More studies needed [Small Animal Oxygen Therapy]

In the otherwise excellent article, “Small Animal Oxygen Therapy” by Dr.M.Camps-Palau et al (July 1999), it is mentioned that the use of the face mask may result in CO2 retention and that of the Elizabethan Collar Canopy (ECC) may also result in hyperthermia, high humidity and O2 leakage. In our studies in healthy, anaesthetised dogs (Aust Vet Pract 26(4): 199), the ECC was not associated with any complications. An arrow like (trap-door) opening made to the cover at the top of the tightly placed collar proved adequate in avoiding retention and build up of CO2 inside the canopy and allow the escape of humid and warm air. The only disadvantage that we observed was the amont of time required for the canopy to be placed and become enriched in oxygen, so we would agree with the authors that an initially high O2 flow rate is needed to quickly fill the canopy.

With the face mask, CO2 levels were greater in all subjects in our study (Aust Vet Pract 27(1): 34) when very low flow rates when used, but only rose considerably in one subject. This may be partially attributed to CO2 retention within the face mask as a result of limited entrainment of room air or the fact that oxygen administration is more efficient with the mask. In the latter case, the resulting increase in FIO2 affects the respiratory center that repsonds to hyperoxia with CO2 retention.

Finally, some of the recommendations made for optimal O2 flow rates are based on anecdotal evidence, a fact that highlights the need for further studies dealing with the comparative effectiveness of oxygen therapy methods in a clinical setting.