Department of Medical Informatics, Kitasato University, Sagamihara, Kanagawa, Japan.
J Clin Monit Comput. 2010 Feb;24(1):35-9. doi: 10.1007/s10877-009-9206-8.
Serious accidents during hemodialysis such as a large amount of blood loss are often caused by venous needle dislodgement. To develop a bleeding sensor based on a photo sensor for monitoring the needle sites, we studied effects of liquids and porcine blood on light transmission through a thin gauze pad with a basic photo sensor.
The photo sensor consisted of an ordinary electrical circuit, a light emitting diode (LED, lambda max = 645 nm), a photo diode (PD), and a thin gauze pad placed between the LED and PD that were tightly attached to the edges of a plastic clip. The light transmitted through the gauze pad, soaked with liquids or porcine blood dropped on it, was measured with a digital voltmeter. The liquids were reverse osmosis water, physiological saline, glucose in water at 5, 10, 20, 40 and 50%, porcine plasma, and porcine blood (Hct 40, 30 and 20%).
The liquids on a tight-weave gauze pad, significantly increased the voltage (light transmission) from 0.412 +/- 0.003 V (SD) to 0.794 +/- 0.025 V (minimum, by reverse osmosis water) and to 0.945 +/- 0.011 V (maximum, by 50% glucose). The porcine blood significantly decreased the voltage from 0.412 to 0.195 +/- 0.030 V in Hct 40%, to 0.334 +/- 0.035 in Hct 30%, to 0.397 +/- 0.007 V in Hct 20%. The higher the concentration of glucose, the more the light transmission increased. The higher concentration of Hct, the more the light transmission decreased. Similar results were also shown for the loose-weave pad.
Using two types of gauze pads, we confirmed that liquids significantly increased light transmission through gauze pad, but porcine blood decreased light transmission. This opposite response can be used to distinguish liquids from blood on a gauze pad.
血液透析过程中严重的事故，如大量失血，往往是由于静脉针脱落引起的。为了开发一种基于光电传感器的出血传感器来监测针头部位，我们研究了液体和猪血对通过带有基本光电传感器的薄纱布垫的光传输的影响。
光电传感器由普通电路、发光二极管（LED，λmax=645nm）、光电二极管（PD）和置于 LED 和 PD 之间的薄纱布垫组成，这些传感器被紧紧地固定在塑料夹的边缘上。通过数字电压表测量纱布垫上的液体或猪血滴浸湿后的光传输。液体为反渗透水、生理盐水、浓度为 5%、10%、20%、40%和 50%的葡萄糖、猪血浆和猪血（Hct 为 40%、30%和 20%）。
在紧密编织的纱布垫上，液体显著增加了电压（光传输），从 0.412±0.003V（SD）到 0.794±0.025V（最小值，反渗透水）和 0.945±0.011V（最大值，50%葡萄糖）。猪血显著降低了电压，从 Hct 40%时的 0.412 降至 0.195±0.030V，Hct 30%时降至 0.334±0.035V，Hct 20%时降至 0.397±0.007V。葡萄糖浓度越高，光传输增加越多。Hct 浓度越高，光传输减少越多。对于疏松编织的垫也得到了类似的结果。
使用两种类型的纱布垫，我们证实液体显著增加了纱布垫的光传输，但猪血降低了光传输。这种相反的反应可以用来区分纱布垫上的液体和血液。
