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A Reflectance Photoplethysmography Based Technique to Detect Circulatory Disruptions

January 27, 2016 @ 2:30 pm - 3:30 pm

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.


January 27, 2016
2:30 pm - 3:30 pm
Event Category:


CSD 308


Mohanasankar S
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