger false alarms due to many inevitable factors such as patient movement .
Addressing these challenges, the novel ViOptix Intra.Ox handheld device was developed for more accurate