Speaker: Srinivasa Karthik (EE12S072)
Guide: Dr. Mohanasankar Sivaprakasam
Reconstruction surgeries in oncology and trauma often require transfer of a free flap, which is
anastomosed to restore its blood supply. Surgical errors and imperfections at the anastomosis site often
lead to thrombosis, resulting in flap necrosis within hours. To prevent this, the flap is intensely
monitored for the first 48 hours post-surgery. Current flap monitoring techniques are either invasive,
periodic or require careful interpretation of the observed parameters by an experienced evaluator, in
addition to being expensive due to technological complexity.
This work explores two wavelength reflectance photoplethysmography (PPG) as a potential
flap monitoring technique. The absolute value (DC) of the PPG is an indicator of net blood volume
and concentration changes according to Beer’s law. The pulsatile component of PPG is an indicator of
the presence of arterial flow. A prototype flap monitoring device and a custom optical sensor probe
were developed using inexpensive emitters and sensors. Thrombosis was simulated on a set of
volunteers by simple limb ischemia techniques. The DC, along with the pulsatile component of PPG
acquired with the device showed significant changes, confirming the ability to detect circulatory
disruptions and identifying the type – arterial or venous. Automating the thrombosis detection is
explored by way of sensitivity analysis.
The technique explored is real time, quantitative and cost effective, having a potential to be
used in monitoring free flaps post-surgery.