Design Article
Streamlining the design of portable medical electronics
2/25/2011 5:46 PM EST
Electrocardiogram (ECG/EKG)
ECG is an interpretation of the electrical activity of the heart over time, captured and externally recorded by skin electrodes. It is measured non-invasively by capturing small voltages that are generated on the surface of the skin every time the heart beats.
Two leads are connected to the patient’s body for a single channel ECG and the voltage generated is the differential voltage of two connected leads. The range of the voltage is less than a millivolt in presence of large offsets and high noise from various sources of electrical interference.
The signal has to be amplified by an instrumentation amplifier, filtered, digitized, analyzed and stored for further processing and communication, Figure 3. The frequency range of interest in an ECG is typically between 0.05Hz and 150Hz. The microcontroller used to manage the signal chain can also be used to analyze the data captured.
Figure 3: Block diagram of electrocardiogram
Pulse oximeter
Pulse oximetry is a non-invasive method allowing the monitoring of the oxygenation of a patient's hemoglobin. The level of oxygenation of blood can be found (SaO2) based on the intensity of light attenuated by the body tissue. Oxygen saturation is the ratio of oxygenated hemoglobin to the total hemoglobin. Body tissue absorbs different amounts of light that is passing through it depending on the oxygenation level of the blood.
The system consists of a LED driver and a photo-diode, Figure 4. The output of the photo-diode is conditioned by programmable gain amplifiers and then digitized. This component will have an AC component and DC component. The AC component is a result of absorption by the arteries while the DC component is a result of absorption by tissues and veins. Analog components on PSoC can be used for this application. The external components include LED emitter, detector. The digital data obtained is stored in a non-volatile memory.
Figure 4: Block diagram of pulse oximeter
Next: (continued)
|
|
|
|
|
kinnar
2/28/2011 5:17 AM EST
It is really really very much required to have some iPhone kind of versatile device and platform for portable medical devices where functions of many devices can merged into one device and that too that device will be affordable upto an extent that it can be sold in every corner of the world, improving the local medical needs.
Sign in to Reply
prabhakar_deosthali
2/28/2011 7:07 AM EST
Such medical devices will be more appropriate for the developing world countries where the pathological laboratories are not too many and the cost of pathological analysis is very high. With affordable portable devices the people can do the routine health parameter checks on their own at much lower cost .
Sign in to Reply
agk
2/28/2011 10:50 AM EST
In a nut shell Cypress engineer's said about a home based basic patient monitoring system could be usefull to critically unstable healthy people. It is sure that Cypress PSoC's can be used efficienty in these applications.More information on these applications are available at Cypress website.
Sign in to Reply
Dr DSP
2/28/2011 5:03 PM EST
This is a good survey article with lots of high-level details. Look at some of the MCU guys websites for more detailed applications- even with code!
Sign in to Reply