Hot Literature: New support for supplemental oxygen flow rates in foals

In a recent study published in the American Journal of Veterinary Research, Iowa State University researchers delved into the art of administering supplemental oxygen to neonatal foals. The practice of providing supplemental oxygen to neonates is nothing new, but understanding the physiologic effects of oxygen given via nasopharyngeal cannula has not been studied extensively. The study looked at the changes in the fraction of inspired oxygen concentration (FiO2), oxygen saturation of hemoglobin in arterial blood (SaO2), partial pressure of oxygen in the blood (PaO2), and other variables at various oxygen flow rates administered either unilaterally or bilaterally.

Nine healthy neonates ranging from 3 to 5 days of age were used in the study. Aside from receiving a single dose of sedation for arterial catheter, nasotracheal tube, sampling line, and cannula placement, no other medications were administered. After baseline arterial blood sampling, each cannula was connected to a flow meter, humidifier, flow splitter, and high-pressure oxygen tank. The foals were closely monitored during the three-hour experiment for any evidence of adverse effects. They were allowed to remain standing with the mares throughout the experiment, and minimal physical restraint was used. If any of the foals became excited or agitated, they were given time to relax before proceeding with the experiment.

Unilateral and bilateral flow rates of 50, 100, 150, and 200 ml/kg/min were evaluated. No adverse effects were noted, but at the highest flow rate, foals became agitated. Relevant to the equine veterinarian, the PaO2, FiO2, and SaO2 increases documented were both clinically significant and dose-dependent. This may help provide dosage guidelines for ill neonates as well as expected changes in PaO2 and FiO2 in healthy foals given supplemental oxygen in this manner.

Encountering hypoxemic neonatal foals is not uncommon in clinical practice. Providing supplemental oxygen through a face mask, a transtracheal catheter, or endotracheal intubation and mechanical ventilation can cause a significant degree of discomfort and may not be practical or cost-effective in some circumstances. A nasal cannula is likely the most inexpensive and least irritating of the available methods. The data reported here suggest that it is also a highly effective means of administering supplemental oxygen with dose-dependent results. However, further evaluation to better understand the effects of these methods and flow rates on foals with respiratory compromise is needed. The authors further caution that the response to oxygen administration is best evaluated by monitoring blood gas values and the patient’s clinical response.

Wong DM, Alcott CJ, Wang C, et al. Physiologic effects of nasopharyngeal administration of supplemental oxygen at various flow rates in healthy neonatal foals. Am J Vet Res 2010;71(9):1081-1088.

Link to abstract: http://avmajournals.avma.org/doi/abs/10.2460/ajvr.71.9.1081