三波长血氧饱和度定标曲线的研究

目的 研究三波长血氧饱和度定标曲线,为自主研发的三波长肝脏储备功能检测仪提供准确的血氧饱和度计算公式.方法 首先运用Beer-Lambert定律推导出脉搏血氧饱和度(SpO2)与吸光度(R)的关系式;然后以课题组自主研发的三波长(660 nm,805 nm,940 nm)无创肝脏储备功能检测仪为实验设备,进行5例样本的动物实验,记录SpO2与R构成的数据点,并通过该数据点建立以SpO2与R的关系式为拟合依据的三波长血氧饱和度经验定标曲线与公式;最后将测试得到的血氧饱和度表达式应用于三波长肝脏储备功能检测仪的系统中,同时与市面上的脉搏血氧仪通过动物实验进行对比验证.结果 测试数据经线性相关性分析,相关系数都在0.8左右,且得到的表达式的延伸曲线与临床经验定标曲线基本趋势一致.结论 本文采用的拟合方法在提高血氧准确度方面具有一定的研究价值.     

基于ZigBee的血氧饱和度检测技术与模块研制

目的：为了及时、准确、方便、无约束地检测血氧饱和度,本文研制一种无线血氧饱和度检测模块。方法：结合穿戴式检测技术和ZigBee短距离无线通信技术,设计出基于ZigBee的无线血氧饱和度检测模块。该模块由光电容积脉搏波微型化检测模块、ZigBee接入终端及上位机数据分析处理模块组成,其中数据分析处理采用基于形态匹配的特征提取算法对光电容积脉搏波进行最大值的定位。结果：模块实现的功能有光电容积脉搏波显示,血氧饱和度计算,数据无线传输等。实验表明光电容积脉搏波的最大值检测准确率达到98％,而血氧饱和度的计算误差控制在8．8％以内,满足血氧饱和度的检测要求;此外,ZigBee无线传输技术与光源驱动脉冲调节器均有效减少能量的消耗。结论：本模块设计实现病人的移动监护,具有无线化、低功耗、微型化和高性价比等特点。     

一种计算脉搏血氧饱和度的新方法

由于常用的计算脉搏血氧饱和度的方法一般都存在测量数据不能实时更新的缺点,本文基于NJL5501R光反射器搭建了脉搏波信号测量的硬件平台,并根据脉搏波信号测量中所采集的红光和红外光具有高度的线性相关性的特点,提出一种通过建立红光和红外光的线性回归模型来确定血氧饱和度值的方法,并且分析了参与计算的脉搏波采样点数多少对脉搏波血氧特征值的影响。实验结果表明,本文提出的方法能够在保证测量精度的同时实现血氧饱和度数据的快速更新,为人体脉搏血氧饱和度实时、准确地监测提供了一种有效的途径。     

心电同步在脉搏血氧测试中的应用

本文讨论了血氧饱和度测量中的一种新方法；心电信号的Ｒ波来同步脉表示皮信号，更好地从脉搏波信号中提取物征值。更进一步，根据Ｒ波对脉搏波中平均，提高信噪比，利用平均后的脉搏波计算血氧饱和度，经证明可得到更好的结果。     

三波长无创血氧饱和度测量算法及应用

传统的二波长血氧仪需要在医院非常安静的环境下才能正常测量血氧饱和度。然而,患者肢体运动干扰限制了血氧仪的使用范围,尤其是在可穿戴的、走动环境下的使用。本研究提出在探头内除660nm和940nm测量光源外增加810nm光源作为参考信号,根据Beer-Lambert定理建立新的测量算法,在硬件方面采用非线性均衡电路,在软件方面构造自适应滤波器,以便从光电容积脉搏波信号中移除运动干扰信号。实验证明,该方法明显降低了运动干扰,使得测量准确、可靠,在使用可穿戴式设备的移动监护和小儿科监护方面具有广泛的应用前景。     

