Introduction: Heated, humidified, high-flow nasal cannula oxygen therapy (HFNC) is an intermediate method for providing oxygen supplementation as well as promoting improved respiratory function. HFNC offers provision of continuous positive airway pressure via high gas flow rates. Successful application of HFNC to hypoxemic respiratory failure patients would provide a noninvasive level of intermediate support that has not previously been possible in veterinary patients.

Objective: To determine the effect of HFNC oxygen therapy on cardiopulmonary variables and outcome, in canine patients with acute hypoxemic respiratory failure.

Methods: This was a prospective, sequential clinical trial at a university veterinary teaching hospital. HFNC therapy was initiated in dogs with hypoxemic respiratory failure after 30 minutes on traditional oxygen supplementation failed to: increase SpO2>96%, PaO2>75 mm Hg, or improve respiratory rate/effort. Physiological variables, blood gas analysis and dyspnea/sedation/tolerance scores were collected prior to HFNC initiation (on traditional oxygen support (time 0 or T0)), and subsequently during HFNC oxygen administration at time 30, 60 minutes and 7±1 hours.

Results: Twenty-two client-owned dogs that failed traditional oxygen support were enrolled in the study between July 2016 and January 2018. Relative to T0, use of HFNC resulted in a decreased respiratory rate at 1 hour (p=0.022) and 7 hours (p=0.012), a decrease in dyspnea score at all times (p<0.01), and an increase in SpO2 at all times (p<0.01). There was no difference in arterial/venous PCO2 relative to T0, though PaCO2 was correlated with flow rate. Based on respiratory assessment, 60% of dogs responded to HFNC use by 30 minutes and 45% ultimately responded to HFNC use and survived. No clinical air-leak syndromes were observed.

Conclusions: HFNC use improved oxygenation and work of breathing relative to traditional oxygen therapies, without impairing ventilation. HFNC use appears to be a beneficial oxygen support modality to bridge the gap between standard oxygen supplementation and mechanical ventilation.