Abstract

Portable battery driven oxygen concentrators provide an alternative to the use of oxygen cylinders for treatment of hypoxemia during field anesthesia. We evaluated use of the EverGo™ Portable Oxygen Concentrator (Respironics^®, Murrysville, Pennsylvania, USA) with fixed bolus delivery for improvement of arterial oxygenation during anesthesia of wildlife. This concentrator is a bolus driven device which delivers oxygen in a pulsed flow (pulse volume 12–70 ml) with a maximum capacity of 1.05 L/min. The pulse dose setting shall be adjusted according to the respiratory rate (RR) of the animal (e.g., setting 6 for a RR ≤15/min). The study included 16 free- ranging brown bears (Ursus arctos), seven free-ranging bighorn sheep (Ovis canadensis), and five captive reindeer (Rangifer tarandus). Oxygen was administered via two nasal lines that were inserted through the nostrils to the level of the medial canthus of the eyes. Arterial blood samples were collected before and during oxygen therapy and immediately processed with an i-STAT^® Analyzer (Abbott Laboratories, Abbott Park, Illinois, USA). When providing oxygen from the portable concentrator, the arterial oxygenation markedly improved in brown bears and reindeer, whereas no improvement was seen in the bighorn sheep. The efficacy of the evaluated method may be influenced by ambient temperature, altitude, pulse dose setting on the concentrator, the animal’s respiratory rate, and species-specific physiology during anesthesia (e.g., shunt fraction). Portable concentrators are user friendly, non-explosive devices that are rechargeable and produce oxygen at low cost, but further studies are needed to evaluate their efficacy in different species and capture settings.