优秀毕业设计（论文）：数字式脉搏血氧仪设计

毕业设计(论文)

数字式脉搏血氧仪设计

系 别 专 业 班 级 姓 名 指导教师

自动化工程系 生物医学工程

50616 常衍春 贺忠海

2010 年 6 月 10 日

东北大学秦皇岛分校毕业设计（论文） 第I页

摘 要

脉搏血氧仪是一种可连续、无创、方便地检测动脉血氧饱和度的仪器。由于其在系统设计和信号处理方法上存在的缺陷,使它在测量的精度、重复性、稳定性等方面还存在需要探讨和完善的地方。本课题提出了基于动态光谱的脉搏血氧测量原理，并且在该原理的指导下，设计了一套数字化脉搏血氧检测系统。系统采用纯数字芯片设计，提高了系统稳定性和重复性。系统采用数字滤波和数字解调的方法，用软件提取光电脉搏波信号。并在动态光谱原理基础上，根据推导出的算法，获得了高精度的脉搏血氧饱和度测量值。

本课题的创新与主要工作体现在以下方面：

（1）通过分析传统脉搏血氧测量原理引起的测量误差，在理论上推导出实现高精度脉搏血氧测量的方法——基于动态光谱方法的脉搏血氧测定法，这种方法在原理上可以消除由于测量条件及个体差异等多方面因素对测量精度的影响。

（2）针对传统的脉搏血氧饱和度检测系统中因模拟电路复杂而引起的系统稳定性和重复性差的问题，本文提出了数字化的设计思想，根据动态光谱测量原理采用现代微处理器、集成电路技术，设计了脉搏波信号的检测、采集及处理系统。提高了系统稳定性和可重复性，降低了由于模拟电路不稳定所造成的系统测量误差。

（3）采用数字解调的方法对采样的数字信号解调为双路光信号，并用软件提取光电脉搏波。在动态光谱理论的基础上，对光电脉搏波信号进行时域频域转换，所得到基波分量用于血氧饱和度计算，获得了高精度的脉搏血氧饱和度测量值。

本系统在硬件方面设计了以MSP430为核心的信号检测和采集系统，并结合了双波长频分法和过采样技术，在提高分辨率和信噪比的同时，大大简化了硬件电路。并利用数字滤波和数字解调的数据处理方法，完成双路信号分离。研究了容积脉搏波的软件提取和检出，并在通过傅立叶变换得到光电脉搏波的基波分量，用于血氧饱和度计算。

关键词：血氧饱和度，脉搏血氧测定法，动态光谱，硬件设计，软件设计

东北大学秦皇岛分校毕业设计（论文） 第II页 Digital pulse oximeter design

Author：Chang Yanchun

Tutor：He Zhonghai

ABSTRACT

Pulse oximetry is a reliable, arterial, noninvasive easy continuously determining oxygen saturation to use means in virtually of any setting. Because there are still several drawbacks in the design of the pulse oximetry system and its signal processing, the system needs improving in accuracy, repetition and stability. This system is proposed based on dynamic spectroscopy measuring principle, and in this principle, under the guidance of a set of digital pulse oximetry test system. System adopts digital chip design to improve the system stability and repeatability. System using digital filter and digital demodulation method, using photoelectric pulse wave signal extracted by software. And with dynamic spectroscopy, based on the principle of the algorithm is deduced, the pulse of the high-precision measurements oxygen saturation. This subject mainly embodies the innovation and work in the following respects: First, the measuring principle of the pulse oximeter is based on traditional test method. Its accuracy is not gratifying due to various factors influencing the measurement result, such as the principle, measuring condition and individual discrepancy. In this system a new pulse oximetry based on dynamic spectroscopy (DS) is introduced, it can promote the accuracy of the pulse oximeter evidently. The dynamic spectroscopy method is able to eliminate the interference of the individual discrepancy and measuring condition in principle. This new method can eliminate the measurement error of pulse oximetry theoretically.

