BT-700 Operator Manual 20
P/N : 700-ENG-OPM-EUR-R02
Bistos Co.,Ltd.
2018,03
Section
5
Operation
5.1
Electromagnetic Interference
Certain strong electromagnetic fields can interfere with the SpO2 sensor and
cause a false SpO2, Pulse rate and temperature reading that does not originate
from the patient. This interference is rare, and usually found in the vicinity of
large machinery. In order to avoid the possibility of these interfering signals
being misinterpreted, the following procedure should be followed whenever the
monitor is to be used in a new location, or if it is known that electrical machinery
is being operated in the vicinity.
After connecting the SpO2 sensor, turn on the monitor and observe the pulse rate
indications on the screen for 30 seconds. Intermittent display of random heart
rates is acceptable. However, if there is a constant display of a physiological
pulse rate lasting more than 5 seconds, this is an indication that there is a source
of electromagnetic interference in the vicinity. The following steps should be
taken to determine if it is possible to use the monitor in this environment.
Move all line cords and line-powered equipment at least 6 feet away from
the BT-700. Check for extension cords running behind or under the bed and
equipment in adjacent rooms. If the artifact pulse rate indication ceases, the
monitor may be used normally.
Remove the line cord from the monitor’s power supply. If the artifact pulse
rate indication ceases, the monitor may be used normally.
If these measures do not result in cessation of the pulse rate artifact, the monitor
cannot be safely used in this environment.
5.2
Basic operation
The BT-700 uses pulse oximetry to measure functional oxygen saturation in the blood.
Pulse oximetry works by applying a sensor to a pulsating arteriolar vascular bed, such
as a finger or toe. The sensor contains a dual light source and a photo detector. 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 (SpO2). Because a measurement of SpO2 is dependent
upon light from the sensor, excessive ambient light can interfere with this
measurement. Specific information about ambient conditions, sensor application, and
patient conditions is contained throughout this manual. Pulse oximetry is based on
two principles: that oxyhemoglobin and deoxyhemoglobin differ in their absorption of
red and infrared light (spectrophotometry), and that the volume of arterial blood in
tissue (and hence, light absorption by that blood) changes during the pulse
(plethysmography). A pulse oximeter determines SpO2 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
oximetry sensor serve as light sources; a photo diode serves as the photo detector.
