Page 87 - Basic Monitoring in Canine and Feline Emergency Patients

VetBooks.ir

Fig. 4.10. A pulse oximetry unit (Massimo, Irvine, California, USA) displaying a plethysmographic tracing similar to an
arterial waveform reading (red arrow). The waveform depicted in this image represents a good tracing and if the heart
rate shown here matches the patient, the pulse oximetry reading is likely to be accurate barring other confounding
variables (see Table 4.2).

Fig. 4.11. A pulse oximeter displaying a weak waveform (red arrow). It is important to note in this photo that while the
pulse oximetry value of 100% and a heart rate of 58 bpm are possibly within the normal reference range for a dog, the
probe was not actually connected to a patient while it was displaying the readings shown in this photo, displaying a
likely motion or time-delay artifact. This underlines the importance of ensuring a good waveform or signal quality along
with heart rate on all patients prior to looking at the pulse oximetry reading.

oxygen supplementation. Similarly, anemic patients Patients with normal pulse-ox values (with
may have a normal pulse-ox reading but still be in strong signals that match their heart rates on the
need of oxygen to deliver to the tissues. monitor, i.e. that are ‘believe-able’) should be sus-
pected of having these ‘look-alike’ causes of tachyp-
nea. Patients with ‘believe-able’ pulse-ox values
<95%, with poor pulse-ox signals, or who have
4.3 Indications for Pulse Oximetry significant signs of respiratory abnormalities
despite normal readings (e.g. significant work of
Patients frequently present to the emergency depart- breathing, abnormal upper airway noises, etc.)
ment for clinical signs consistent with respiratory dis- should be considered possibly hypoxemic until
tress. In that setting, it is important to differentiate proven otherwise. Supply these patients with oxy-
between true hypoxemia and other conditions that can gen while additional diagnostics are performed to
also cause a rapid respiratory rate such as pain, fear, address the underlying cause.
stress, or acidosis. Pulse oximetry is a fast, minimally If you are unsure if a patient is suffering from
invasive way to screen for hypoxemia in these patients. hypoxemia or are unable to believe the pulse-ox

Pulse Oximetry 79