Brachycephalic obstructive airway syndrome (BOAS) in dogs – Part 1: Stenotic nares repair with a CO₂ laser

By Ziemowit Kudła, DVM, VAT; Poland, Med-Wet, and Anna Nikolajdu-Kudła, DVM For The Education Center
Originally Published In Veterinary Practice News, May 2019 – Download as a PDF

Brachycephalic obstructive airway syndrome (BOAS) is a progressive disorder of the upper airway characterized by primary anatomical abnormalities (e.g. stenotic nares, elongated soft palate, distortion of pharyngeal soft tissues, and a hypoplastic trachea) that increase resistance to airflow and result in restricted breathing.^[1] Restricted breathing, in turn, may lead to pathological changes, such as everted laryngeal saccules, pharyngeal hyperplasia, tonsillar hyperplasia, and eventual laryngeal collapse.^[2] Clinical symptoms of BOAS include snorting, snoring, stridor, dyspnea, exercise intolerance, gagging, gurgling, cyanosis, hyperthermia, and syncope.^[1]

BOAS is most often observed in brachycephalic dogs. Excessive selection for brachycephaly has deformed the upper airway (UA) tract and resulted in obstructions. Breeds most prone to BOAS are French bulldogs, English bulldogs, pugs, Shih Tzus, Pekingese, Boston terriers, Cavalier King Charles spaniels, and boxers. In cats, it is mostly observed in Persians and Himalayans.

The disruption of airflow through the nose means that in order for the affected animal to inhale and achieve sufficient ventilation, it must increase the inspiratory effort to overcome the resistance generated by the upper respiratory tract obstruction. Following Bernoulli’s principle, the acceleration of the airflow through the narrowed nares due to the exerted pressure leads to the approximation of soft structures to each other and inward collapse of the stenotic nares.

Unlike brachycephalic dogs, most dogs with a mesocephalic head structure have nasal openings proportionally large to the size of their larynx. In addition, during rapid breathing (due to excitement, exertion, etc.), mesocephalic dogs are able to actively open their nares, thus improving the flow of air through the nose, something brachycephalic dogs cannot do.

The rapid flow of air in brachycephalic dogs causes tremors of the soft palate, which gradually elongates and thickens. The thickening of the soft palate is another consequence of BOAS. Strong inhalation may lead to deformation and dislocation of the posterior nasal turbinates of the nasopharynx. During a clinical examination of the patient, inspiratory breathing, the extension of the inspiratory phase, and the closing of the dog’s mouth causing deep inspiratory breathing can be observed.

A common growing problem in dogs affected by BOAS is nasal deformation due to an overly large skin fold over the nose, which occurs mainly in pugs (Figure 1).

Further consequences of BOAS syndrome include collapse and/or hypoplasia of the larynx, the collapse of the trachea or even bronchi, displacement of the laryngeal pockets, and inflammatory polyps. These issues will be discussed in subsequent articles within this series. This article mainly focuses on the problem of abnormal airflow through the nose and surgical laser treatment of stenotic nares.

Stenotic nares repair—CO₂ laser procedure

When assessing a dog for BOAS at our clinic, we administer propofol (0.5–1.0 mg/ kg IV) to promote immediate sleep without the effect of sagging tissues. This allows for an accurate evaluation of the whole problem and enables the clinician to plan treatment steps and discuss the options with the owner regarding surgical procedures to be performed, possible complications, and elements that cannot be repaired (Figure 2).

The traditional technique of surgical repair of stenotic nares typically involves cutting only the surface fragments of the nose cartilage as shown in Figure 3. In our experience, such a procedure provides little improvement, as it does not address the problem of nasal obstruction deep inside the nose and does not resolve the lack of necessary mobility in the nasal wings to increase the airflow (as it happens in mesocephalic dogs). We have observed that shortly after a stenotic nares repair procedure is performed this way, the respiratory problem reoccurs or there is little to no improvement and the soft palate can re-elongate within two years post-op. This leads us to think the traditional method is insufficient to resolve the issue.

After 12 years’ experience treating and observing BOAS patients before and after treatments, and attending lectures by well-known veterinarians (Daniel A. Koch, DVM, Diplomate ECVS [European College of Veterinary Surgeons] and Marek Galanty, DVM, PhD), we had a wider perspective of the problem and decided to introduce some modifications to the standard and current surgical procedures.

The first modification in stenotic nares repair is a vertical cut in a rhombus shape (Figure 4). For the procedure, we use a flexible fiber CO₂ laser (Aesculight, Bothell, Wash.) at 15 watts of power in the continuous wave, SuperPulse mode. The adjustable handpiece is set to the 0.25-mm focal spot size. Another modification is cutting the tissue deeper to remove the majority of the cartilage. The incisions are made in the nares cartilage without disturbing the nasal mucosa (Figure 5).

The width of the rhombus depends on the severity of stenosis; its width is adjusted to obtain the best nasal opening after surgery. The introduction of a deep cut through the nares tissue has an important effect: after the sutures have been placed and the nasal mucosa is pulled up, the resulting nasal opening is much larger (Figure 6). This technique reduces the postoperative wound and accelerates healing (Figure 7 illustrates the pre-op [right], intra-op [top], and immediately post-op [left] aspects of the stenotic nares repair). The small scabs that form in the front of the nose do not block the nasal passages during postoperative healing because there is no wound on the inside.

