Page 292 - Clinical Application of Mechanical Ventilation

258 Chapter 9

Nevertheless, arterial blood gases can still provide very useful information when
used in conjunction with other monitoring techniques and thorough patient
assessment.

OXYGEN SATURATION MONITORING

Oxygen saturation is traditionally measured by arterial blood gases. The arterial
oxygen saturation (SaO ) is not always readily available. A simple and noninvasive
2
method to monitor the oxygen saturation is by using a pulse oximeter. The pulse
pulse oximeter: A device
that estimates arterial oxygen oximetry oxygen saturation (SpO ) is less accurate than SaO but it can provide
2
2
saturation (SpO 2 ) by emitting dual quick spot checks or a trend reflecting a patient’s oxygenation status.
wavelengths of light through a
pulsating vascular bed.
Pulse Oximetry
Pulse oximetry has become perhaps the most frequently used method of assess-
ing a patient’s oxygenation status. This noninvasive method measures the ap-
proximate oxyhemoglobin saturation (SpO ). It is non invasive and easy to use.
2
Pulse oximeters may be used intermittently to “spot check” the SpO or continu-
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ously to monitor the patient’s SpO trend. Figure 9-11 shows two portable pulse
2
oximeters.
The pulse oximeter works by emitting dual wavelengths of light through a pulsat-
The SpO 2 reading should ing vascular field. Proper placement of the probe is necessary to obtain an accurate
not be used and reported if
a concurrent low perfusion reading. The heart rate is also measured as the oximeter evaluates each arterial pulse.
alarm is present. If the heart rate on the oximeter varies significantly from the actual pulse as measured
by palpation or cardiac monitor, it could mean low perfusion state or motion artifact.
The SpO reading should not be used and reported if a concurrent low perfusion
2
alarm is present. A good match of actual and oximetry heart rates does not neces-
sarily indicate an accurate SpO reading. The accuracy of the SpO reading should
2
2
be correlated with the patient’s clinical presentation or verified by periodic arterial
blood gases.

© iStockphoto/Photomick © Rob Byron/www.Shutterstock.com

Figure 9-11 Portable pulse oximeters.

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