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July 2024
Snuffle, Cough, Snort: Beyond the “Wrong Tube”
Historically, veterinary medicine has primarily approached respiratory and gastrointestinal clinical signs as independent problems. However, given the shared anatomy of the upper respiratory tract and gastrointestinal tract, it is impossible to separate these disorders.
Can Diet Help Manage Aerodigestive Disorders in Dogs?
Historically, veterinary medicine has primarily approached respiratory and gastrointestinal clinical signs as independent problems. However, given the shared anatomy of the upper respiratory tract and gastrointestinal tract, it is impossible to separate these disorders.
These two regions include the upper airways (pharynx, nasopharynx, larynx), lower airways, pulmonary parenchyma, esophagus, and stomach. Aerodigestive disorders represent a wide range of conditions localized to shared anatomic regions for swallowing and breathing. They often reflect failures of airway protection, allowing for the entrance of food, water, and salivary secretions directly into the respiratory tract.
Recent publications have highlighted the link between respiratory signs—primarily cough—and gastrointestinal diseases. In one study of dogs presenting exclusively for cough and no gastrointestinal signs, at least one abnormality in swallowing was found via videofluoroscopic swallow study in 81% of dogs, with some of those dogs having normal thoracic radiographs. Some signs of aerodigestive problems include:
- Cough is an airway protective mechanism that can be associated with primary or secondary respiratory disorders.
- Gagging or increased effort when swallowing could localize the problem to the pharynx.
- Neck extension, repeated lip licking, and repetitive dry swallowing can be associated with gastroesophageal reflux.
- Reverse sneezing can be observed with nasopharyngeal reflux, pharyngeal collapse, or gastroesophageal reflux.
- Respiratory distress can occur after severe/acute aspiration events or acute upper airway obstruction episodes.
- Vomiting, regurgitation, stertor, stridor, and throat clearing are common presenting complaints.
Specific Aerodigestive Disorders
In order to determine the link between a patient’s diet and an aerodigestive disorder, we first need to recognize the problem. Let’s take a look at some of the specific aerodigestive disorders that are recognized in dogs.
Aspiration pneumonia
is caused by inhalation of foreign material, including saliva, gastric contents, food, and liquids into the lungs, resulting in a secondary bacterial infection.
Aspiration pneumonitis
results from inhalation of foreign material such as saliva, gastric contents, food, and liquids into the lungs, resulting in a severe inflammatory response but not associated with infection.
Brachycephalic obstructive airway syndrome (BOAS)
Abnormalities in dogs with BOAS include stenotic nares, a long soft palate, laryngeal collapse, macroglossia, abnormal nasal turbinates, and a narrow trachea.
Dental disease
Patients with severe dental disease can experience dysphagia due to pain and inadequate coordination of movements associated with swallowing.
Gastroesophageal reflux disease (GERD)
A condition where stomach contents pass backward into the esophagus. High acid and digestive contents can damage the esophagus, leading to clinical signs (GERD). If reflux extends further backward, it can cause extra-esophageal reflux (EERD) affecting the throat, nasal passages, or airways/lungs.
Laryngeal collapse
A secondary change due to progressive BOAS. Dogs with BOAS experience increased upper airway resistance, leading to negative pressure within the larynx, resulting in cartilage weakening and deformation.
Laryngeal paralysis
is the failure of the laryngeal musculature to properly move the arytenoid cartilages. This can lead to signs of upper respiratory obstruction and aspiration of food and liquids. Laryngeal paralysis can be inherited or acquired.
Lower esophageal sphincter achalasia/dyssynchrony
is a functional obstruction of the lower esophageal sphincter (LES) causing megaesophagus. The sphincter fails to open (achalasia) or opens at inappropriate times (dyssynchrony) during swallowing.
Megaesophagus
is a disorder of the muscular esophagus, resulting in dilation and poor movement of food into the stomach. Frequent regurgitation and weight loss occur.
Nasopharyngeal reflux
is characterized by retrograde movement of food from the oropharynx into the nasopharynx.
Pharyngeal weakness
is indicated by the absence of robust pharyngeal contraction, leading to inefficient bolus movement into the esophagus. This is often observed with nasopharyngeal reflux and macroaspiration of kibble.
Sliding hiatal hernia
occurs when part of the stomach periodically moves into the chest cavity. Patients with hiatal hernias are prone to regurgitation, gastroesophageal reflux, esophagitis, and complications such as upper and lower airway inflammation and aspiration pneumonia.
Upper esophageal sphincter achalasia/dyssynchrony
is the failure of the upper esophageal sphincter (UES) to relax (achalasia) or adequately relax in response to food in the oropharynx (dyssynchrony). This can manifest as difficulty swallowing, gagging, increased salivation, and hard swallowing. Reflux into the nasopharynx may lead to aspiration into the trachea.
Making the Diagnosis
Diagnostic approaches for patients with respiratory or gastrointestinal signs vary depending on the presentation. In addition to obtaining a thorough history and performing a comprehensive physical exam, the following steps are essential for accurate diagnosis.
Oral Exam
An oral examination is essential to rule out dental disease, which can contribute to dysphagia and other symptoms.
