Respiratory Noises in Horses

Your horse breathes noisily during exercise. Should you worry?
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Your horse breathes noisily during exercise. Should you worry?

To help you recognize serious breathing problems in horses, understand how noisy breathing will affect your horse, and learn what you can do about them, we turned to an expert: Eric Parente, DVM, assistant professor in surgery at the University of Pennsylvania's New Bolton Center, who has specialized in diagnosing and treating these equine respiratory noises.

Respiratory noises are common in horses, Dr. Parente notes, and they stem from many causes. Basically, noisy breathing can result from anything that disrupts the flow of air including sinus infections and cysts, nasal polyps, and other bulky growths that narrow the airway. In this article, we'll focus on so-called dynamic dysfunctions, glitches that keep key structures in the airway from operating as they should.? If these glitches are not fixed, often times, respiratory noises, difficulty breathing, and noisy breathing in your horse will result in more serious matters in the future.

Turbulence Ahead
The throat is the site of most of these breathing problems. It's like a highway junction where the routes that take air to the lungs and food to the stomach intersect in a common chamber, the pharynx. Several key structures here work together to ensure that food passes down your horse's esophagus to his stomach and doesn't take a wrong turn down his windpipe to his lungs which will cause difficulty breathing.

When your horse breathes in, air entering through his nostrils passes up the nasal passages and over the soft palate, a flexible flap of tissue that forms the floor of the pharynx and keeps the mouth closed off from the airway. (Unlike you, your horse can't breathe through his mouth.) The air then crosses the pharynx and enters the trachea, or windpipe, through the larynx, or voice box.

Guarding the entrance to the larynx is a valve system. Its main parts are the epiglottis, a triangular flap of tissue stiffened by cartilage, and the two arytenoid cartilages, which form an inverted V at the larynx's opening. Here's how the valve works: At rest, the epiglottis lies on the soft palate (the floor of the pharynx). But when the horse swallows, his tongue pushes back, pushing the soft palate up to block the nasal passages and forcing the epiglottis over the opening of the larynx. At the same time, the arytenoid cartilages draw together to help seal the airway. Food passes safely over the seal and into the esophagus.

The opening of the larynx also plays a role in controlling the amount of air that reaches the lungs. Along with the nasal passages, it can expand to bring in more air as the horse's need for oxygen increases, during exercise, for example. A straight path also helps the maximum amount of air reach the lungs, which is probably one reason why racehorses run with their necks stretched out.

When something goes wrong in these structures, the first sign is often (but not always) noise. Normally, air passing through the smooth, mucous-membrane-lined channels of the upper airway produces nothing louder than a soft sigh. But abnormalities create turbulence, and turbulence is noisy. If your horse develops an upper-airway problem, you may hear him . . .

The high-pitched, wheezy noise called "roaring" is by far the most common. You hear this sound when the horse breathes in, generally at the canter or gallop, when he's drawing deep breaths. The more severely the airway is obstructed, the more high-pitched and whistling the noise. In some cases the noise worsens (or appears) only when he's flexed at the poll because in that position his airway is further restricted (think of a kink in a hose).

What's happening: Roaring is characteristic of a condition called laryngeal hemiplegia, paralysis on one side of the larynx. The horse normally expands his airway to draw in more air by pulling back the two arytenoid cartilages at the opening of the larynx. In laryngeal hemiplagia, the muscle that moves one of the pair weakens, so that cartilage doesn't move or may even sag into the airway as he breathes in. With fatigue, the arytenoid flap sags in even more, so the noise becomes louder and occurs with every breath.

Roaring is most common in big, long-necked horses, and the left cartilage is the one more often affected. Why isn't certain, but nerve damage is at the root of the problem. The nerve that controls the left arytenoid flap takes a long route to its goal, and its length may contribute to its degeneration. As the nerve degenerates, the muscle atrophies, and the horse is less able to open his airway. Roaring can be mild or severe, and in many affected horses (but not all) it becomes worse over time. In a severe case, the airway may narrow to a slit during intense work.

Effects: Besides causing the characteristic noise, the restricted airflow can lead to exercise intolerance. If the horse can't deliver enough oxygen to his hardworking muscles, he tires more quickly than normal and may take longer to catch his breath after work.

This depends on two factors: the degree of paralysis (that is, how much air is cut off) and the job he's asked to do. The intensity of effort involved is at least as important as the duration: A horse asked to do hard work for a relatively short time is more likely to be limited by restricted airflow than one worked lightly but longer. Thus, a horse on the race track may be held back by even a mild case, but the same horse may do well in the show ring.

Many obvious roarers are never bothered by the condition. Roaring is seldom a significant problem for a jumper, for example, because his maximum efforts come in short bursts as he approaches and clears each jump. He has time to recover between efforts. An event horse running cross-country may be more seriously affected (especially at upper levels, where speed is a factor) because fatigue will set in; as it does, the airway will become increasingly restricted. Show hunters face a different problem: Although roaring isn't likely to affect a hunter's ability, it's considered an unsoundness.

What to do: A standing endoscopic exam can identify roaring and help determine whether it's severe enough to affect your horse's career. There are surgical fixes, but none is foolproof; before deciding on surgery, you'll want to weigh the potential benefits. If his work doesn't call for intense effort and his noisy breathing won't rule him out of the show ring, he may be able to live with the problem. Many riders find that keeping a roarer fit is helpful: Fitness delays the onset of fatigue, which makes roaring worse.

