Heavier breathing in dogs could be an airway disease
By Bruno Massat, DVM, DACVS, DECVS, CCRP
Friday, June 12, 2009
Published in the "Your Pet" column of The Nashua Telegraph.
The column runs on the second and fourth Fridays of each month.
Once the snow melted, it was time to take Roxy for a long-overdue hike.
Roxy, an 8-year-old Labrador retriever, is more than happy to oblige; he is still going strong and loves to run in the forest. He never had any serious disease his entire live.
But more recently, his breathing had become a little noisy. Not that Roxy cares; it does not impair him to be his happy and bouncy usual self. Midway through the hike, his owner finds Roxy on his side, his hanging tongue turned blue, saliva pouring from his mouth and suffocating. Meet laryngeal paralysis, the most common airway disease in large dogs.
The larynx is a complex structure, shaped as a box of several articulated cartilages, muscles, vessels and nerves. It is the gatekeeper to the windpipe. It closes during swallowing, guiding food toward the stomach and not the lungs. Otherwise, it is largely open to allow rapid flow of air into the lungs during inspiration, and it relaxes during expiration. The larynx also is the site of the vocal cords and the origin of barking.
In normal dogs, this fine mechanism is coordinated by the laryngeal nerves. When LP develops, the larynx is unable to open normally during inspiration. The air has to work its way through a small fissure. During exercises, as the demand for oxygen and the respiratory rate increase, the turbulent air flow creates inflammation and swelling of the mucosa, decreasing the size of the laryngeal opening even more; oxygen supply becomes compromised; and the dog asphyxiates and collapses.
From this point, two possibilities exist. The favorable one, with the dog now quiet, is that respiration normalizes and the dog recovers, until the next episode. The worse outcome is sustained asphyxia, high body temperature (indeed, dogs maintain their temperature mainly by panting), irreversible damages to several organs and death.
The warning signs of LP are mild and insidious. Breathing becomes noisy, intermittently at first, then more consistently. Voice changes develop with a progressively duller and muted bark. In advanced cases, the dog has permanent raspy breathing and becomes sedentary; even the quiet daily leash walks can become problematic. LP appears seasonally; in warm temperatures, dogs pant more, aggravating the symptoms. Coughing and labored breathing could be the sign of aspiration pneumonia, an infection of the lungs by aspirated food particles. Pneumonia is a serious disease on its own, which requires medical treatment with antibiotics and even hospitalization. If difficulty swallowing and overall weakness are also present, LP could be a symptom of a more generalized muscular or nervous disease. In rare cases, LP could also be associated with a deficient thyroid.
As always, prevention is better than treatment. Very simple measures are effective in preventing asphyxia and collapsing episodes. If you suspect that your dog has LP, make sure she or he remains inside with the air conditioning on during the warm summer days. Plan outside activities based on weather. Use a harness instead of a collar. Limit exercise as dictated by the dog tolerance. A mild tranquilizer may be indicated in stressful times.
If you are confronted with an episode of severe difficulty breathing or a collapse, keep your dog quiet, cool him down with a fan or ice packs placed on the paws, and contact your veterinarian immediately. With emergency treatment, the patient will likely survive. Once stable, with a confirmed diagnosis of LP, surgical treatment can be provided.
The surgery is called a laryngoplasty. The surgeon reaches the larynx from the left side of the throat. Two of the laryngeal cartilages are disarticulated and sutured together in an open position. The result is a laryngeal opening permanently enlarged on one side, allowing for comfortable breathing. Most dogs return to a moderately active lifestyle.
But there are two small prices to pay for this privilege. The first one is barking, which becomes even more muted after the procedure. The second is a slightly increased risk of aspiration pneumonia; precautions during meals are needed (elevated feeding, smaller and more frequents meals, no stress at meal time). But as any asthma patient would tell you, the feeling of suffocating is one of the worst in the world, and it is worth the trade. For regular cases of LP, the prognosis for a good quality life after a successful surgery is excellent. Unfortunately, when LP is secondary to a generalized disorder, the surgery may be contra-indicated and the prognosis for long-term survival is more guarded.
So, what about Roxy, you wonder? He survived the episode, and I never saw him again after his surgical follow-up. But you should have seen Roxy's owner the day he carried his dear friend through the woods on this hot summer day. He is the true survivor!
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