Research shows this method will cause significant drying of tracheal membranes within four hours if no humidification is used,
so it is recommended to add this as soon as possible to the administratrion system.
Crowe oxygen collar
This device can be used with a nasal catheter system or used alone as an alternative to nasal tubes for oxygen delivery.
An Elizabethan collar that is one size larger than would generally used is placed, and oxygen is delivered via a tube placed
under the collar and taped to the ventral inside wall of the collar.
Plastic wrap is laid over the ventral 50 percent to 80 percent of the opening and taped in place (Photo 3).
A 2- to 4-liter flow rate generally supplies 50 percent to 60 percent oxygen in two to three minutes. If too much heat and
moisture accumulate in the collar, higher flows can be used. In cats, a 1-liter flow rate generally provides 70 percent to
80 percent oxygen concentrations.
There is research to show that these devices are not very helpful in providing oxygen to patients in very acute conditions.
Although many are used, it is important to remember that, once the patient is placed inside the cage, the patient is truly
isolated from hands-on care. That is not so with the other systems. It also takes more than 20 to 30 minutes to get oxygen
concentrations above 35 percent. Then when the cage door is opened to assess or manage the patient, the oxygen concentrations
fall rapidly to room-air levels unless other supplemental methods are used.
The maximum concentration of >40 percent in these larger "containers" are not recommended by the National Fire Protection
Association because there is significant risk of a flash fire in any oxygen concentrations above 50 percent. Even a spark
caused by the rubbing of synthetic clothing can lead to a catastrophic fire.
Mask with non-rebreathing system attached (anesthetic circle) or new non-rebreathing system that shows much promise
This can be created by using a cone mask attached to either an anesthetic circle system that has a rebreathing bag and unidirectional
valves (within the anesthetic system), or by attaching the cone to a new, commercially available, non-rebreathing system (Bruce
Jones, Las Vegas, Nev.).
This system also can be fitted with either a positive end-expiratory pressure (PEEP) valve or a restrictor assay valve (Photo 4).
If one were just to connect a cone mask to a simple oxygen-supply source, without the unidirectional valves and reservoir
bag, the system would be very inefficient, capable of achieving only up to 40 percent oxygen. During exhalation, carbon dioxide
would become trapped in the mask, and during inhalation it would be rebreathed.
If the mask is fairly airtight, the speed of inhalation and the volume needed will surpass the volume within the mask and
the work of breathing will be increased substantially,
An oxygen sensor is a small photo-sensor that measures the amount of oxygen in the atmosphere. It is appropriate to use any
time we are providing oxygen to our ICU patients so the oxygen concentrations being delivered can be known (Photo 5).
They are easy to calibrate and use. There are several available commercially.
Although high oxygen concentrations >80 percent are recommended in acute conditions, levels over 60 percent given for over
24 hours are associated with dysfunction of the type II cells that produce surfactant.
Without measuring oxygen concentrations one cannot know the effectiveness, nor the danger, of an oxygen supplementation system.
It is recommended to monitor the percent of oxygen over time with each method of delivery.
This was done in one research study that compared oxygen concentrations reached over time with various methods (Photo 6).
In cases where cannula or catheters are used, the exhaled gas analyzed can be used to approximate the inhaled oxygen concentration.
In these cases 4 percent is subtracted to estimate the inhaled concentration.
Crowe is chief of staff, Pet Emergency Clinics and Specialty Hospital, Thousand Oaks and Ventura, Calif. Call him at (706)
296-7020 or e-mail him at firstname.lastname@example.org