Development of a pulse oximeter, measuring blood oxygen and heart rate with LCD display

ABSTRACT

The article provides data on the developments that are underway in Uzbekistan for the production of a pulse oximeter device corresponding to local climatic conditions, describes its characteristics and methods of use, electrical circuits, as well as measured parameters.

АННОТАЦИЯ

В статье приводятся данные, о разработках, которые ведутся в Узбекистане по выпуску устройства пульсоксиметр, соответствующего местным климатическим условиям, описывается его характеристики и способы пользования, электрические схемы, а также измеряемые параметры.

Keywords: TIDA-010029, climatic conditions, PPG probe, switching circuit and LED driver, AFE4420 chip.

Ключевые слова: TIDA-010029 ,климатические условия, пробник PPG, схема переключения и драйвера светодиода,AFE4420 чип.

Life is the most expensive and valuable currency that any state can be proud of. And the health of its people is an integral part of the well-being of any nation.

On the medical equipment market in Uzbekistan, you can currently see many devices designed to measure the level of oxygen in the blood and monitor oxygen saturation of the whole body.

But all companies that provide this equipment do not take into account the specifics of the climatic zone of this state.

Due to the fact that according to international statistics in Uzbekistan during the summer months the temperature in some areas reaches + 40- + 50 degrees, the devices may fail, and the case may heat up and malfunction, at the Islam Karimov Technical State University a special case for the pulse oximeter is being developed, which will correspond to the climatic conditions of this state.

The elements of the TIDA-010029 project (Fig. 1) by Texas Instruments are taken as a basis, which implements many types and types of pulse sensors measuring the oxygen content in the blood with various functionalities.

Figure. 1. TIDA-010029 - development of a wireless non-contact pulse oximeter with BLE interface

The AFE4420 chip is the main hardware part. The wireless interface of the handheld sensor is one of the most preferred option for the end user, this feature allows the user to monitor the sensor readings in real time and monitor the readings.

This is a single-chip photoplethysmography (PPG) measurement device. The 16 different light-corrected measurement combinations are possible with the AFE4420, as the AFE4420 supports up to four LEDs and photodiodes. CC2640R2F is a crystal-based system that wirelessly transmits measured data for further processing. This type of device is powered by a CR3032 battery.

On the example of this company, research is underway to increase the number of LEDs and photodiodes to six, which will allow up to 64 different combinations with backlight correction.

In this structure, the dominant parameter is the correct placement and connection of photodiodes and LEDs on the microcircuit.

Having considered the two main connections of more than one LED and a photodiode, you can make the correct connection-series, in such an aspect as the main parameter of the LED is its operating current, which determines the power of the LED (Fig.2).

Figure 2. Series connection of LEDs

Exceeding the parameters of the maximum current can lead to burnout of the LED, since the temperature of the crystal will be maximized, which will lead to overheating.

Therefore, the problem in these studies is the development of a microcircuit that will correspond in power to a given number of LEDs and photodiodes. At the same time, it should be compact, since the pulse oximeter should be as compact as possible and should be easy to handle.

References:

1. TIDA-010029 Wearable, 16-phase multi-sensor SpO2 and heart rate monitor (HRM) reference design with Bluetooth® 5 _ TI.com. 
2. Design Guide: TIDA-010029 Wearable, 16-phase multi-sensor SpO2 and heart rate monitor (HRM) reference design with Bluetooth® 5.
3. R.S. Khandpur,  ISBN10:0-07-047355-2 “Handbook  of  Biomedical Instrumentation  ”,  Tata  Macgraw-Hill Education,  April  1,  2003, second edition.
4. Saly J.  2000. Neonatal  and Pediatric  Pulse Oximetry.  Respiratory Saturation And  Heart Rate  Monitoring Device”,  pp 9-25, April 10, 2009.
5. Y.  Iyriboz  ,  J.  Morrow  ,  D.  Ayers  MS  and  G.  Landry  MS, Accuracy  Of Pulse  Oximeters In  Estimating  Heart  Rate At  Rest And During Exercise” vol 25(3), pp 152-164,September, 1991