Vital Signs Monitor User Manual Monitoring SpO
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NOTE:
1 Injected dyes such as methylene blue or intravascular dyshemoglobins such as
methemoglobin and carboxyhemoglobin may lead to inaccurate measurements.
2 Inspect the sensor to ensure that the light emitter and receiver are aligned with each
other and there is no gap between the sensor and the finger. All the light emitted by
the light emitter must pass through the patient's tissue. The sensor cable should be
placed on the back of the hand.
3 Clean and remove any substances such as nail polish from the application site.
Periodically check to ensure that the sensor remains properly positioned on the
patient.
11.4 Measurement Limitations
Certain patient conditions can affect the measurements or cause the loss of the pulse signal.
Inaccurate measurements can be caused but not limited by:
• incorrect sensor application
• high levels of ambient light sources, such as surgical lights (especially those with a xenon
light source), bilirubin lamps, fluorescent lights, infrared heating lamps, and direct sunlight
• failure to cover the sensor with opaque material in high levels of ambient light conditions
• dysfunctional hemoglobins
• low peripheral perfusion
• excessive or violent patient movement
• venous pulsations
• intravascular dyes, such as indocyanine green or methylene blue
• externally applied coloring agents (nail polish, dye, pigmented cream)
• defibrillation
• placement of the sensor on an extremity with a blood pressure cuff, arterial catheter, or
intravascular line
• electromagnetic interference
Loss of pulse signal can occur for the following reasons:
• the sensor is applied too tightly
• a blood pressure cuff is inflated on the same extremity as the one with the sensor attached
• there is arterial occlusion proximal to the sensor
• low peripheral perfusion
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