Christ F, Athelogou M, Niklas M, Baschnegger H, Moser C M, Peter K, Messmer K
Institute of Anaesthesiology, Ludwig Maximilians Universität München, Marchioninistr. 15, Munich D-81377, Germany.
Eur J Med Res. 1996 Feb 22;1(5):237-43.
In pulse oximetry the principles of photoplethysmography are used for determination of heart rate and in some devices to also display the volume pulse. It has been suggested, that a more detailed analysis of the signal may allow quantitative analysis of peripheral hemodynamic events. We describe a new computer assisted time discrete analysis of the volume pulse, studying its reliability and the method s fundamental assumption of a linear relationship between changes in amplitude and changes in time sequences of the volume pulse.
In a finger clip two diodes emit near infrared (840 nm, NIR) and red light (640nm, RED) into the finger tip, where it is remitted mainly by the erythrocytes. 70 sec of recorded signal is filtered and the resulting volume pulse analysed off-line using a computer. On each volume pulse the time of the first (Tmax), the second maximum (time of dicrote, Td) and the duration of the volume pulse (Tp) are measured and the mean values displayed. In addition, the fundamental arterial oscillation Tag = Td - Tmax and all the above values in relation to Tp are calculated. Using NIRP, 54 healthy young volunteers (19 female, mean age 27.0 +/- 3.4 years) were studied and the individual mean values calculated from 960 measurements. The reliability during 10 repetitive measurements was investigated in 26 of the 54 volunteers. In 12 subjects 5 repetitive measurements were obtained from each finger and compared with each other. In 11 subjects the linear relationship between amplitude and time sequence was tested on > 30 000 single volume pulses. The finger clip photoelectrode was levelled with the right atrium in all measurements, skin close to the clip and room temperature were recorded.
From the mean individual values the following time discrete values were calculated for the NIR signal (n = 41): Tp = 882.3 +/- 142.6 ms, Tmax = 214.8 +/- 28.3 ms, Td = 452.7 +/- 32.4 ms, Tdec = 667.4 +/- 133.6 ms, Tag = 237.9 +/- 36.3 ms, Tmax/Tdec = 0.34 +/- 0. 07, Td/Tdec = 0.7 +/- 0.11. For each parameter the individual standard deviation during 10 repetitive measurements (26 subjects) ranged between 2.2 and 6.1%. The time sequences found were not significantly different between the individual fingers. A linear relationship between changes in time sequence and changes in amplitude was found in all tested subjects (mean r = 0.96).
These results show, that the values obtained with time discrete NIRP are highly reproducible and show an individual SD of less than 6.5% under steady state conditions. The linear relationship between time sequence and amplitude found in the present study has to be confirmed in further studies on patients with pathologies of the macro- and microcirculation.
在脉搏血氧测定法中，光电容积描记法的原理用于测定心率，在一些设备中还用于显示容积脉搏。有人提出，对信号进行更详细的分析可能有助于对外周血流动力学事件进行定量分析。我们描述了一种新的计算机辅助的容积脉搏时间离散分析方法，研究其可靠性以及该方法关于容积脉搏幅度变化与时间序列变化之间线性关系的基本假设。
在一个指夹中，两个二极管向指尖发射近红外光（840nm，NIR）和红光（640nm，RED），光在指尖主要由红细胞反射。记录70秒的信号，经过滤波后，使用计算机对得到的容积脉搏进行离线分析。在每个容积脉搏上，测量第一个最大值的时间（Tmax）、第二个最大值的时间（重搏波时间，Td）和容积脉搏的持续时间（Tp），并显示平均值。此外，计算基本动脉振荡Tag = Td - Tmax以及上述所有值与Tp的关系。使用近红外容积脉搏波（NIRP），对54名健康年轻志愿者（19名女性，平均年龄27.0±3.4岁）进行研究，并从960次测量中计算个体平均值。在54名志愿者中的26名中研究了10次重复测量期间的可靠性。在12名受试者中，从每个手指获得5次重复测量并相互比较。在11名受试者中，在超过30000个单个容积脉搏上测试了幅度与时间序列之间的线性关系。在所有测量中，指夹光电极与右心房齐平，记录靠近指夹的皮肤温度和室温。
根据个体平均值，计算出近红外信号（n = 41）的以下时间离散值：Tp = 882.3±142.6毫秒，Tmax = 214.8±28.3毫秒，Td = 452.7±32.4毫秒，Tdec = 66
