1. `
Integration of Pressure Sensors in a Compression Garment For The Treatment of Hypertrophic
Scars.
Zachary M. Llaneras, Jorge L. Calderon, Ahmed Jalal, Patrick A. Roman, Shekhar Bhansali, Jessica C. Ramella-Roman
Medical Photonics Laboratory, Department of Biomedical Engineering and Herbert Wertheim College of Medicine, Florida International University
Abstract
Limited evidence exists on the efficacy of compression therapy
due to the lack of measurements of hypertrophic scar severity,
inability to quantify pressure applied to scars, as well as the lack
of wearable, self-operated devices capable of monitoring
pressure in real time. MEMS based pressure sensors are
piezoresistive silicon pressure transducers with high
performance and small footprint, their adaptation for biomedical
use has been shown by other investigators and will be
implemented by our group for the smart compression garment.1
Our goal is to construct a clinically applicable non-invasive
compression garment that is able to wirelessly provide a real
time measurement of pressure to patients and clinicians.
Background
Compression therapy is a widely used treatment to prevent the
formation of hypertrophic scars, regularly performed with
compression devices, bandages, and garments made from
elasticized fabrics, Fig. 11. By applying a controlled amount of
pressure to the target tissue, superficial perfusion can be
controlled leading to a reduction in blood oxygenation. The
balance between collagen synthesis and collagen lysis is
delicate, a reduction in tissue oxygenation leads to a lower
collagen production while maintaining constant lysis.
Compression garment are used to control this production/lysis
balance3. Nevertheless excessive or deficient pressure can give
negative results or lead to tissue damage in patients. Hence
monitoring exerted pressure is critical. Here we proposed the
creation of a smart compression garment, where a MEMS based
pressure sensor is used to monitor the applied pressure in real
time. The value of pressure is relayed wirelessly to a measuring
station.
Methods
The smart compression garment was based on the MS 1451
(Measurement Specialties), a low profile, air pressure sensors
utilizing MEMS technology. The original casting of the sensor
was removed and wires were soldered onto it. Then the sensor
was embedded in a < 1mm thick sealant gel and cured for 24
hours. Power and communication with the sensor was
conducted with a wired connection, and sensor data was
transferred by direct connection to a very low profile Arduino
board. Calibration of the sensor was performed with known
pressure values obtained from a pull tester (ADMET). Software
communication was established with a data station so that
pressure was monitored in real time.
Results
Calibration of the compression garment showed a robust linear
behavior in the range of interest (10-60 mmHg). The sensor was
capable of repeatable pressure measurement with error well
below 0.3%. Steady state measurement of pressure showed no
noticeable drift in the measurement and negligible hysteresis.
Conclusions
Compression garments are made of elastic materials that tend
to lose elasticity over time. The therapeutic effect of the garment
is then reduced, a fact that may go unnoticed for weeks until
routine checkup is conducted. With the smart compression
garment proposed here, physicians could monitor the applied
pressure in real-time and prescribe garment adjustments if
necessary.
Fig. 1 Model of a hand-sleeve compression garment
Fig. 2 Schematic of electronics and control unit for the smart
garment
Ultimately the board and the sensors where integrated into the
compression garment.
Tests were conducted to ascertain the sensor limitations and
included noise measurement in a steady-state condition, and
during common activities that required garment motion.
Fig.3 Sensor realization
Fig. 4 Calibration curve for sensor
Fig. 6 Typical values obtained for different values of applied
pressure
Fig. 5 Hysteresis curve
Wireless communication to a computer station could be
established up to 20 meters range in open space and
provided immediate feedback to the user.. While the
sensor was integrated into the glove, it could accurately
read the applied pressure from a relaxed to an active
state.
References
1 V. Casey, P. Grace, and M. Clark-Moloney, “Pressure Measurement at Biomedical
Interfaces,” Applied Biomedical Engineering, 240–256 (2011).
2 P. Ghassemi, J.W. Shupp, T.E. Travis, A.J. Gravunder, L.T. Moffatt, and J.C. Ramella-
Roman “A Portable automatic pressure delivery system for scar compression therapy in
large animals,” (AIP). (2014)
3 L. Macintyre and M. Baird, “Pressure garments for use in the treatment of hypertrophic
scars—A review of the problems associated with their use,” Burns 32(1), 10–15 (2006).