Secondly the pulse of the traditional testing system of oxygen saturation because of complex analog caused poor stability of the system, this system puts forward the design thought according to the digitization of dynamic spectroscopy measurement principle adopts modern microprocessor, integrated circuit technology, the design of the pulse wave signal detection and collection system. We use the microprocessor driven directly by certain wavelengths of light emitting diode; receiving tube will receive light signals into electrical signals, high frequency converter by the direct current, pulse wave signal carry photoelectric instead of digital signal, the hardware circuit and AC drive circuit source separation circuit. Reuse digital filter to replace filter circuits, analog circuits to save a part of signal and system

东北大学秦皇岛分校毕业设计（论文） 第III页

this filter system stability and repeatability, reduced due to the instability of analog circuit is caused by the measurement error of the system.

Finally, using digital demodulation method to sample signal demodulation of digital signal, the dual light for extracting photoelectric pulse wave by software. On the basis of the theory of dynamic spectroscopy, conversing photoelectric pulse wave signal from frequency to division and the component be used in the blood oxygen saturation calculation.

In this system, the hardware design MSP430 as the core to signal detection and collection system, combining with the dual wavelength frequency division method of sampling technology and in improving the resolution and signal-to-noise ratio, greatly simplified the hardware circuit. Use digital filter and digital demodulation of the data processing method to double signal separation. Study the volume of pulse wave extraction from the software, and through a Fourier transform of photoelectric pulse wave get component for the blood oxygen saturation.

KEY WORDS： Oxygen saturation, pulse oximetry, dynamic spectroscopy, hardware design, software design

东北大学秦皇岛分校毕业设计（论文） 第IV页

目 录

1 绪 论 ........................................................................................................................ 1

1.1 血氧饱和度的概念及其生理意义 ................................ 1 1.2 脉搏血氧饱和度测量仪的发展历程 .............................. 2 1.3 脉搏血氧饱和度测量仪的现状 .................................. 3 1.4 本系统的研究意义及主要内容 .................................. 4 2 脉搏血氧饱和度的测量理论基础及动态光谱理论 ................................................ 6

2.1 光电容积脉搏波的产生原理 .................................... 6

2.1.1 脉搏波的产生原理 ...................................... 6 2.1.2 光电容积脉搏波描记法（PPG）原理 ....................... 7 2. 2 脉搏血氧饱和度测量的理论基础与算法 ......................... 8

2.2.1 郎伯－比尔(Lambert-Beer)定律及应用 .................... 8 2.2.2 离体血氧饱和度测量原理 ................................ 9 2.2.3 传统脉搏血氧测定法 ................................... 12 2.3 基于动态光谱的脉搏血氧检测原理 ............................. 13

2.3.1 修正的朗伯－比尔定律 ................................. 13 2.3.2 动态光谱理论 ......................................... 13 2.3.3 基于DS的脉搏血氧测量原理 ............................ 14 2.3.4 基于DS的脉搏血氧算法与传统算法精度比较 .............. 15

3 基于DS的脉搏血氧检测系统的数字化实现方法 ................................................ 17

3.1 传统脉搏血氧仪测量系统回顾 ................................. 17 3.2 基于DS的脉搏血氧测量系统的系统硬件组成 .................... 18

3.2.1 总体设计思想与系统构成 ............................... 18 3.2.2 基于MSP430系统平台的外围电路设计 .................... 19

3.2.2.1 光源及其驱动电路的设计 .......................... 19 3.2.2.2 电路板及各芯片的电源设计 ........................ 22 3.2.2.3 串口设计及外USB座的设计 ........................ 23 3.2.2.4 外接存储设备设计及锂电池充电管理设计 ............ 24 3.2.2.5 液晶模块及其驱动电路设计 ........................ 26 3.2.3 基于MSP430平台系统的设计 ............................ 26 3.3 基于DS的脉搏血氧仪的数字化测量方法 ........................ 31

3.3.1 双波长频分测量法及信号的数字解调 ..................... 31

4 系统软件设计 .......................................................................................................... 34

4.1 Embedded Workbench开发平台和调试器C-SPY的简单介绍 ....... 34 4.2 初始化程序 ................................................. 35 4.3 主程序设计 ................................................. 37 4.4 按键和显示程序设计 ......................................... 39 4.5 系统误差分析 ............................................... 41 总结 ................................................................................................................................ 43

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