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4-4 Radical-7 Color Display Signal Extraction Pulse Oximeter Operator’s Manual Radical-7 Color Display Signal Extraction Pulse Oximeter Operator’s Manual 4-54-5

operation

be compromised, and a Low Signal IQ message is displayed in the message area on the

Radical-7 Pulse CO-Oximeter display. When the Low Signal IQ message appears proceed

with caution and do the following:

■ Assess the patient.

■ Check the sensor and ensure proper sensor application. The sensor must be well

secured to the site for the Radical-7 Pulse CO-Oximeter to maintain accurate read-

ings. Also, misalignment of the sensor’s emitter and detector can result in smaller

signals.

■ Determine if an extreme change in the patient’s physiology and blood flow at the

monitoring site occurred, (e.g. an inflated blood pressure cuff, a squeezing motion,

sampling of an arterial blood specimen from the hand containing the pulse oximetry

sensor, severe hypotension, peripheral vasoconstriction in response to hypothermia,

medications, or a spell of Raynaud’s syndrome.)

■ With neonates or infants, check that the peripheral blood flow to the sensor site is not

interrupted. Interruption, for example, may occur while lifting or crossing their legs,

during a diaper change.

After performing the above, if the Low Signal IQ message is displayed frequently or contin-

uously obtaining an arterial blood specimen for CO-Oximetry analysis may be considered

to verify the oxygen saturation value.

LOW PERFUSION

The Radical-7 Pulse CO-Oximeter displays a “Low Perfusion” message when there are

very low amplitude arterial pulsations.

It has been suggested that at extremely low perfusion levels, pulse oximeters can measure

peripheral saturation, which may differ from central arterial saturation

. This “localized

hypoxemia” may result from the metabolic demands of other tissues extracting oxygen

proximal to the monitoring site under conditions of sustained peripheral hypoperfusion.

(This may occur even with a pulse rate that correlates with the ECG heart rate.)

CAUTION: IF THE LOW PERFUSION MESSAGE IS FREQUENTLY DISPLAYED, FIND

A BETTER-PERFUSED MONITORING SITE. IN THE INTERIM, ASSESS

THE PATIENT AND, IF INDICATED, VERIFY OXYGENATION STATUS

THROUGH OTHER MEANS.

Severinghaus JW, Spellman MJ. Pulse Oximeter Failure Thresholds in Hypotension

and Vasoconstriction. Anesthesiology 1990; 73:532-537

ACTIONS TO BE TAKEN

If the SpO

readings show significant differences, do the following:

■ Make sure the emitter and photodetector are aligned directly opposite each other.

■ Select a site where the distance between the emitter and photodetector is mini-

mized.

■ Wipe the sensor site with a 70% isopropyl alcohol pad or rubefacient cream (10-

30% methyl salicylate and 2-10% menthol) for 20-30 seconds to increase perfusion.

However, strong vasodilator creams, such as nitroglycerin paste, are not recom-

mended.

■ If possible, remove electrical noise sources such as electrosurgical units or other

NUMERIC DISPLAY - SpCO

A stable SpCO reading is associated with correct sensor placement, small physiological

changes during the measurement and acceptable levels of arterial perfusion in the patient’s

fingertip (measurement site). Physiological changes at the measurement site are mainly

caused by fluctuations in the oxygen saturation, blood concentration and perfusion.

Inaccurate measurements may be caused by:

■ Significant levels of methemoglobin.

■ Intravascular dyes such as indocyanine green or methylene blue.

■ Abnormal hemoglobin levels.

■ Abnormally low arterial perfusion.

NUMERIC DISPLAY - SpMet

A stable SpMet reading is associated with correct sensor placement, small physiological

changes during the measurement and acceptable levels of arterial perfusion in the patient’s

fingertip (measurement site). Physiological changes at the measurement site are mainly

caused by fluctuations in the oxygen saturation, blood concentration and perfusion.

Inaccurate measurements may be caused by:

■ Intravascular dyes such as indocyanine green or methylene blue.

■ Abnormal arterial perfusion

NUMERIC DISPLAY - PI

The Perfusion Index (PI) display provides a relative numeric indication of the pulse strength

at the monitoring site. It is a calculated percentage between the pulsatile signal and non-

pulsatile signal of arterial blood moving through the site. PI may be used to find the best

perfused site and to monitor physiological changes in the patient. It displays an operating

range of 0.02 percent to 20.00 percent. A percentage greater than 1.00 percent is desired.

Extreme changes in the display number are due to changes in physiology and blood flow.

SIGNAL IQ

The Radical-7 Pulse CO-Oximeter display provides a visual indicator of the plethysmogram

signal quality and an alert when the displayed SpO

values are not based on adequate

signal quality. The signal quality indicator displayed on the Radical-7 Pulse CO-Oximeter

is called the Signal IQ. The Signal IQ can be used to identify the occurrence of a patient’s

pulse and the associated signal quality of the measurement.

With motion, the plethysmographic waveform is often distorted and may be obscured by

artifact. The Signal IQ, shown as a vertical line, coincides with the peak of an arterial pul-

sation. Even with a plethysmographic waveform obscured by artifact, the Radical-7 Pulse

CO-Oximeter locates the arterial pulsation. The pulse tone (when enabled) coincides with

the vertical line of the Signal IQ.

The height of the vertical line of the Signal IQ indicates the quality of the measured signal.

A high vertical bar indicates that the SpO

measurement is based on a good quality signal.

A small vertical bar indicates that the SpO

measurement is based on data with low signal

quality. When the signal quality is very low the accuracy of the SpO

measurement may

operation

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