Equine Upper Airway Noise: What Does it Mean?

A guide to your horse’s roaring and whistling, gurgling and fluttering

He’s a head-turner all right. Every time he laps the arena, he captures the attention of anyone around—or, more precisely, anyone within earshot.

Horses that roar, whistle, gurgle, or make any other kind of repetitive and seemingly involuntary noise from the nose and throat grab attention, and not in a good way. Those sounds aren’t just distracting or annoying; they can also spell trouble. Noisy breathing often means compromised breathing, due to a blockage in the upper airways that inhibits proper airflow.

Though it can, rarely, resolve on its own, airway noise always merits investigation, our sources say. Without treatment, affected horses will likely face ongoing—and in some cases progressively worsening—health and performance constraints.

The Anatomy of the Equine Airways

When a horse breathes, air passes through the nostrils into the long nasal cavity to the nasopharynx. Then it passes over the epiglottis, through the larynx, and into the trachea, where it descends into the lower respiratory system for gas exchange.

A horse’s nasal cavity is large compared to that of other domestic animals, to take in high volumes of air, says Laurent L. Couëtil, DVM, PhD, Dipl. ACVIM, professor in the Department of Veterinary Clinical Sciences and director of Equine Research Programs and the Equine Sports Medicine Center at Purdue University, in West Lafayette, Indiana.

The nasopharynx isn’t a tissue structure but, rather, a passageway formed by muscles and other structures. A soft tissue structure known as the soft palate separates the nasopharynx from a similar passage in the mouth (the oropharynx). In humans the soft palate opens at the back of the throat, allowing air to pass from the mouth to the nose and vice versa. But in horses the soft palate extends so far back the throat is essentially closed off—forcing horses to breathe through their nostrils only, regardless of the intensity of physical exertion, Couëtil says.

That area of the throat is nonetheless a crossroads—primarily serving the gastrointestinal system. Lying at the back of the soft palate is the epiglottis, which covers the descending airway passages to block food from entering, Couëtil explains. The esophagus lies above those airway structures. So, essentially, the epiglottis acts as a sort of drawbridge, opening during breathing and closing during swallowing, he says, so food can reach the esophagus on its journey to the stomach.

Once the air passes the epiglottis, it goes through the tunnel of the larynx—known as the voice box because it contains the vocal cords. After the air exits the larynx, it heads through the trachea, which is the nearly 3-foot-long flexible, cartilage-lined “pipe” that delivers gases down to the lungs’ bronchi (airways) and alveoli (air sacs at the airways’ end).

In this lower part of the respiratory system, inhaled oxygen enters the horse’s circulation and gets replaced by carbon dioxide—the “waste gas” the bloodstream delivers to the alveoli and bronchi. That carbon dioxide then follows the same airway path in reverse—up the trachea to the larynx, over the epiglottis, across the soft palate into the nasopharynx, and through the large nasal cavities, where it gets exhaled through wide nostrils.

Upper Airways: Cleaning and Heating Units

Outside air is too cool, dry, and impure for the body’s delicate internal systems. Fortunately, the upper airways serve as organic air-conditioners, filtering, humidifying, and warming the air, says Couëtil.

This incredibly efficient system takes in ambient air and heats it to body temperature in a single breath, he says. It also saturates the incoming air with water vapor, which helps prevent lung irritation. Along the passageways, the various structures filter out floating foreign particles, such as dust, from largest to smallest. Hair and mucus in the nasal cavities catch the bits exceeding 100 microns in diameter.

“Anything bigger than a cross section of human hair gets stuck in the nose,” Couëtil says. More filtering occurs through each upper airway structure until nothing larger than 5 microns (invisible to the naked eye) can enter the bronchi.

The Top 3 Noise-Making Pathologies

Not all respiratory noises are bad. Some, such as clearing the nose or heavy breathing from intense exercise, are normal. But many noises do reflect pathologies (diseases or damage) that affect health and performance, says Eric Parente, DVM, Dipl. ACVS, professor of surgery at the University of Pennsylvania School of Veterinary Medicine, in Kennett Square.

If you can hear a horse’s respiratory noise from any distance, it’s probably coming from the upper respiratory tract, says Couëtil. “You have to have your ear up to the horse’s nose or even use a stethoscope at the horse’s chest to hear wheezing from asthma or any other lower airway sounds,” he says.