脉搏血氧饱和度检测中自适应滤波消除运动伪差的方法研究

目的研究脉搏血氧饱和度检测系统中运动伪差的消除方法,以提高脉搏血氧仪检测性能。方法通过脉搏血氧仪中的双光束构造噪声参考信号,利用最小均方自适应滤波法消除运动伪差干扰的影响。结果建立了脉搏血氧饱和度检测中消除运动伪差的计算方法,可成功地从运动伪差中提取正常光电容积脉搏波信号作为计算氧饱和度的依据。结论该计算方法简单,可用于实时处理,且测量结果可靠,为进一步抑制脉搏血氧仪噪声奠定了基础。     

线性回归算法提取脉搏血氧特征值初步验证

目的:准确提取脉搏血氧信号特征值R是计算脉搏血氧饱和度的关键。传统的R值提取算法大多采用脉搏波的峰谷值法,需要多个周期的平均来提高精度,存在移动步长难以确定、实时性差等缺点。本文提出一种动态实时的R值提取算法。方法:基于近红外光谱技术(Near infrared spectroscopy,NIRS)的测量原理,建立了红外光(IR)和红光(RD)两束透射光强信号的线性回归模型,并确定回归系数b与特征值R之间的定量关系。以纯数字医用放大器为实验平台,搭建了光源驱动电路和光电检测电路,采集的光电容积脉搏波(Photoplethysmography,PPG)信号由蓝牙USB接口传输至计算机,然后进行线性相关性分析及提取算法验证。结果:分析发现IR和RD两束透射光强信号之间具有很强的相关性(r>0.9),运用线性回归法提取的特征值R可以准确的反映正常血氧饱和度值以及在主动闭气过程中血氧饱和度的下降过程。结论:初步验证结果表明,线性回归算法可以有效的进行脉搏血氧信号特征值的动态估算。     

对脉搏血氧定量法进行多重散射并研究其效应的一种简单光子衍射分析方法

光子衍射理论可用以获取一个将传输模式和反射模式脉搏血氧定量法测量得到的ac-dc强度比率与动脉氧饱和度(SaO_2)相关联的解析表达式。通过将光子衍射分析的结果与使用基于Beer-Lambert法则且忽略了散射效应的分析方法所获得的数据相比较,可对多重散射的效应进行研究。结果表明,红光和红外光传输路径的平均长度的差异,造成了血氧定量法的定标曲线易于受组织在两个波宽光谱带上的所有衰减因数以及被搏动的动脉血液吸收的影响。因此,定标曲线的形状会受到组织血液容积、源探测头置放的位置以及其它改变了组织衰减因数波长依赖性的变量的影     

反射式血氧饱和度检测系统研制

反射式血氧仪可以有效避免使用范围受限,但反射式脉搏血氧信号十分微弱,容易受噪声干扰使血氧参数的提取难度加大。为获得高质量有效的反射式容积脉搏波,系统设计中提出一种基于集成芯片AFE4490的脉搏血氧信号检测方案,对比几种基于小波变换的滤波算法去噪效果,完成对血氧信号较优的去噪处理。系统样机经调试后,基本实现反射方式对脉搏血氧饱和度的检测功能。     

用自适应AR模型提高血氧饱和度测量中脉搏波信号的检出率

血氧饱和度是人体一项重要的生理参数，它的准确测量对于生理研究及医学应用都具有很重要的意义。对血氧饱和度的无创伤检验通常采用双波长法，在该方法中，血氧饱和度的计算是以识别脉搏波并提取其特征值为基础进行的。由于采用双波长法得到的脉搏波信噪比较低，且脉搏波又不具有明显的特征（例如心电信号中有ＱＲＳ波群），因此常用的脉搏波波形识别方法正确检出率不高，经常出现漏检或误检。本文提出利用时间序列建模的方法，建立     

