Справочник Пользователя для Innokas Yhtyma Oy VC150

9-14

VC150 Vital Signs Monitor

KO00065K

: Compatible Nellcor accessories

All approved and VC150 compliant accessories are listed in the VC150 supplies 
and accessories document. Use only accessories listed in that document. If you 
already have an accessory that you want to use with the VC150 monitor, check 
whether it is listed in that document. If it not listed, do not use it with the VC150 
monitor.

The Nellcor SpO

2

 uses pulse oximetry to measure functional oxygen saturation 

in the blood. Pulse oximetry works by applying a Nellcor™ sensor to a pulsating 
arteriolar vascular bed, such as a finger or toe. The sensor contains a dual light 
source and a photodetector. Bone, tissue, pigmentation, and venous vessels 
normally absorb a constant amount of light over time. The arteriolar bed 
normally pulsates and absorbs variable amounts of light during the pulsations. 
The ratio of light absorbed is translated into a measurement of functional 
oxygen saturation (SpO

2

).

Ambient conditions, sensor application, and patient conditions can influence the 
ability of the monitoring system to accurately measure SpO

2

. Pulse oximetry is 

based on two principles: oxyhemoglobin and deoxyhemoglobin differ in their 
absorption of red and infrared light (measured using spectrophotometry), and 
the volume of arterial blood in tissue (and hence, light absorption by that blood) 
changes during the pulse (registered using plethysmography).

A monitoring system determines SpO

2

 by passing red and infrared light into an 

arteriolar bed and measuring changes in light absorption during the pulsatile 
cycle. Red and infrared low-voltage light-emitting diodes (LED) in the sensor 
serve as light sources; a photo diode serves as the photo detector.

Since oxyhemoglobin and deoxyhemoglobin differ in light absorption, the 
amount of red and infrared light absorbed by blood is related to hemoglobin 
oxygen saturation.

The monitoring system uses the pulsatile nature of arterial flow to identify the 
oxygen saturation of arterial hemoglobin. During systole, a new pulse of arterial 
blood enters the vascular bed, and blood volume and light absorption increase. 
During diastole, blood volume and light absorption reach their lowest point. The 
monitoring system bases its SpO

2

 measurements on the difference between 

maximum and minimum absorption (measurements at systole and diastole). By 
doing so, it focuses on light absorption by pulsatile arterial blood, eliminating the 
effects of nonpulsatile absorbers such as tissue, bone, and venous blood.

This signal is processed by the pulse oximeter to determine patient SpO

2

 and 

pulse rate data, which are displayed on the monitor user interface, system 
status, and alarm information. These data are stored on the monitor and 
available for subsequent export.