Equine Upper Airway Noise: What Does it Mean?

At least a dozen upper airway pathologies can cause respiratory noise, says Parente. In fact, it’s not uncommon to see a combination of conditions at play. However, three stand out as being the most common: 

1. Laryngeal hemiplegia, resulting from laryngeal neuropathy (“roaring”)

As with our head-turner at the beginning of the article, one side of the horse’s larynx, usually the left side, becomes weak due to nerve damage, which can occur spontaneously or as a result of an injury. Over time, the weakness can turn into full paralysis, preventing that side of the larynx from opening as air flows through. It results in a narrowing of the passage through the larynx and causes rattling of the weak laryngeal tissues, creating the “roaring” noise.

“Essentially, it’s a restrictive noise heard on inspiration (inhaling) with every breath, and it gets increasingly louder as the horse exercises harder and also as the disease progresses,” Parente says. The noise can vary from horse to horse, sounding like anything from a whistle to a full lion’s roar.

Laryngeal hemiplegia won’t improve on its own and worsens gradually over time, Parente and Couëtil say.

2. Dorsal displacement of the soft palate (DDSP)

Although the soft palate extends all the way back to the epiglottis, it’s not connected to it. A healthy soft palate lies slightly underneath the epiglottis, permitting the air to flow freely between the nasopharynx and the larynx and vice versa. But with DDSP the soft palate moves slightly above the epiglottis, blocking airflow as the horse breathes out. “A fluttering, gurgling noise on expiration (exhaling) is usually consistent with DDSP,” Parente says.

Sometimes people refer to this condition as “swallowing the tongue” or “choking up,” though neither is ­accurate.

Unlike roaring, DDSP sounds can be intermittent. “It’s not really a progressive disease, and the horse can make it stop for a while by certain movements like swallowing,” Parente says. “It all depends on what the horse does with his throat, essentially.”

Because it’s an expiratory obstruction, blocking outgoing rather than incoming air, DDSP might seem less serious. But that’s not the case. “The volume getting breathed in and out of the lungs is limited, so if a horse can’t breathe out all the way, the next breath in is restricted, as well,” Parente says. “The inspiratory compromise can be pretty significant. Racehorses, in particular, due to the effort they put out, can really lack the amount of air they need and slow down dramatically.”

3. Epiglottic entrapment

The membranes around and/or under the epiglottis can move atop the epiglottis, causing it to malfunction. What’s more, those displaced membranes can become swollen and cause blockages, affecting both inhaling and exhaling.

Because of its proximity to the epiglottis, this pathology is often associated with DDSP. “The pathologies may occur concurrently, and that can lead to significant respiratory obstruction,” Parente says.

Epiglottic entrapment sounds “similar to other laryngeal obstructions as a restrictive noise when it is more severe,” he adds, but in most cases, it’s more likely to cause displacement (which makes its own noise) than noise.

Less Frequent Conditions

Other upper airway pathologies primarily include infections and deformations, our sources say. For example, with arytenoid chondritis/chondropathy, the arytenoids (cartilages that are part of the larynx) become infected and swell, often after the horse is exposed to certain bacteria or viruses.

Some conditions, such as medial (toward the midline of the body) deviation of the aryepiglottic folds, are dynamic, meaning they only manifest under the pressure of exercise. “These folds literally get sucked into the airway,” Parente says. The epiglottis can also get sucked into the airway in a pathology known as epiglottic retroversion. “Sometimes the whole pharynx collapses,” he adds.

Malformations can create respiratory noise, as well, he says. Abnormalities of the nasal cavities, nostrils, sinuses, or septum can cause obstructions, as can cysts that grow in various parts of the respiratory tract. Occasionally, these disorders result from injury or infection, but most of the time affected horses are born with them. They might not become obvious until the horse exercises heavily at higher levels and needs better airflow.

“You might not know about it if there’s not a big respiratory demand on the horse,” Parente says.

Getting Inside the Airways

Diagnosing the cause of respiratory noise requires imaging equipment to see inside the horse’s throat. The first step is a resting endoscopy, Parente says, in which the veterinarian inserts a small, lighted camera into the standing horse’s airways to visualize tissue function during inhalation and exhalation. Resting endoscopies can reveal most upper airway disorders, showing abnormalities such as an unresponsive side of the larynx, an out-of-place epiglottis, or a soft palate that rises during exhalation. They can also show most congenital deformities and traumatic injuries affecting airway flow.

