Niklas M, Moser U, Buehrer A, Valentin R, Abicht J, Baschnegger H, Christ F
Institut für Anaesthesiologie, Ludwig Maximillians University Munich, Klinikum Grosshadern, Marchioninistr. 15, D-82362 Munich, Germany.
Eur J Med Res. 1998 May 12;3(5):241-8.
Photoplethysmography enables non-invasive investigation of the volume pulse in the microvasculature of patients. We previously have shown that time-discrete analysis enables identification of highly reproducible characteristics of the volume pulse in absolute values. The method would be of particular interest, if the perfusion of deeper tissue layers like the skeletal muscle can be assessed. The aim of the current study was to investigate the attenuation of the photoplethysmographic signal by different tissues and up to which depth of tissue a time-discrete analysis of the photoplethysmographic signal would be possible. For the recordings we used the time-discrete near-infra-red photoplethysmography (NIRP), a reflection photoplethysmograph measuring at wavelengths of 840 nm and 640 nm. In an in vitro circuit filled with bovine blood we generated a typical and exactly reproducible volume pulse. On a platform the NIRP sensor probe was placed above the artificial vessel and recordings of the volume pulse were obtained by varying the sensor-vessel-distance with increasing layers of water, blood-agar or bovine skeletal muscle tissue. - The amplitude of the NIR signal was attenuated to 50% by each layer of 2.01 mm of water, 1.42 mm of blood-agar and 1.05 mm of bovine skeletal muscle tissue. A time-discrete analysis could be performed up to a depth of 15 mm of water, 6 mm of blood-agar and 5 mm of bovine skeletal muscle tissue. - As the photoplethysmographic curve is strongly attenuated even by a few millimetres of water we suggest that the NIRP signal mirrors the perfusion of the superficial tissue layer and mainly originates from the subpapillary capacious plexus. - We conclude that with the equipment used in this study volume pulsations in deeper layers of tissue like skeletal musculature can not be assessed.
光电容积脉搏波描记术能够对患者微血管系统中的容积脉搏进行无创检测。我们之前已经表明，时间离散分析能够以绝对值识别容积脉搏的高度可重复特征。如果能够评估像骨骼肌这样更深组织层的灌注情况，该方法将特别有意义。本研究的目的是调查不同组织对光电容积脉搏波信号的衰减情况，以及光电容积脉搏波信号的时间离散分析在组织多深的深度范围内是可行的。对于记录，我们使用了时间离散近红外光电容积脉搏波描记术（NIRP），这是一种在840 nm和640 nm波长下进行测量的反射式光电容积脉搏波描记仪。在一个充满牛血的体外循环装置中，我们产生了一个典型且完全可重复的容积脉搏。在一个平台上，将NIRP传感器探头放置在人造血管上方，通过增加水、血琼脂或牛骨骼肌组织层来改变传感器与血管的距离，从而获得容积脉搏的记录。 - 近红外信号的幅度被每层2.01 mm的水、1.42 mm的血琼脂和1.05 mm的牛骨骼肌组织衰减至50%。时间离散分析可以在15 mm深的水、6 mm深的血琼脂和5 mm深的牛骨骼肌组织范围内进行。 - 由于即使几毫米厚的水也会使光电容积脉搏波曲线强烈衰减，我们认为NIRP信号反映了浅表组织层的灌注情况，并且主要源自乳头下宽大的静脉丛。 - 我们得出结论，使用本研究中所使用的设备，无法评估像骨骼肌这样更深组织层中的容积搏动情况。
