无线传输在脉搏血氧饱和度无创监测中的应用

随着光电子技术的快速发展,基于光电检测原理的血氧饱和度在线测量方法得到了广泛研究。本文对传统双波长透射式血氧饱和度测量方法进行了改进,并在系统中应用了无线数字信号传输和数据小波处理方法。经实验验证,基于以上原理提出的脉搏血氧饱和度检测方法和无线数字信号传输方法,有效地消除了非血氧成分与其他干扰因素对测量结果的影响,并且突破了测量的空间限制。     

自适应脉搏氧系统设计与实现

介绍一种自适应脉搏氧测量系统,使用模拟开关切换反馈电阻阻值,粗调系统增益;通过前级反馈调节MCU的DA输出,改变恒流驱动大小,微调系统增益。在两种机制协调下,实现系统增益精确控制,实现信号的宽范围测量,满足在低灌注指数下对弱脉搏的信号采集,并实现脉率、灌注指数、血氧饱和度的精确计算。     

Photoplethysmographic measurements from the esophagus using a new fiber-optic reflectance sensor

A prototype fiber-optic reflectance-mode pulse oximetry sensor and measurement system is developed for the purposes of estimating arterial oxygen saturation in the esophagus. A dedicated probe containing miniature right-angled glass prisms coupled to light sources and a photodetector by means of optical fibers is designed and used to record photoplethysmographic (PPG) signals from the esophageal epithelium in anesthetized patients. The probe is inserted simply by an anesthesiologist in all cases, and signals are recorded successfully in all but one of 20 subjects, demonstrating that esophageal PPG signals can be reliably obtained. The mean value of the oxygen saturation recorded from the esophagus for all subjects is 94.0 ± 4.0%. These results demonstrate that SpO(2) may be estimated in the esophagus using a fiber-optic probe.     

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.     

Computer analysis system of blood oxygen saturation in an animal hypoxia model

An experimental animal hypoxia model has been developed. It consists of two sensors (an in vitro and in vivo model), an experimental device and a computer signal processing system. This method can easily be applied to determine and analyse blood oxygen saturation at various hypoxia levels. It can also be used to evaluate the accuracy of pulse oximetry over a wide range of oxyhemoglobin desaturation levels. The DC and AC components of recorded red and infra-red signals, the dual-wavelength ratio R₁₂ and the reading of a pulse oximeter (SpO₂) can be automatically calculated and displayed on a computer screen. Preliminary results of the animal hypoxia test indicate that the measurements made by the instrument correlate well with the oxygen saturation readings of the automatic blood gas analyser AVL945. The computer analysis system is suitable for repeated estimations in the animal model.     

Investigation of photoplethysmographic signals and blood oxygen saturation values on healthy volunteers during cuff-induced hypoperfusion using a multimode PPG/SpO2 sensor

Photoplethysmography (PPG) is a technique widely used to monitor volumetric blood changes induced by cardiac pulsations. Pulse oximetry uses the technique of PPG to estimate arterial oxygen saturation values (SpO?). In poorly perfused tissues, SpO? readings may be compromised due to the poor quality of the PPG signals. A multimode finger PPG probe that operates simultaneously in reflectance, transmittance and a combined mode called "transreflectance" was developed, in an effort to improve the quality of the PPG signals in states of hypoperfusion. Experiments on 20 volunteers were conducted to evaluate the performance of the multimode PPG sensor and compare the results with a commercial transmittance pulse oximeter. A brachial blood pressure cuff was used to induce artificial hypoperfusion. Results showed that the amplitude of the transreflectance AC PPG signals were significantly different (p < 0.05) than the AC PPG signals obtained from the other two conventional PPG sensors (reflectance and transmittance). At induced brachial pressures between 90 and 135 mmHg, the reflectance finger pulse oximeter failed 25 times (failure rate 42.2 %) to estimate SpO? values, whereas the transmittance pulse oximeter failed 8 times (failure rate 15.5 %). The transreflectance pulse oximeter failed only 3 times (failure rate 6.8 %) and the commercial pulse oximeter failed 17 times (failure rate 29.4 %).     

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.     

Neural network for photoplethysmographic respiratory rate monitoring

The reflection mode photoplethysmographic (PPG) signal was studied with the aim of determining respiratory rate. The PPG signal includes respiratory synchronous components, seen as frequency modulation of the heart rate (respiratory sinus arrhythmia), amplitude modulation of the cardiac pulse and respiratory-induced intensity variations (RIIVs) in the PPG baseline. PPG signals were recorded from the foreheads of 15 healthy subjects. From these signals, the systolic wavefrm diastolic waveform, respiratory sinus arrhythmia, pulse amplitude and RIIVs were extracted. Using basic algorithms, the rates of false positive and false negative detection of breaths were calculated separately for each of the five components. Furthermore, a neural network was assessed in a combined pattern recognition approach. The error rates (sum of false positive and false negative breath detections) for the basic algorithms ranged from 9.7% (pulse amplitude) to 14.5% (systolic waveform). The corresponding values for the neural network analysis were 9.5–9.6%. These results suggest the use of a combined PPG system for simultaneous monitoring of respiratory rate and arterial oxygen saturation (pulse oximetry).     

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.     

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.     

