All about upper airway diseases
Upper airway diseases are some of the most common respiratory conditions we see in practice. From the huge influx of brachycephalic patients needing corrective surgery, to the patients with sneezing and nasal discharge needing to be investigated, a big part of the veterinary nurse’s role is caring for these patients.
Today we’re walking through some of the most common upper airway conditions we encounter in practice, and chatting about why we see them, which patients they affect, and how to care for these patients as nurses.
The upper airway
The upper airway includes all the structures cranial to the trachea – including the larynx, pharynx and nasal cavities. The larynx protects the lower airway from aspiration of food/water and produces the voice.
The most common upper airway conditions we see in practice include brachycephalic obstructive airway syndrome, laryngeal paralysis and nasal/nasopharyngeal diseases such as neoplasia, nasopharyngeal stenosis and chronic rhinitis.
BOAS
Brachycephalic obstructive airway syndrome, or BOAS, is seen in brachycephalic breeds such as French Bulldogs, English Bulldogs, Pugs, Shih Tzus and Boston Terriers. However, it’s not just dogs we see this condition in, and Persians and Exotic Shorthaired cats are also commonly affected.
Pathophysiology
BOAS includes several congenital abnormalities of the upper airway - stenotic (narrowed) nares, an overlong and thickened soft palate and additional pharyngeal tissue. These abnormalities cause varying degrees of airway obstruction and resultant dyspnoea. The chronic airway obstruction seen in these patients also causes secondary or acquired changes, such as eversion of the laryngeal saccules and inflammation of the soft palate/pharyngeal tissues. This causes further oedema/thickening of these tissues, contributing to obstruction and dyspnoea.
Clinical Signs
Clinical signs include increased respiratory effort on inspiration, exercise intolerance, inspiratory stridor and/or coughing and gagging. The condition is usually progressive if untreated.
Diagnosis
Direct examination of the upper airway is used to diagnose the condition; it is treated surgically, with resection of the nares and soft palate and removal of the everted saccules (if required).
Nursing Care
In the postoperative period, the patient should be kept calm, and excessive vocalisation should be avoided, since this can worsen any oedema of the surgical site, resulting in airway obstruction.
Sedation may be required post-operatively to ensure the patient remains calm.
Due to the handling and resection of the upper airway structures, oedema and airway obstruction is a risk post-operatively. An emergency airway kit should be kept with the patient in recovery from the procedure; this should include an induction agent, a laryngoscope, a variety of endotracheal tubes (including very small sizes) and a tracheostomy tube/kit. Oxygen administration should continue until complete recovery from anaesthesia and pulse oximetry should be utilised for as long as the patient will tolerate it in recovery.
Laryngeal Paralysis
Laryngeal paralysis is the unilateral or bilateral paralysis of the muscles responsible for moving the arytenoid cartilages in the larynx.
It can be acquired or congenital, and typically affects middle-aged-to-older, large breed dogs, particularly Labrador or Golden Retrievers. Acquired paralysis can be idiopathic, or secondary to laryngeal trauma or injury, diseases affecting the laryngeal nerve, or polymyopathy/myasthenia gravis.
Clinical Signs
Clinical signs include inspiratory noise (stridor) and exercise intolerance; gagging and coughing may also be seen. These signs may appear worse in the heat, and often clients will notice clinical signs heading into the summer months.
Diagnosis
Direct examination of the larynx is used to diagnose the condition; this should be performed under sedation or very light anaesthesia, ensuring that the agents used do not depress spontaneous respiration or cause apnoea.
The arytenoid cartilages should be observed using a laryngoscope. Normally, both cartilages move symmetrically and promptly during inspiration.
During the examination, the head is held by an assistant as if for endotracheal intubation. The assistant should observe the patient’s respiration and advise the examiner as each breath is seen, so the examiner can determine if the laryngeal cartilages are moving with each breath.
Thoracic radiography is advised in these cases, to exclude any concurrent aspiration pneumonia or other conditions such as megaoesophagus (associated with myasthenia gravis).
