Page 86 - Basic Monitoring in Canine and Feline Emergency Patients

used intrarectally (pointed dorsally against the
sacrum) can be used in asleep or awake patients
VetBooks.ir depending on temperament. The advantage to
reflectance probes is that they are sometimes better
tolerated in awake animals for longer-term use (i.e.
taped to the underside of a tail on a patient in the
oxygen cage), and can be used on smaller patients
where the larger transmission probe clips are too
bulky for use. There is less pressure on the tissues
than with the transmission probe clips as well,
which may allow for longer use without occlusion
of the arterial blood flow.

Gauging the accuracy of the
pulse-ox readings
Accuracy of pulse oximetry results are generally
gauged by observing the output on the pulse oxi-
meter and correlating it to the patient. It is essential
that probe is receiving a strong pulsatile blood flow
signal. The signal quality can be reported on the
pulse oximeter in a few different ways depending Fig. 4.8. A pulse oximetry unit (Massimo, Irvine,
on the unit used. In some monitors the signal qual- California, USA) demonstrating poor signal quality
ity can be shown by bar indicators, where the (SIQ) as shown by the red arrow.
greater number of bars, the better the signal quality
(Figs 4.8 and 4.9). Other types of monitors display
the actual plethysmographic tracing, similar to an
arterial pressure waveform (Fig. 4.9). If the pulse
oximeter displays a good-looking uniform wave-
form or high signal quality, it is more likely to be
accurate (Figs 4.8 and 4.9).
To confirm the waveform is actually detecting
the arterial pulse, the heart rate displayed on the
pulse-ox should always be matched to the heart
rate detected by an independent method (ausculta-
tion, pulse palpation, ECG, etc.) Any pulse oxime-
try reading in which the heart rate displayed on the
machine does not match the patient’s heart rate
should be considered inaccurate (Figs 4.10 and
4.11). When initially attaching a pulse oximetry
probe it is important to remember that it takes
several heart beats for the sensor to assess the data
from multiple waveform peaks, so the results are
not instantaneous.
The results obtained from the pulse oximeter
should always be correlated to the clinical status of
the patient. For example, a patient who appears to
be in significant respiratory distress with a pulse
oximetry reading of 100% should ideally have Fig. 4.9. A pulse oximetry unit (Massimo, Irvine,
their oxygenation status confirmed by an arterial California, USA) receiving good signal quality (SIQ) as
blood gas before deciding that they do not need shown by the red arrow.

78 K.A. Marshall and A.C. Brooks