Evaluation of a new reflectance pulse oximeter for clinical applications

The design of a noninvasive reflectance pulse oximeter that uses the same principle of transmittance pulse oximeter and analyses the oxygen saturation of arterial blood was described. Four sets of red and infra-red LEDs were used as light sources. The respective reflectance photoelectric outputs were used to make an internal calibration curve of the instrument relative to the arterial oxygen saturation values measured with a Co-Oximeter (OSM-3) in five healthy nonsmoking subjects during steady-state hypoxaemia. The accuracy of the present instrument was studied in six patients with respiratory failure. From 22 samples, a good correlation coefficient (0.98) with a standard deviation of 1.42 was obtained in the range between 73 and 100 per cent between the arterial oxygen saturation measured with the present instrument and that with the Co-Oximeter. The result strongly suggests the usefulness of this oximeter in monitoring patients with hypoxaemia.     

Near-infrared transmittance pulse oximetry with laser diodes

Pulse oximeters are widely used for noninvasive monitoring of oxygen saturation in arterial blood hemoglobin. We present a transmittance pulse oximetry system based on near-infrared (NIR) laser diodes (750 and 850 nm) for monitoring oxygen saturation of arterial blood hemoglobin. The pulse oximetry system is made up of the optical sensor, sensor electronics, and processing block. Also, we show experimental results obtained during the development of the whole NIR transmittance pulse oximetry system along with modifications in the sensor configuration, signal processing algorithm, and calibration procedure. Issues concerning wavelength selection and its implications for the improvement of the transmittance pulse oximetry technique are discussed. The results obtained demonstrate the proposed system's usefulness in monitoring a wide range of oxygen saturation levels.     

Noninvasive method for measuring local hemoglobin oxygen saturation in tissue using wide gap second derivative near-infrared spectroscopy

A simple continuous wave near-infrared algorithm for estimating local hemoglobin oxygen saturation in tissue (%StO2) is described using single depth attenuation measurements at 680, 720, 760, and 800 nm. Second derivative spectroscopy was used to reduce light scattering effects, chromophores with constant absorption, baseline/instrumentation drift, and movement artifacts. Unlike previous second derivative methods which focused primarily on measuring deoxyhemoglobin concentration; a wide 40 nm wavelength gap used for calculating second derivative attenuation significantly improved sensitivity to oxyhemoglobin absorption. Scaled second derivative attenuation at 720 nm was correlated to in vitro hemoglobin oxygen saturation to generate a %StO2 calibration curve. The calibration curve was insensitive to total hemoglobin, optical path length, and optical scattering. Measurement error due to normal levels of carboxyhemoglobin, methemoglobin, and water absorption were less than 10 %StO2 units. Severe methemoglobinemia or edema combined with low blood volume could cause StO2 errors to exceed 10 StO2 units. Both a broadband and commercial four-wavelength spectrometer (InSpectra) measured %StO2. The InSpectra tissue spectrometer readily detected limb ischemia on 26 human volunteers for hand, forearm, and leg muscles. A strong linear correlation, r2>0.93, between StO2 and microvascular %SO2 was observed for isolated animal hind limb, kidney, and heart.     

Measurement of oxygen saturation in venous blood by dynamic near infrared spectroscopy

A method for the measurement of oxygen saturation in the venous blood, SvO2, based on optical measurements of light absorption in the infrared region is presented. The method consists of applying relatively low external pressure of 25 mm Hg on the forearm, thereby increasing the venous blood volume in the tissue, and comparing the light absorption before and after the external pressure application. SvO2 has been determined from light absorption measurements in two wavelengths, before and after the pressure application, using a formula derived for two adjacent wavelengths. The method has been applied to the hands and fingers of 17 healthy male subjects, using wavelengths of 767 and 811 nm. SaO2, the oxygen saturation for arterial blood, was also obtained from photoplethysmographic measurements in these two wavelengths (pulse oximetry) using the same formula. The mean (+/- SD) value of SaO2 was 94.5% (+/- 3.0). The mean value of SvO2 was 86.2% (+/- 4.1) for the finger and 80.0% (+/- 8.2) for the hand. These SvO2 values are reasonable for the finger and the hand where arterio-venous anastomoses exist. The method enables the measurement of SvO2 in the limbs, a parameter which is related to tissue blood flow and oxygen consumption.     

