Portable pulse oximeter complete design

I. Project Overview

1.1 Introduction

Blood oxygen saturation (SaO2) is a physiological parameter for measuring the oxygen carrying capacity of human blood and is of great significance in clinical diagnosis. The measurement method of blood oxygen saturation can be divided into invasive measurement and non-invasive measurement. Invasive measurement method is to first collect blood from the human body, and then use the blood gas analyzer to perform electrochemical analysis, measure the partial pressure of hemorrhage oxygen PO2, and calculate SaO2. This method is cumbersome and cannot be continuously monitored. The non-invasive measurement mainly adopts the double beam transmission method, and the ratio of the relative change values ​​of the absorbance of the biological tissue by the red and infrared light of different wavelengths is estimated as SaO2.

Since biological tissue is a complex optical system with strong scattering, weak absorption, and anisotropy, it does not completely conform to the classical Beer-Lambert absorption law, which results in the ratio of the relative change in absorbance of red and infrared light (R/IR). The relationship between the value and arterial oxygen saturation (SaO2) can only be approximated using a mathematical model. At the same time, the error caused by the non-ideality of the light source generated inside the non-invasive pulse oximeter also makes the measurement accuracy generally lower than the accuracy of the invasive measurement. This design has carried out in-depth research on the above problems, and proposed a design scheme of a new non-invasive portable pulse oximeter. It can be proved that the pulse oximeter developed by this design can improve the measurement accuracy of blood oxygen saturation.

1.2 Project Background / Motivation

Sufficient oxygen supply is the basis of life. Arterial oxygen saturation is an important parameter reflecting blood oxygen. Its measurement is of great significance in clinical medicine. Although the Vansler method is effective for accurate measurement of blood samples, the method cannot be continuously monitored, and the measurement process is cumbersome, which brings great inconvenience to the medical staff and brings pain to the patient. The pulse oximeter Pulse oximeter has the function of non-invasive, continuous, rapid and accurate monitoring of arterial oxygen saturation SaO2. It has been recognized by the medical community and entered clinical application, especially for surgical monitoring of critically ill patients. Pulse oximeters are widely used in operating rooms, recovery rooms, emergency wards, and physical exercise and sleep. The AVR32 family of microcontrollers offers low power consumption and high analog performance. Application on single-chip portable medical instruments has great advantages. The number of peripheral components of the product can be minimized. In this design, the power consumption can be further reduced by controlling the turn-on time and operating frequency of the LED lamp, so that the entire system achieves ultra-low power consumption and is environmentally friendly.

Second, the demand analysis

2.1 Functional requirements

Parameters such as blood oxygen saturation and heart rate are collected by an external optical probe and displayed on the LCD. The optical probe consists of two LEDs, one is a visible red LED and the other is an infrared LED. The probe can be placed at the tip of the finger or the earlobe. When the two LED lights pass through the body, the MCU calculates the blood oxygen content in the human body by detecting changes in the two light intensities. When the blood oxygen concentration and heart rate in the human body are lower than a certain set value, the oximeter can issue an alarm signal to prompt the user. The system architecture is shown in Figure 1:

Figure 1 System Architecture

2.2 Performance requirements

● Measurement method: dual wavelength measurement;

●Value display: large screen LED or LCD display, SaO2, pulse value is clearly visible, not subject to ambient light, suitable for various first-aid places;

● Pulse display: three-color analysis system, LED quickly displays pulse quality;

● Measurement range: blood oxygen saturation: 0-100% heart rate: 18-300 beats / minute;

● Measurement accuracy: blood oxygen saturation: ± 1S. D heart rate: ± 3%;

●It can connect probes for adults, children and newborns;

● It can store data, fast and sensitive SaO2 value, suitable for sleep analysis and communication with PC via USB and other communication parties

● can display current time, temperature and other information;

● Battery powered: six AA batteries, can work continuously for more than 24 hours.

Power: 220V-240V 50/60Hz  1200W, Motor : Dual driving       

9.Unique dough hook & mixer whisk are included.                                

 10.Low noise, environment friendly                                               

11.Cord length: 1.2m

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