Emergency Management
These patients may present in acute respiratory distress. In these cases, management with oxygen supplementation and anxiolysis with sedative agents (as distress can increase respiratory effort, worsen dyspnoea, and increase oxygen demand) may be indicated. Venous access should also be secured as soon as possible. Attention should be paid to the patient’s temperature, and hyperthermia should be avoided/treated if seen.
Treatment
In mild or unilateral cases, medical management may be attempted prior to surgical correction; this involves management of the patient’s weight and exercise level.
Surgical correction may be required in severe or bilateral cases; this is typically performed via a procedure called unilateral arytenoid lateralisation, or a laryngeal tieback.
Nursing Care
These patients should be monitored closely in the postoperative period to ensure aspiration pneumonia does not develop; food and water should be withheld until the patient is fully awake, and slow/gradual feeding with small meatballs of food may be indicated (this should continue after discharge until complete healing has occurred). Similarly to BOAS patients, oxygen supplementation should continue into recovery and an emergency airway kit should be on hand.
Nasal/Nasopharyngeal Disease
Nasopharyngeal or nasal disease may be seen due to several causes, including foreign bodies, neoplasia, bacterial, viral and fungal infections, nasopharyngeal polyps or nasopharyngeal stenosis.
These patients often present with a history of increased expiratory noise (stertor) and unilateral or bilateral nasal discharge. Changes to the bone conformation around the nose may also be seen.
Diagnosis
Diagnostic tests include imaging of the nasal cavity (radiography or computed tomography), where turbinate bone destruction and fluid and/or soft tissue within the nasal passages and sinuses may be seen; if using CT, the administration of IV contrast medium can highlight any vascular/neoplastic lesions. Endoscopic examination of the nasal cavity and nasopharynx is also used to guide diagnosis and treatment; this allows guided biopsies to be taken, evaluation of any fungal plaques, and removal of any foreign material, as well as flushing of the nasal cavity, to remove fluid/mucous accumulation. Nasal endoscopy is usually performed via rostral rhinoscopy using a rigid rhinoscope, and a flexible bronchoscope which is retroflexed to examine the caudal nasopharynx. This examination with a flexible bronchoscope allows us to easily see nasopharyngeal polyps, foreign bodies or stenosis.
Treatment
Treatment of nasal/nasopharyngeal disease varies depending on the cause.
In cases of neoplasia, chemotherapy or radiotherapy may be considered depending on the type of tumour.
Fungal infection such as Aspergillus is normally treated with the administration of antifungals such as clotrimazole directly into the sinuses, or administration of systemic antifungals.
Bacterial rhinitis is treated with appropriate antibiotic agents based on culture and sensitivity results.
Viral rhinitis or chronic rhinosinusitis is a life-long condition managed with nebulisation, treatment of any concurrent bacterial infection, +/- systemic antivirals such as famciclovir in cases of feline herpesvirus-1. Intermittent nasal flush procedures under general anaesthesia may also temporarily relieve clinical signs.
Nursing Care
Nursing considerations for the nasal disease patient include nebulisation with 0.9% Saline to help loosen accumulated mucous in the nasal cavities, regular clearing of nasal discharge and face washing/grooming (since these patients are often not keen/able to do this themselves), encouraging voluntary food intake (by offering warmed, smelly foods which are highly palatable, since patients may not be able to smell their food normally), monitoring hydration and providing fluid therapy if required, and monitoring pain/comfort levels and providing analgesia as appropriate.
So that’s a brief overview of some of the most common upper airway conditions that we see in practice. Want to know more about respiratory patient care? Head over to the Instagram page for more respiratory nursing tips and tricks!
References
Merrill, L. 2012. Small Animal Internal Medicine for Veterinary Technicians and Nurses. Iowa: Wiley-Blackwell.
Tonozzi, C. 2021. The Respiratory System in Animals. MSD Veterinary Manual. Available from: https://www.msdvetmanual.com/respiratory-system/respiratory-system-introduction/the-respiratory-system-in-animals