With dynamic pathologies, our sources say it can be helpful to mimic the effects of exercise by increasing breathing pressures manually.

“You can hold up the horse’s nose and block off most of the nostril, leaving just a small slit for him to breathe through,” Couëtil says. “This makes him breathe more deeply through increased resistance, like he would during exertion, and it magnifies the abnormalities.”

If that doesn’t work, however, a dynamic endoscopy might reveal the problem. Veterinarians can perform this procedure on horses as they exercise on a treadmill. Another option is to use overground endoscopy, in which veterinarians use a mobile endoscopic system that records airway activity while horses exercise in an arena (as in the photo on page 27) or on the track.

Ultrasonography can complement endoscopy for checking the integrity of certain airway tissues, says Couëtil. However, because ultrasound is echo-based, it can’t provide images of air-filled spaces. Radiographs and computed tomography (CT) scans can help identify structural abnormalities, he adds.

Surgical Remedies

Most noise-causing upper airway abnormalities require surgery to correct, Parente says.

For roaring, surgery comes in two forms, depending on the goal, says Couëtil. “Racehorses and other horses using high levels of energy need that airway fully opened up, requiring tieback surgery, where we reposition the paralyzed side of the larynx to keep it out of the way,” he says. “But for dressage horses, for example, they can work fine with the amount of air they’re getting, and the only real problem is the noise distraction, which can also make their scores drop. So in those cases we can just remove the vocal cords, which is the part of the larynx that’s vibrating and making the noise.”

Surgeries involving the larynx, however, permanently affect the horse’s vocal capacities. “They can’t whinny the same way anymore or, if both sides of the vocal cords are removed, they can’t whinny at all,” Couëtil says.

In epiglottic entrapment and DDSP cases, as well as any other tissue displacements, the operative goal is to move the tissue back into its correct position and secure it to keep it from moving back, he and Parente say.

These “aren’t life-saving surgeries, but performance-saving surgeries,” says Parente. Owners can decide against the operation without compromising their horse’s health, but he says it might mean compromising performance.

“You can certainly retire or reduce the activity level of these horses, provided the veterinarian agrees with that decision,” he says. “If the horse has a mild abnormality and is a pleasure horse, he’s going to be just fine.”

Couëtil agrees: “If the exercise isn’t strenuous, then they’re getting enough air and aren’t feeling stress or pain.”

Medical Therapies

Some upper airway noises resolve with medical treatment alone, says Couëtil. That’s especially the case with viral, bacterial, or fungal infections that can improve with anti-inflammatories, combined with antibiotics or antifungals as necessary. “We’ll often use a topical anti-inflammatory and an antiseptic, which is essentially a throat spray,” he says.

Growing horses might avoid surgery if their airway issues are related to uneven growth, which can resolve naturally over time. “They grow fast, and the head and neck are sometimes proportionally smaller and have narrow airways for their body size,” says Couëtil. Young horses also tend to pick up viruses more frequently—“like kids with colds,” he says—which affect their airways. Conservative treatment with anti-inflammatories can help relieve both issues.

For treating DDSP conservatively, researchers have developed a special collar, Couëtil says, that looks like a cribbing strap and helps prevent displacement. It’s efficacy still needs to be evaluated, however, in naturally occurring DDSP cases.

Occasionally, upper airway issues are associated with concurrent lower airway disorders such as asthma, in which case corticosteroids and bronchodilators (medications administered via nebulizers to widen horses’ bronchi) could help, Couëtil says. However, because bronchodilators only work on smooth involuntary muscles such as those in the lungs, they won’t help open the upper airway muscles, which are voluntary.

Take-Home Message

You know when your horse’s airway noise is normal, whether he’s clearing his nose during work or exhaling powerfully with intense effort. But when a noise seems unusual or repetitive, or if your horse is struggling to perform, it’s worth getting a veterinary evaluation. Upper respiratory tract noises can indicate narrowing of the passages that limit air intake and output, compromising health and performance. By pursuing proper diagnostics, you and your veterinarian can decide which treatment options are best for your horse. If you choose not to treat, you can improve his health and welfare by reducing his work level, keeping oxygenation demands consistent with his airway’s abilities to meet them.