Oxygen supplementation
Oxygen delivery to the tissues must be prioritized in any critical patient. It can be maximized by careful consideration of
pulmonary gas exchange, hemoglobin concentration for oxygen transport, and tissue perfusion for delivery of oxygen to the
cells. If respiratory distress is present, it is often very obvious that oxygen supplementation is required. It is important
to recognize, however, that oxygen supplementation may be very beneficial in situations when the presence of hypoxemia might
not be intuitively obvious by observation. Tachypnea may be wrongly attributed to pain when it really is caused by hypoxemia.
Dogs that are flat out because of shock or neurologic involvement may be unable to manifest the typical clinical signs of
respiratory distress. The observation of pink mucous membranes does not rule out the possibility of clinically significant
hypoxemia, since membranes will remain pink until the PaO2 has dropped below 60 mmHg (normal 85-100 mmHg). Similarly, we have great difficulty detecting cyanosis in the animal with
very pale mucous membranes, because insufficient perfusion of the peripheral tissues by blood may preclude the observation
of deoxyhemoglobin. In such situations, we must use other tools to infer a requirement for oxygen supplementation: for example
the presence of refractory tachycardia or hypotension, ventricular arrhythmias, severe mental depression, or tachypnea. The
provision of supplemental oxygen is indicated in every emergency trauma situation, and indeed in every shocky patient until
it has been established that the animal is stable without it. High concentrations of oxygen can be easily achieved by use
of several methods.
Methods of oxygen administration
Several possible methods of oxygen administration are commonly used. Each method has specific advantages and disadvantages,
and different methods often work best in different patients.
Masks, bags, hoods
In each case, oxygen is pumped into a contained area over the head or muzzle of the animal. Most oxygen masks are made of
transparent plastic, through which the animal can be observed. Several methods have been advocated by which increased concentrations
of oxygen can be achieved, including "Flowby" jet-stream canopy O2, placement of a plastic bag over the head into which oxygen is pumped, and the use of an Elizabethan collar with plastic
wrap covering the front.
o Easy to use
o Quickly placed in position in emergency situations
o Depending on flow rates and tightness of fit, very high oxygen concentrations can be achieved
o Because only the head is covered, the clinician can still work with the animal for diagnostic tests or therapeutics
o May not be well tolerated by dyspneic animals
o Not effective in animals that are moving around
o Animals can overheat extremely quickly, especially if they are large and rapidly breathing. The clinician must observe carefully
for evidence of excessive panting and increases in body temperature, which could be very detrimental in the dyspneic animal.
o Carbon dioxide may build up to high concentrations, especially if there is no avenue for outflow from the hood or mask.
Hypercarbia can lead to significant respiratory acidosis.
