13 - 3
◆ Hemoglobinopathies and synthesis disorders such as thalassemias, Hb s, Hb c, sickle cell, etc.
◆ Hypocapnic or hypercapnic conditions
◆ Birthmark(s), tattoos, skin discolorations, moisture on skin, deformed or abnormal fingers. etc.
■ Interfering substances:
◆ Intravascular dyes (such as indocyanine green, methylene blue, indigo carmine, etc.)
◆ Dyes in the measure site, such as nail polish.
■ Environmental conditions:
◆ Excessive ambient light
◆ Electrosurgery equipment
◆ Defibrillation (may cause inaccurate reading for a short amount of time)
◆ Excessive patient/sensor motion
◆ Electromagnetic field
◆ Arterial catheters and intra-aortic balloon
■ Others
◆ Inappropriate positioning of the SpO
2
sensor, or use of incorrect SpO
2
sensor
◆ Cuff or arterial blood pressure measurement device on the same limb as the SpO
2
sensor.
13.4 SpO
2
Display
• PI is only available for Mindray SpO
2
and Masimo SpO
2
.
(1) Pleth waveform (Pleth): visual indication of patient’s pulse. The waveform is not normalized.
(2) Oxygen saturation of arterial blood (SpO
2
): percentage of oxygenated hemoglobin in relation to the sum of
oxyhemoglobin and deoxyhemoglobin.
(3) Perfusion indicator: the pulsatile portion of the measured signal caused by arterial pulsation.
(4) Pulse rate (derived from the pleth wave): detected pulsations per minute.
(5) Perfusion index (PI): gives the numerical value for the pulsatile portion of the measured signal caused by arterial
pulsation. PI is an indicator of the pulsatile strength. You can also use it to assess the SpO
2
signal strength.
For Mindray SpO
2
module,
◆ Above 1 is optimal.
◆ Between 0.3 and 1 is acceptable.
◆ Below 0.3 indicates low perfusion. Reposition the SpO
2
sensor or find a better site. If low perfusion persists,
choose another method to measure oxygen saturation if possible.
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