The surgery most often recommended is a tieback, or laryngoplasty. The surgeon pulls the arytenoid flap into an almost fully open position and fixes it there with a suture so it can't be sucked into the airway. After surgery, most horses get a month off and then go back to work. The down side is that the tied-back cartilage can't help close the airway when the horse swallows, so there's some risk of food and water being drawn into the windpipe. Most horses who have this surgery overcome this risk; they cough for a few days or weeks, then adjust and learn to swallow safely. In the rare case that a horse doesn't adapt, the suture has to be removed.

The surgery requires general anesthesia; although it sounds straightforward, it's technically difficult; you want to pick a surgeon who has substantial experience in doing it. Even then, the operation isn't always successful. In some cases the suture loosens, or the cartilage starts to tear loose from it, and the flap falls back into the airway; the surgeon can try again with a suture in a new spot. The alternative is to remove the weak arytenoid; however, that increases the risk of food and water going down the wrong pipe.

A horse that makes a gurgling or fluttering noise as he exhales may have a different problem: a displaced soft palate. This is less common than roaring and can be tricky to diagnose. It may pop up only during intense work or when the horse is tightly flexed at the poll. And some horses with a displaced soft palate seldom or never make the characteristic noise.

What's happening: Except when the horse is swallowing, the soft palate normally stays flat on the floor of the pharynx but in this condition, it flips up and partly blocks the nasal passages as the horse breathes out. The flapping soft palate produces the gurgle or flutter; worse, it prevents the horse from exhaling completely.

Dorsal displacement of the soft palate, as this condition is called, has no single cause. In many cases it's intermittent: The horse is galloping along just fine, and then suddenly the soft palate flops up into his airway. In some cases, however, the palate is permanently displaced.

Soft-palate problems are complex because a lot of factors contribute to them-muscle weakness, nerve damage, inflammation, abnormalities in other structures of the throat. In some cases, the epiglottis is involved: The epiglottis is anchored by a loose membrane that lets it flip up over the larynx when the horse swallows; if that membrane is too loose, it can slip over and trap the epiglottis. The epiglottis should be on top of the soft palate; entrapped, it may wind up underneath, so that the soft palate is consistently displaced.

Effects: Because the horse can't exhale properly, leftover carbon dioxide builds up in his lungs, leaving less room for oxygen when he takes his next breath. Without enough oxygen, he tires quickly and may slow and seem to struggle for air. (On the race track, this is sometimes called "choking down.") If an entrapped epiglottis is part of the problem, the horse will also have difficulty swallowing; he may inhale food and water.

What to do: Because this condition commonly appears only when the horse is working, a treadmill exam may be needed to spot it. And because many paths lead to displacement, there's no single fix. Many cases can be managed conservatively. Letting the horse travel with less flexion may be enough to prevent displacement. A common race-track solution is a tongue tie, which keeps the tongue pulled forward in the mouth so it can't push the soft palate out of position. A figure-eight noseband to keep the mouth closed can also help a great deal.

This type of throat surgery is done with the horse standing, under local anesthesia and sedation, using laser and video endoscope equipment. Laser surgery is less invasive than conventional surgery, and recovery is faster. But you'll need to travel to a university hospital or other major clinic to get it.

Maybe the sound you hear is deeper than roaring: more like heavy breathing or the intake of a snore (without the flutter on exhaling). A horse that makes this sort of deep rasp when he breathes in may be suffering from a collapsed pharynx. Intense exercise and flexion at the poll help trigger this problem, which is less common than roaring but turns up fairly regularly among horses in many disciplines.

What's happening: The pharynx isn't a rigid chamber. Its walls are soft, and it's kept open mainly by muscles. When the horse breathes in, air rushing through the pharynx pulls on the walls; if the muscles are weak, the pharynx tends to collapse inward like a wet sock. The problem shows up during hard work because the horse is breathing deeply and his throat muscles become fatigued. The stronger the pull of the air, the more likely collapse becomes. Flexion exacerbates the problem by narrowing the airway at the pharynx. Inflammation in the throat and the nerves supplying it is another factor; inflamed nerves don't fire as well, so the muscles don't contract as they should, and everything collapses.

Effects: The airway is restricted when the pharynx collapses, so the horse's oxygen intake is reduced. He tires quickly.

What to do: Because this problem shows up during exercise, a treadmill exam is the best way to catch it. Many cases respond to conservative treatment aimed at decreasing muscle fatigue and inflammation. The horse gets some time off and a course of anti-inflammatory medication, giving the injured tissues a chance to heal. Then he goes back to work gradually, in a program that slowly increases demand on the throat muscles, conditioning them the same way other muscles are conditioned. The outlook is brightest for young horses who develop this problem when they first begin strenuous work. Older horses are less likely to respond to traditional treatment and rest.

More Noises
Some other upper-respiratory conditions produce assorted gurgles, burbles, rasps, and wheezes that are easily confused with roaring (which is much more common) or the gurgle of a displaced soft palate.

What's happening: Folds of tissue on each side of the larynx may be pulled into the airway as the horse breathes in, making a sound much like roaring. Rarely, the epiglottis (which should lie on top of the soft palate except during swallowing) is sucked up into the airway. The flapping epiglottis makes a gurgling sound similar to that produced by a displaced soft palate but it occurs when the horse breathes in.

Effects: Tissue that's pulled into the airway blocks the flow of air, cutting down the horse's oxygen supply. He tires quickly.

What to do: You'll need a treadmill exam to identify these confusing "sound-alikes." Young horses who develop these problems may improve with age and a program similar to that for a collapsing pharynx -- rest, anti-inflammatories, and a slow start back into work to build strength. If folds of tissue alongside the larynx are obstructing the airway, they can be trimmed with laser surgery.

This article first appeared in the October, 2000 issue of Practical Horseman magazine.