By Ziemowit Kudła, DVM, VAT; Poland, Med-Wet, and Anna Nikolajdu-Kudła, DVM For The Education Center
Originally Published In Veterinary Practice News, February 2020 – Download as a PDF
In part 1 of the series on brachycephalic obstructive airway syndrome (BOAS) in dogs (see VPN May 2019), we described the first stages of its development (i.e. nares stenosis) and the problems and treatments associated with it. This time, we will look at other consequences of BOAS, specifically how increased pressure caused by breathing through the narrowed nares and Bernoulli’s law leads to secondary changes of the airway, such as elongation of the soft palate, laryngeal collapse, eversion of laryngeal saccules, inflammatory polyps, and even trachea collapse.
Due to the increased pressure related to airflow through the nasal cavity, the soft palate gets pulled into the larynx. As a consequence, the soft palate becomes elongated, obstructing the airway and creating a long fold, which leads to snoring and a significant reduction in airflow (Figure 1). Elongation of the soft palate can be extensive (Figure 2), greatly affecting the patient’s clinical condition. Further, it may lead to inspiratory dyspnea. Because this is a consequence of the narrowed nares, a certain relationship can be observed: the more narrowed the nares and increased disturbance of the airflow are, the faster the soft palate elongates, thus accelerating the onset of snoring and other signs of respiratory problems. We are already observing cases of BOAS in three-month-old puppies whose nares are so narrowed, they are unable to breathe, eat, and function normally. In such affected puppies, we also see a slightly elongated soft palate (Figure 3). Dogs with mild stenosis of the nares develop an elongated soft palate and symptoms associated with it later in life, roughly at four to five years of age.
At our clinic, surgical repair of the elongated soft palate (staphylectomy) is performed utilizing a CO2 laser. Laser staphylectomy results in only minor bleeding. This allows for palatal muscle resection and simultaneous muscle thinning without the need for surgical sutures (Figures 4 and 7).
Laser equipment and settings
CO2 surgical laser (10.6 μm) with a flexible hollow waveguide and a tipless (0.25-mm spot size) handpiece (by Aesculight, Bothell, Wash.). Initial marking is performed with the laser set to 15 watts in the single-pulse mode. For resection, the laser is set to 12 to 15 watts in the continuous wave, SuperPulse mode.
The dog is placed in sternal recumbency, and the head is suspended by the maxilla with a special hanger (Figure 5). The patient is sedated with Dexdomitor. Anesthesia is induced with propofol. Fentanyl is administered intravenously, while metamizole and meloxicam are administered subcutaneously. The patient is intubated and anesthesia is maintained with isoflurane or sevoflurane gas on the mechanic respirator system. Saline-soaked gauze is placed behind the soft palate to protect the back of the throat and the endotracheal tube.
To determine the proper amount of soft palate to be excised, we mark the planned incision with the laser approximately at the mid-tonsil height level. This line should be arched, reflecting the shape of the edge touching the epiglottis (Figure 6).
First, the soft palate mucosa is incised from the lingual side (Figure7). Using surgical Allis tissue forceps, the pendulous section of the soft palate is gently retracted rostrally and ventrally, and an initial incision is made across the soft palate along the marked line. Further incisions are made from left to right, gradually cutting the palatal muscle at an angle to obtain the maximum possible thinning of the muscle (Figure 8). Traction facilitates laser incision. After the excess tissue is removed, the clinician should assess the surgical site for bleeding. Typically, no sutures are necessary, as the CO2 laser seals smaller blood vasculature, which usually ensures a lack of hemorrhage postoperatively.
The clinician should be careful when removing tissue near laryngeal saccules. Special attention should also be paid to the palatine arteries. In larger breeds, such as the English bulldog, Bernese Mountain Dog, and Newfoundland, and especially when the problem has existed for a long time (e.g. a few years), the soft palate is thickened significantly and contains large blood vessels that may require ligation (we utilize absorbable multifilament 4-0 suture material).
Normally the staphylectomy procedure takes four to five minutes. Postoperative recovery is usually smooth and healing progresses without complications.
Postoperatively, the patient is given antibiotics according to the antibiogram we use from a swab taken from the larynx during diagnostics a few days earlier. The patient is also given meloxicam, metamizole, and fentanyl.
For patients who preoperatively had problems with vomiting, we add antiemetics (maropitant) and medications for stomach mucosa (ranitidine, etc.).
The patient remains under our care until the next day. Before being discharged, he or she is given analgesics (meloxicam, metamizole) and antibiotics in injection form. The owner is instructed to give the patient analgesics in the tablet form (carprofen, cimicoxib, firocoxib, or meloxicam) for five days and an antibiotic for 10 days, depending on the bacterium obtained from the larynx culture. The patient returns for a follow-up exam at 10 to 14 days post-op.
Other BOAS-related airway problems
In some cases, the soft palate is so thickened that its edges spread to the sides of the throat, extending into the larynx. During staphylectomy, these folds should also be corrected, as they may later lead to postoperative complications, causing inspiratory dyspnea (feeling of shortness of breath).
Long-lasting inspiratory dyspnea with a full set of BOAS complications may lead to the formation of a pathologically hanging fold on the posterior wall of the nasopharynx, which as a result of air pressure (Bernoulli’s law) falls like a curtain covering the laryngeal opening from the top (Figure 9). This is one of the factors reducing the effectiveness of staphylectomy. We correct this fold by making a transverse cut over the larynx (the CO2 laser is utilized with the same settings as for the soft palate resection) so that the cutting line is located behind the upper edge of the larynx toward the esophagus.
One of the frequent symptoms of BOAS is the enlargement and/ or inflammation of the tonsils. Therefore, before the staphylectomy procedure (before inserting the endotracheal tube), we perform a bacteriological swab from the larynx and sometimes also from the tonsils. Patients coming to us for surgery have repeatedly been subjected to inexpedient antibiotic therapy and steroids, which may contribute to inadequate healing after surgery. Bacteria, such as Escherichia coli, Staphylococcus aureus, and Klebsielle pneumoniae (usually extended-spectrum beta-lactamase – [ ESBL- ] positive), are often isolated from that area. We often need to perform laser tonsillectomy to remove pathologically altered tonsils. However, this surgical laser procedure is reserved for unsuccessfully treated cases of nares and soft palate correction, and is performed only after targeted antibiotic therapy and when hypertrophy is still observed.
Bacterial complications often present as erosions on the hard and soft palate (Figure 10). Purulent tonsils can extend to the soft palate, creating extensive inflammatory changes. This frequently occurs in Cavalier King Charles Spaniels and is referred to in the histopathological examination as eosinophilic inflammation.
Another problem observed in dogs with BOAS is the high base of the tongue (Figure 11), which, in some breeds (e.g. Boston terrier and pug), reduces the airway space, leading to the development of inspiratory dyspnea. This is often the reason for the lack of success after surgical treatment, despite the properly performed stenotic nares surgery and staphylectomy. At present, the problem of a high tongue base cannot be resolved surgically due to the highly traumatic nature of the procedure and the risk of lingual paralysis. We are currently conducting research on this issue, using imaging analysis (RTG, MRI, CT) of the tongue in brachycephalic dogs before and after BOAS surgery to determine how big this problem is and how it affects BOAS surgeries.
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. ECV.
This Education Center article was underwritten by Aesculight of Bothell, Wash., manufacturer of the only American-made CO2 laser.