The oxygen affinity of sickle hemoglobin

The right-shifted oxyhemoglobin dissociation curve of sickle cell disease (SCD) has been thought to result in abnormally low arterial oxygen saturation (S(o)(2)), even when oxygen partial pressure (P(o)(2)) is normal. However, without polymer formation (minimal under normoxic conditions), HbS oxygen affinity is normal. We hypothesized that in SCD, in vivo S(o)(2) is normal when P(o)(2) is normal. We retrospectively examined 50 blood gas and COoximetry samples from SCD patients and from controls matched for pH, P(o)(2), and carboxyhemoglobin. Control data fell close to the Severinghaus curve, as did non-hypoxemic ( [Formula: see text] ) SCD data. In contrast, hypoxemic (S(o)(2)) < 92.5% SCD data fell well below the standard curve. Thus, although SCD patients' oxygen affinity is low under hypoxic conditions, it is normal at normal arterial S(o)(2). Therefore, a finding of abnormally low saturation demonstrates that P(o)(2) is abnormally low. Given our previous finding that pulse oximetry faithfully reflects saturation in SCD, low pulse oximeter readings in SCD constitute reliable evidence of impaired gas exchange.     

Oxygen saturation determined using a novel wavelet ratio surface

A wavelet-based method is presented for oxygen saturation measurement using photoplethysmogram signals from a standard pulse oximeter device. The transform moduli of both red and infrared signals are used to derive a novel wavelet ratio surface. Projection of the pulse component onto this surface allows optimal derivation of oxygen saturation.     

Trans-abdominal monitoring of fetal arterial blood oxygenation using pulse oximetry

Pulse oximetry (oxygen saturation monitoring) has markedly improved medical care in many fields, including anesthesiology, intensive care, and newborn intensive care. In obstetrics, fetal heart rate monitoring remains the standard for intrapartum assessment of fetal well being. Fetal oxygen saturation monitoring is a new technique currently under development. It is potentially superior to electronic fetal heart rate monitoring (cardiotocography) because it allows direct assessment of both the fetal oxygen status and fetal tissue perfusion. Here we present the analysis for determining the most optimal wavelength selection for pulse oximetry. The wavelengths we chose as the most optimal are the first in the range of 670-720 nm and the second in the range of 825-925 nm. Further, we discuss the possible systematic errors during our measurements and their contribution to the obtained saturation results. We present feasibility studies for fetal pulse oximetry, monitored noninvasively through the maternal abdomen. Our preliminary experiments show that the fetal pulse can be discriminated from the maternal pulse and thus, in principle, the fetal arterial oxygen saturation can be obtained. We present the methodology for obtaining these data, and discuss the dependence of our measurements on the fetal position with respect to the optode assembly.     

Pulse oximetry in the pulmonary tissue for the non-invasive measurement of mixed venous oxygen saturation

The oxygen saturation of the systemic arterial blood is associated with the adequacy of respiration, and can be measured non-invasively by pulse oximetry in the systemic tissue. The oxygen saturation of the blood in the pulmonary artery, the mixed venous blood, reflects the balance between oxygen supply to the systemic tissues and their oxygen demand. The mixed venous oxygen saturation has also clinical significance because it is used in Fick equation for the quantitative measurement of cardiac output. At present the measurement of the mixed venous oxygen saturation is invasive and requires insertion of a Swan-Ganz catheter into the pulmonary artery. We suggest a noninvasive method for the measurement of the mixed venous oxygen saturation in infants, pulmonary pulse oximetry. The method is similar to the systemic pulse oximetry, which is based on the different light absorption curves of oxygenated and deoxygenated hemoglobin and on the analysis of photoplethysmographic curves in two wavelengths.