High-flow nasal oxygen therapy reduces work of breathing without altering systemic oxygen delivery or consumption in healthy, anesthetized, spontaneously breathing dogs.

HFNOT at 2 L/kg/min safely reduces work of breathing in anesthetized dogs without affecting systemic oxygen delivery.

This prospective, randomized, crossover study investigated the effects of high-flow nasal oxygen therapy (HFNOT) on work of breathing (WOB) and systemic oxygen balance in six healthy, anesthetized Beagles under alfaxalone total intravenous anesthesia. Dogs received HFNOT at 0 (control), 1, or 2 L/kg/min with room air (FiO2 0.21) in randomized order with ≥7-day washout periods. WOB was assessed using esophageal pressure-derived indices, including esophageal pressure swing and esophageal pressure-rate product. Systemic oxygen balance was evaluated via oxygen delivery index, oxygen consumption index, and oxygen extraction ratio using Fick-derived methods combined with thermodilution cardiac output measurements. At 2 L/kg/min, esophageal pressure-rate product decreased significantly from baseline (134.9 ± 49.7 cm H2O·breaths/min) to approximately 50–55 cm H2O·breaths/min at all post-initiation time points. Esophageal pressure swing also decreased at 10 minutes post-initiation. Respiratory rate declined during both 1 and 2 L/kg/min sessions. Importantly, oxygen delivery index, oxygen consumption index, oxygen extraction ratio, arterial oxygen saturation, and mixed venous oxygen saturation remained stable across all flow rates and time points, indicating no adverse effects on systemic oxygen metabolism. These findings demonstrate that HFNOT at 2 L/kg/min effectively reduces surrogate indices of respiratory effort through mechanical rather than metabolic mechanisms. This supports the physiological safety of HFNOT in anesthetized dogs and suggests potential clinical utility for reducing respiratory effort in veterinary patients without compromising oxygen homeostasis.

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