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。     

无损伤血氧饱和度测量的研究

本文介绍无损伤血氧饱和度测量的原理和实用算法,以及脉搏式血氧饱和度仪的设计。     

基于安卓和蓝牙通信的智能生理监护仪的设计

目的为满足生理监测设备多功能、便携式、网络化的发展需求,本文将生理监测技术和无线通信技术相结合,设计了一款便携式的智能生理监护仪,将多种生理参数的检测通过蓝牙传输到手机,使被监测者行动不受拘束,实时、可移动地获取和传输人体生理参数,满足家庭监护和远程医疗的需求。方法该监测仪主要由MSP430f6638作为主控芯片,包括脉搏波采集电路与心电信号采集电路,单片机分时采集两路信号,进行中值滤波与均值滤波后将信号通过串口通信传输给蓝牙模块,通过蓝牙模块与手机自带的蓝牙进行通信。结果该监护仪包含少量外围电路,只需连接3个心电极与1个血氧探头,加之简单的手机应用操作。通过蓝牙传输,可以通过手机实时显示心率、血氧饱和度、血压等生理参数。结论该生理监护仪结构简单,经济实惠,操作方便,实时监测,提供了一个便携、高效、实时的家居化健康服务平台。     

In vitro measurements of absolute blood oxygen saturation using pulsed near-infrared photoacoustic spectroscopy: accuracy and resolution

Pulsed photoacoustic spectroscopy was used to measure blood oxygen saturation in vitro. An optical parametric oscillator laser system provided nanosecond excitation pulses over the wavelength range 740-1040 nm which were used to generate photoacoustic signals in a cuvette through which a saline suspension of red blood cells was circulated. The signal amplitude and the effective attenuation coefficient were extracted from the photoacoustic signals as a function of wavelength to provide photoacoustic spectra of the blood. From these, the relative concentrations of oxy- and deoxyhaemoglobin, and therefore blood oxygen saturation (SO2), were determined using forward models of the absorbed energy distribution based on diffusion theory. A standard linear model of the dependence of absorbance on the concentration of chromophores was also used to calculate the blood oxygen saturation from the signal amplitude spectra. The diffusion approximation model was shown to produce the highest accuracy in blood SO2. The photoacoustically determined oxygen saturation was found to have an accuracy of +/-4% SO2 for signal amplitude data and +/-2.5% SO2 for effective attenuation spectra. The smallest change in oxygen saturation that can be measured using this technique was +/-1% SO2.     

食道内脉搏氧饱和度信号来源及其影响因素

研究食道内脉搏氧饱和度(SeO2)信号的来源及其影响因素。在成年杂交犬降主动脉(DA)水平记录屏蔽DA和中断食管血供前后的SeO2,且记录传感器与食管壁不同接触压力下及机械通气前后在食管内不同深度和方向的SeO2,同期舌氧饱和度(StO2)作为对照。屏蔽DA后SeO2信号消失(P<0.001),中断食管血供前后的SeO2无统计学差异(P>0.05),放置于食管内不同深度和方向的传感器在机械通气前后以及与食管壁不同接触压力下,所获SeO2读数有显著差异(P<0.05)。SeO2信号主要来源其相邻大血管。机械通气,传感器的位置及其与食管壁接触压力均可影响SeO2信号。     

Instillation of normal saline before suctioning in patients with pneumonia

This study was conducted to investigate the effects of a no saline, a 2 ml and a 5 ml saline instillation prior to endotracheal suctioning on oxygen saturation in patients with pneumonia. The subjects in this study were 16 pneumonic patients with a tracheotomy tube, who had been admitted to the neuro-surgical intensive care unit at a university hospital in Seoul Korea. All three (0, 2 and 5 ml) saline instillation methods were applied to the 16 patients. The methods were randomly assigned to each patient. Each of the instillation methods was applied in a four-step sequence: 1) recording the level of oxygen saturation (baseline levels), 2) instilling normal saline, 3) supplying oxygen and suctioning, and 4) recording the level of oxygen saturation. The oxygen saturation was evaluated using pulse oximetry. The recovery times for oxygen saturation to return to baseline levels following suctioning were, just after suctioning, 45 seconds after suctioning and in excess of 5 minutes with 0, 2 and 5 ml saline instillations, respectively. Instillation of normal saline before suctioning could have an adverse effect on oxygen saturation, and should be used carefully as a routine intervention in patients who have pneumonia.     

基于三波长肝储备功能检测仪的血氧饱和度算法研究

研究基于三波长的血氧饱和度计算算法。以自主研发的三波长(660 nm,805 nm,940 nm)肝储备功能检测仪为实验仪器,运用改进后的脉搏分光光度法原理,采取阈值法提取出脉搏波的交直流量,最后用不同的算法计算人体的血氧饱和度并作出比较。通过实验证明,使用拟合定标曲线得出的公式计算血氧饱和度,其结果好于使用理论推导出的公式计算出的结果。采取拟合定标曲线的方法取得了较好的效果,具有一定的临床实用性。     

Cardiorespiratory functioning of preterm infants: Stability and risk associations for measures of heart rate variability and oxygen saturation

Cardiorespiratory measures are used with increasing frequency to assess individual differences in development in full-term and preterm infants, yet little information exists concerning the stability of these measures or their relations to each other. This study assessed three common cardiac measures (heart period, heart period variability, and vagal tone) and two measures of arterial oxygenation based on pulse oximetry (mean pulse oxygen saturation and variability) in a sample of 35 preterm infants. Data were collected on five occasions: on 3 consecutive days in the early neonatal period, at 34 weeks postconceptional age, and at discharge. Results indicate both short-term and longer term stability for all cardiac measures. Oxygen saturation demonstrated only short-term stability prior to 34 weeks. Mean heart period was positively associated with both measures of heart period variability at each assessment point, while mean oxygen saturation level was inversely related to oxygen saturation variability. In addition, significant associations between cardiorespiratory patterns and perinatal risk measures were found. It is concluded that these measures reflect stable characteristics of neuroregulatory function in preterm infants.© 1994 John Wiley & Sons, Inc.