Use of High-Flow Nasal Cannula Oxygen Therapy in Postanesthetic Brachycephalic Dogs

In the Literature

Jagodich TA, Bersenas AME, Bateman SW, Kerr CL. Preliminary evaluation of the use of high-flow nasal cannula oxygen therapy during recovery from general anesthesia in dogs with obstructive upper airway breathing. J Vet Emerg Crit Care (San Antonio). 2020;30(4):487-492.

The Research …

Postanesthetic hypoxemia can occur due to a patient’s presenting or coexisting morbidity, as well as due to hypoventilation and/or ventilation-perfusion abnormalities associated with residual anesthetic and analgesic agents. Breed idiosyncrasies can worsen respiratory mechanics and lead to further respiratory derangements. Brachycephalic obstructive airway syndrome, which consists of stenotic nares, elongated soft palate, and everted laryngeal saccules, may cause significant negative airway pressure and breathing resistance,¹ potentially contributing to the underlying mechanisms of respiratory dysfunction or hypoxemia.

Although low oxygen flows delivered through typical nasal cannulas have traditionally been used as noninvasive treatment to combat hypoxemia, these systems are associated with adverse effects (eg, desiccation of the nasal mucosa, delivery of variable inspired oxygen levels).² Thus, noninvasive, clinically useful alternatives (eg, high-flow nasal cannula [HFNC] techniques), which have been used to deliver high, positive pressure flows in humans, are beginning to gain favor in veterinary medicine as an alternative to more invasive techniques (eg, tracheal intubation with mechanical ventilation). HFNC equipment is easy to apply and lightweight, is inexpensive, and delivers high-flow, stable, warmed, and humidified inspired oxygen levels via soft nasal prongs that are easily adapted for use in brachycephalic patients (Figures 1 and 2).

FIGURE 1

A 2-year-old, 57.3-lb (26-kg), sedated male English bulldog requiring HFNC oxygen therapy to reduce laryngeal/pharyngeal collapse associated with brachycephalic obstructive airway syndrome. Prongs and tubing are well-adapted to conformation and exhibit condensation associated with the warmed, heated inspiratory flows (A). Tubing traverses behind the ears, where it is easily secured (B). Although difficult to see in this patient, the prong interface size should be ≈50% of the nares occlusion area to allow for nasal leak, potentially reducing any hypercapnia and/or aerophagia.

FIGURE 2

High-flow nasal insufflation product demonstrating the precise delivery of warmed 91.4°F (33°C), high-flow (1 L/kg/minute = 26 L/minute) oxygen. In this case, inspired levels were set at 21% but may be significantly increased to potentially reduce hypoxemia as necessary.

This preliminary study assessed the novel use of HFNC oxygen therapy in postanesthetic brachycephalic dogs to reduce overt clinical signs of dyspnea that may be associated with increased work of breathing and hypoxemia. Although the sample size in this investigation was small and sedation protocols varied among patients, descriptive data indicated that at 30 minutes (n = 5), 60 to 90 minutes (n = 5), and 7 hours (n = 3) after initiation of HFNC oxygen therapy, dyspnea scores and respiratory rates tended to decrease over time, suggesting the application of positive upper airway pressure may have reduced airway resistance and work of breathing. In addition, hemoglobin oxygen saturations remained >95% throughout the study duration.

Although these results appear promising, it is important to recognize there are still issues pertaining to the application of HFNC techniques. For example, aerophagia and air-leak syndrome can be consequences of HFNC, and factors such as the patient’s ability to open-mouth breathe, the flow rate, and cannula positioning and size (which may allow nasal leak) likely affect development of these sequelae, as well as the degree of patient hypercapnia.³ In addition, although the effects of HFNC oxygen therapy have been studied in normal dogs^3,4 and dogs with presenting pathophysiology,⁵ prospective, hypothesis-driven investigations using validated scoring systems are still limited. HFNC oxygen therapy, however, may be a promising, straightforward clinical technique to aid patients with respiratory disorders, including those exhibiting postanesthetic hypoxemia and those with altered airway mechanics.

… The Takeaways

Key pearls to put into practice:

• HFNC oxygen therapy is a simple, noninvasive, and well-tolerated technique that may reduce upper airway obstruction in postanesthetic brachycephalic dogs.

• Although still a novel therapy, HFNC may also be effective in dogs with other respiratory disorders, especially in cases in which traditional nasal cannulation and oxygenation methods are not effective.

• Significant issues associated with HFNC therapy appear to be limited but can include aerophagia, air-leak syndrome, hypercapnia, and patient discomfort requiring sedation.