Objective: To determine the amount of time required to reach the highest concentrations of oxygen at the patient's face and to determine what these highest concentrations of oxygen were with various non-invasive methods of providing supplemental oxygen using a commercial oxygen content analyzer.
Procedure: Three healthy cats and 3 healthy dogs were each individually given supplemental oxygen by 6 different means, each done at 2 rates (5 L and 15 L per minute). The methods tested were: 1) Plastic sheet over conventional cage door (PSCD); 2) Blow-by where the tubing delivering the oxygen was held 8 cm from the face (BB); 3) Large plastic bag covering the patient (BAG); 4) Anesthesia induction chamber (AIC); 5) Synder oxygen cage (SOC); and 6) Crowe Oxygen E-Collar (COC). Prior to the testing, the commercial oxygen content analyzer (Mini-Ox) was calibrated.
Results: Significant repeatable differences were consistently observed between the 6 methods of oxygen delivery. Results of both 5 L and 15 L/min oxygen flow rates consistently indicated that the highest oxygen concentrations were achieved with the anesthesia induction chamber and large plastic bag with oxygen concentrations reaching approximately 95% and 90%, respectively between 5 to 15 min. The BAG method had the advantage of allowing additional room for patient manipulation and the ability to place intravenous catheters while continuing to give supplemental oxygen. The plastic sheet covering a conventional cage door provided oxygen concentrations of 50% and 60% at 15 and 45 min, respectively. The Crowe Oxygen E-Collar achieved oxygen concentrations of 70% in 1.5 min. Blow-by was found to be the simplest method. It increased FiO2 to 40% within 2 min. The Synder oxygen cage was able to achieve 45% oxygen concentration within 30 min with an oxygen flow rate of 15 L/min. It was able to achieve 60% at 45 min (similar to the plastic bag on the cage).
Conclusion: The order of effectiveness of providing non-invasive oxygen supplementation, from the highest to the lowest concentrations, was AIC, BAG, COC, PSCD, SOC, and BB. The fastest to the slowest increases in oxygen concentrations followed the same order at both 5 L and 15 L/min oxygen flow rate and they were BB, COC, AIC, BAG, PSCD, and SOC. SOC was the most inefficient means of providing oxygen while AIC, BAG and COC were the most efficient.