Postoperative care

The patient is much more comfortable than if we had made such a deep and massive traumatic cut through the side of the nasal mucosa. Using monofilament, nonabsorbable suture materials, we typically place three to five individual stitches on each of the nares (Figure 8). Sutures are removed 10 to 14 days postoperatively. The dog is given antibiotics and nonsteroidal anti-inflammatory drugs during the healing period. The patient wears an e-collar until suture removal. Owners often observe an accumulation of small scabs at the incision sites three to five days after the procedure (Figure 9). This does not impede the healing process or significantly impact airflow. It is recommended to remove the discharge that clogs the nasal openings by gently rinsing and washing with water, saline solution, or hydrogen peroxide.

The scar created following the CO₂ laser procedure does not require care after the removal of the sutures. One to three months after the procedure, the nose pigmentation is completely restored and the surgical site is virtually invisible (Figure 10).

Conclusion

For seven years, I have been performing treatments with the Aesculight CO₂ laser and have developed a method of deep vertical cutting that yields the best results for stenotic nares repair. Thanks to the laser’s ability to cut and coagulate simultaneously, the stenotic nares procedure is nearly bloodless, especially compared to the traditional scalpel (Figure 11 shows a side-by-side comparison of an Aesculight laser incision and a scalpel incision).

If an owner comes to us with a dog that snores, has strong dyspnea, and an elongated soft palate, the question is whether it is always necessary to perform the surgery on the nose. The answer is yes, it is. When we consider it in terms of Bernoulli’s principle and a disorder of the airflow through the nose, there is going to be an elongation of the soft palate and further consequences associated with BOAS.

An exception to this situation is the presence of another disturbance of airflow through the nose, such as nasal polyps, nasal cancer, or deformation after injury (i.e. biting or traumatic injury). Therefore, if the respiratory issues (snoring and dyspnea) persist despite previous stenotic nares surgery, it is worth re-analyzing the case from the very beginning. It could be the nares may still be too narrow or it might be necessary to perform another type of nasal examination (rhinoscopy, CT, MRI) to detect internal obstructions of airflow in the nasopharynx.

The future health and well-being of BOAS-prone breeds depend on veterinarians. During the first preventive visit, it is important to talk to puppy owners about BOAS and to suggest a treatment plan before negative consequences associated with the condition develop or worsen. Late surgical intervention may not be as rewarding due to the development of greater complications and secondary problems.

It is necessary to clearly refute the existing myth and explain to dog owners that the sweet snoring of brachycephalic dogs is not a breed trait, but a symptom of a disease.

Ziemowit Kudła, DVM, studied at Poland’s Wrocław University of Environmental and Life Sciences, Faculty of Veterinary Medicine. In 2004, he opened his own veterinary practice in his hometown of Bielsko-Biała, which he runs to this day with his wife, Anna Nikolajdu-Kudła, DVM. Looking for new solutions in veterinary medicine, Dr. Kudła purchased an Aesculight, the first CO₂ laser offered in Poland. Since 2012, he has adapted all surgical procedures in his practice to laser surgery. Kudła is the author of several publications in the national press on the use of the Aesculight CO₂ laser in veterinary practice. He has participated in many conferences, workshops, and courses as a speaker and participant, and lectured on the use of CO₂ laser in veterinary surgery and on veterinary cardiology in Poland. He runs first-aid veterinary courses and courses for dog owners. In 2018, Kudła graduated from the Veterinary Anesthesiology School and received the veterinary anesthesiology technique (VAT) certification.

Anna Nikolajdu-Kudła, DVM, was born in Wrocław, Poland, in 1976. She studied at the Wrocław University of Environmental and Life Sciences at the Faculty of Veterinary Medicine. After graduating in 2004, Dr. Nikolajdu-Kudła and her husband opened their own veterinary practice in Bielsko- Biała, Poland, which they continue to this day. Nikolajdu-Kudła works mainly in the fields of anesthesiology, hematology, and dermatology of dogs and cats. She is the author of several publications in the national press on hematology. Nikolajdu- Kudła has participated in many conferences, workshops, and courses as a speaker and participant, and lectured on the use of CO₂ laser in veterinary surgery and on veterinary hematology in Poland. She runs first-aid veterinary courses and courses for dog owners. In 2018, she graduated from the Veterinary School of Anaesthesiology under the direction of Peter Kronen, Dipl. ECVA.

References

1. Fawcett A, Barrs V, Awad M, et al. Consequences and management of canine brachycephaly in veterinary practice: perspectives from Australian veterinarians and veterinary specialists. Animals. 2019 Jan; 9(1): 3. Published online 2018 Dec 21. doi: 10.3390/ani9010003.
2. Davis MS, Cummings SL, Payton ME. Effect of brachycephaly and body condition score on respiratory thermoregulation of healthy dogs. J Am Vet Med Assoc. 2017 Nov 15;251(10):1160-1165. doi: 10.2460/javma.251.10.1160.

This Education Center article was underwritten by Aesculight of Bothell, Wash., manufacturer of the only American-made CO₂ laser.