Tommy is a 9 year old, male neutered, black lab. He has been generally healthy and is only receives his monthly heartworm preventative and flea and tick treatment. He presents today in respiratory distress. This morning his owners noted that he was a bit more raspy than normal while breathing . This has been worsening for the past few months, especially with exercise or excitement. Today, about 80 degrees Fahrenheit, they were out in the warm sun working in the yard and Tommy was following them around. Shortly before presentation they noticed that Tommy was really struggling to breath and his tongue was blue and sticking out. On physical exam Tommy has tremendous inspiratory effort but expiratory effort is normal. His tongue is blue and there is foam in his mouth. He is too weak to stand. Temperature is 106 F. You cannot hear the heart over the respiratory effort and he is not moving much air. The rest of the examination is normal. See the video to see how he was breathing (this dog is not in severe distress like Tommy).
What is Tommy's problem and how do we treat?
Tommy has laryngeal paralysis (or larpar for short). When a dog or cat breaths in, muscles pull structures called the arytenoid cartilages out of the way to open the airway. The arytenoid cartilages are located in the larynx (voice box). See the diagram below. This allows air to flow freely from the mouth, into the trachea. The folds close when swallowing to prevent food or liquid from getting into the trachea and lungs.
In some dogs and cats the muscles that pull the arytenoids back become paralyzed. When this happens the arytenoids are pulled towards one another when a breath is taken in. Because of their angle, when the breath is let out, the folds naturally move away from each other. This means that a patient has difficulty bringing air into their lungs but that it is easy to let the air out.
Initially, many patients will have a harsh inspiration that really does not seem to cause them any problem. It is usually most evident when panting and excited. In some patients, this progresses to complete paralysis and they have severe, life threatening respiratory distress.
We see larpar patients have more problems in the warmer months. This is because dogs pant to cool off. When panting with larpar, the rapid movements cause the arytenoids to move together rapidly and prevent air moving into the lungs. The dog then tries to breath harder which further exacerbates the problem. This cycle can continue until the dog enters respiratory distress. At this point the patient is essentially dying due to choking/strangulation.
When a patient presents in respiratory distress due to laryngeal paralysis, they have often been struggling for some time and have swelling in the laryngeal area in addition to being severely stressed and suffering because they cannot breath. The first things we do are give them some sedative to help them relax and give oxygen. We often treat with steroids to help decrease the swelling. When they relax, the inspiratory effort decreases and they can breathe again.
This is truly a disease best managed with surgery. The surgery is called an arytenoid lateralization. The larynx is approached from the ventral surface of the neck. On one side, the attachment of the muscle that moves the arytenoid cartilage is sutured into the open position. This causes the vocal fold to be open on one side and allows the patient to breathe easily.
This procedure is not without potential complications. The biggest is aspiration pneumonia. As the vocal fold is now always open, one of the mechanisms to protect the airway has been removed. This makes it much more likely that the patient will inhale food into the lower airways (aspirate) and develop severe infection.
Tommy's owners elect to take him to surgery. Tommy responds very nicely to sedation. He relaxes, quits panicking, starts to take in more air, and gradually becomes pink again. Once he can breathe again the crisis is over, at least for the moment. Surgery is scheduled for the next day with a Board Certified Veterinary Surgeon. Tommy makes a complete recovery from his crisis and surgery. Now he needs to be monitored closely for aspiration pneumonia.
It is important to note that the other option is euthanasia. As the patient is suffering severely (not being able to breathe causes severe distress and suffering) and will die without treatment, euthanasia is appropriate. Many older animals are euthanized due to a combination of expense and a the risk of post surgical aspiration pneumonia.