Wireless MEMS sensor for monitoring pulmonary artery pressure

by John Williamson
Contributing Editor, MEMS Investor Journal

CardioMEMS, Inc. currently has its latest wireless MEMS device in clinical trials -- an implantable heart failure monitor designed to measure pulmonary artery pressure.  High pulmonary artery pressure is associated with fluid build-up in the lungs that occurs with the progression of heart failure.  It is a condition in which a weakened heart muscle cannot pump enough blood through the body that affects over 5 million Americans and is the leading cause of hospitalization in the United States.

Monitoring pulmonary artery pressure is a key element to control symptoms in the congestive heart failure patient, says Sandeep Yadav, CardioMEMS’ COO.  “Our MEMS based device is aimed at sensing pulmonary pressure increases in real time, enabling patients to transmit results directly to physicians via our proprietary website,” he says.

This schematic shows the flow of information from the implantable sensor to the external module and on to the office of the treating physician via a secure website.

MEMS based miniaturization of components was a key design concern along with biocompatibility, being unaffected by changes in body chemistry or biology and being radioopaque so that fluoroscopy can be used to observe sensor  emplacement.  “The device also takes into account altitude and atmospheric pressure changes, which can affect readings,” Yadav says. 

Components include the implantable sensor placed in the artery using a catheter procedure, and which is activated by RF energy transmitted from the external electronics module.  This is comprised of internal signal processing electronics, the antenna placed near the implant site to communicate with the sensor, and the graphical user interface that displays patient information.  This can be transmitted by patients from their home to a secure website.  Self-monitoring is done on a regularly scheduled basis or when patients are experiencing heart failure symptoms.

CardioMEMS developed custom circuitry to generate RF energy bursts that power the pulmonary artery pressure sensor, capture return signals and relay these to the microprocessor for storage.   Supporting the graphical user interface is a smart card reader to obtain sensor calibration data.  Alternatively, data can be entered manually by physicians.

Since the sensors are permanent implants, they were designed to be biocompatible, highly accurate and pressure stable over long periods of time. The advantage of the MEMS based approach is that the device is very sensitive to small changes in blood pressure yet is not affected by changes in the biologic environment surrounding the sensor, and thus does not require recalibration.

This pressure monitor follows CardioMEMS’ earlier announced abdominal aortic aneurysms pressure measurement system, also comprised of an implanted sensor and external module.  Future development includes a smaller version of the device that could be implanted in the wrist to measure hypertension.

Copyright 2010 MEMS Investor Journal

Comments

[sujeetsingh]

this is good for mems researchers , a new technology helping patients,,