6-Minute Walk Test
This simple test evaluates a patient’s ability to oxygenate and thermoregulate after six minutes of brisk walking. It provides insights into overall respiratory function.
Thoracic Radiographs
Radiographs may be recommended in dogs with clinical signs suggestive of aspiration. They help assess lung health and identify abnormalities.
Videofluoroscopic Swallow Study
During this test, patients are offered three consistencies of food (liquid, slurry, and kibble) while eating in a natural position (free-standing). It assesses swallowing function and detects any abnormalities.
Echocardiogram
A brief or complete echocardiogram can screen for pulmonary hypertension, especially in dogs exhibiting clinical signs associated with obstructive sleep apnea.
Nutritional History is Essential
The aforementioned tests have proven to be crucial in the management of aerodigestive disorders. However, the information gathered from them is not useful unless it is interpreted in the context of the patient’s nutrition. Understanding a pet’s nutritional history is crucial for managing aerodigestive disorders. Let’s break down the questions and considerations related to nutrition:
- What does the pet eat? Include brand, flavor, and consistency. It’s essential to positively identify the food bag.
- How much does the pet eat? Specify whether it’s a measuring cup or a different unit (e.g., 7-Eleven cup).
- How long has the pet been eating the current diet?
- Is there a particular reason the pet is fed the current diet?
- Diet history: What other foods have been fed in the past? Include brand, flavor, and consistency. Why was the diet changed? Were clinical signs better, worse, or unchanged when the diet was changed?
- If the patient eats more than one kind of food consistency or different recipes: What is the proportion of the diets? Is there one consistency that appears more problematic (e.g., difficulty swallowing kibble vs. drinking water or eating canned food)?
- How often does the pet eat?
- Does the pet receive any treats? Specify the consistency of those treats (soft, chewable, hard). How often does your pet receive treats, and how many per day?
- Does the pet experience any of the following during eating or drinking?
- Coughing, gagging, throat clearing
- Flatulence or burping (especially in association with eating)
- Being a “fast” eater
- Do you have any videos of concerning behaviors?
Once we have this data, we can focus on deciphering the macronutrient profile of the pet’s diet, particularly the fat content. The Association of American Feed Control Officials’ (AAFCO) pet food regulations dictate that commercially available foods must list a guaranteed analysis (GA). While pet food labels provide a GA, it’s essential to understand that “crude” nutrients include both digestible and indigestible components. For example, the minimum crude protein listed may not represent fully digestible protein. Similarly, crude fat is listed as a minimum, but actual fat content may be higher.
This can be very misleading and confusing for owners. To determine a more accurate contribution of protein, fat, and carbohydrates, consider using metabolizable energy (ME). ME reflects the net energy available after digestion and absorption. Online calculators, such as the one on BalanceIt.com, can help calculate ME. The GA converter is one of several tools provided by this company which was originally created by a board-certified veterinary nutritionist.
How Does This Information Help Us Treat Aerodigestive Disorders?
After gaining an understanding of the patient’s diet and asking the right questions, we can then determine a course of action. Let’s delve into how this information helps shape the treatment plan for aerodigestive conditions:
Determining Fat Content (ME%)
For patients with gastroesophageal reflux, calculating the percentage of fat in their diet is essential. These patients benefit from smaller, more frequent meals with lower fat content. This approach promotes stomach emptying, reducing the pressure that can induce reflux or herniation.
Additionally, addressing obesity is crucial. Obesity affects various body systems, including the respiratory tract. Calculating a patient’s daily nutritional requirements for weight loss is an important aspect of management.
Identifying Problematic Diets
Understanding if one diet appears more problematic than others can guide treatment trials. For instance, if a pet coughs with water, eliminating liquid water may be attempted. Strategies include soaking and mashing kibble, feeding canned diets, or using water thickeners.
Managing Megaesophagus
Changes in diet consistency play a significant role. Patients with megaesophagus benefit from a moderate-fat, calorically dense diet. This allows them to obtain necessary calories while eating a smaller volume of food.
Nasopharyngeal Reflux and Laryngeal Paralysis
Patients with nasopharyngeal reflux and laryngeal paralysis benefit from avoiding kibble. Feeding canned diets or soaked and mashed kibble can be helpful.
These examples highlight how understanding nutrition and asking targeted questions can impact aerodigestive disorder management. Sometimes dietary changes alone suffice, while other cases require a multifaceted approach alongside addressing underlying conditions. In situations where advanced diagnostics (e.g., videofluoroscopic swallow study) are unavailable, attempting these trials sequentially is reasonable.
Key Points in This Article
- Consider aerodigestive disorders in dogs with cough, regurgitation, or recurrent aspiration pneumonia.
- Obtain a thorough dietary history to identify potential aerodigestive issues.
- Diet modifications can significantly impact patient outcomes, either as a sole intervention or in conjunction with other treatments.
- An oral examination is essential to rule out dental disease, which can contribute to dysphagia and other symptoms.
- Understanding a pet’s nutritional history is crucial for managing aerodigestive disorders.
Photo credits: Liudmila Chernetska/iStock via Getty Images Plus with Adobe generative AI, Yana Tikhonova, BWFolsom/iStock via Getty Images Plus