Study suggests HFNOT lowers breathing effort in anesthetized dogs: full analysis

High-flow nasal oxygen therapy, or HFNOT, reduced work of breathing in healthy, anesthetized, spontaneously breathing dogs without measurably changing systemic oxygen delivery or oxygen consumption in a new study from the American Journal of Veterinary Research. The paper, published April 27, 2026, tested whether HFNOT has physiologic effects beyond oxygen supplementation, and the answer appears to be yes: higher flow rates changed esophageal pressure patterns and lowered respiratory rate, even though oxygenation and cardiovascular delivery variables stayed stable. (vetlit.org)

That question matters because HFNOT has been gaining traction in veterinary medicine as a noninvasive respiratory support option between conventional oxygen therapy and more invasive ventilation. A 2023 clinical review described HFNOT as an alternative that can deliver heated, humidified gas at high flow rates and more predictable FiO2 than standard low-flow methods, while veterinary studies to date have focused largely on feasibility, tolerance, oxygenation, and use in hypoxemic respiratory failure. Earlier work in dogs found that HFNC was feasible and safe in healthy animals, and review authors noted that flow rates around 1 to 2 L/kg/min can generate positive airway pressure in many dogs. (frontiersin.org)

In the new crossover study, six healthy adult Beagles underwent alfaxalone total IV anesthesia and received HFNOT at baseline, 1 L/kg/min, and 2 L/kg/min, with measurements including esophageal pressure, respiratory parameters, cardiovascular variables, and arterial blood gases. According to the abstract, both end-expiratory and end-inspiratory esophageal pressures increased in a flow-dependent manner. Mean arterial pressure increased modestly at 2 L/kg/min versus baseline, but cardiac index did not change across flow rates. Respiratory rate fell from 18 ± 6 breaths/min at baseline to 11 ± 3 breaths/min at 2 L/kg/min, and arterial blood gas values were not different across conditions. The authors concluded that HFNOT increased esophageal pressure without cardiovascular compromise and reduced respiratory rate without altering arterial blood gas values. (researchgate.net)

Those findings line up with the broader HFNOT literature, which has suggested the therapy can do more than improve oxygen concentration. The 2023 Frontiers review noted that, in both human and veterinary settings, high-flow systems may reduce respiratory rate and work of breathing through mechanisms that include positive airway pressure and washout of upper-airway dead space. In dogs recovering from anesthesia, previous prospective work also found generally good tolerance across tested temperatures and flow rates, though occasional intolerance has been reported. (frontiersin.org)

There doesn’t appear to be broad outside commentary on this specific paper yet, but the study fits with an emerging veterinary view of HFNOT as a supportive modality that may help selected patients before intubation becomes necessary. In clinical studies summarized by the Frontiers review, dogs with acute hypoxemic respiratory failure that failed conventional oxygen therapy often showed improved oxygenation after transition to HFNOT, although outcomes were mixed and many severe cases still required escalation or did not survive because of underlying disease severity. That context is important: the new AJVR paper is mechanistic, not outcomes-based, and it was conducted in healthy dogs under controlled anesthetic conditions. (frontiersin.org)

Why it matters: For veterinarians, especially those in emergency, critical care, and anesthesia, the study helps clarify what HFNOT may actually be doing at the bedside. If high flow reduces breathing effort without materially affecting systemic oxygen delivery or consumption in stable anesthetized dogs, clinicians may think of the therapy not only as an oxygen-delivery tool, but also as a way to alter respiratory mechanics. Still, the small sample size, crossover design, and use of healthy Beagles limit how far the findings can be generalized. Dogs with pneumonia, brachycephalic airway disease, pulmonary hypertension, or severe dyspnea may respond very differently, and clinical benefit will still depend on tolerance, staffing, equipment, monitoring, and timely escalation when HFNOT is not enough. (researchgate.net)

What to watch: The next phase for this line of research is likely to focus on clinical populations rather than healthy models, including whether changes in esophageal pressure and respiratory rate correlate with lower intubation rates, better comfort, or more targeted flow prescriptions in dogs with respiratory disease. Given the growing veterinary literature around HFNOT protocols and case use, expect future work to push toward patient selection, monitoring standards, and clearer decision points for when to escalate beyond noninvasive support. (frontiersin.org)