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Thursday, 20 October 2011

Difficulty breathing in dogs and cats

Welcome to PercyPods Pet Emergency blogs. This week we are going to discuss one of the most serious problems that can affect dogs and cats, namely difficulty breathing. As any of you that has had trouble breathing will know this can be very uncomfortable. It can also be life-threatening and so it is important for pet carers to be well informed about this problem.

The basics of breathing

In order to understand what can cause your pet to have trouble breathing it will be useful to briefly discuss how breathing happens and why it is important. So breathing is triggered by the brain and relies on various muscles of the chest as well as some nerves. Breathing happens in two stages. The first stage is when we breathe in, which is called inspiration. Air is sucked in through the nose but possibly also the mouth and passes the throat and vocal cords (the pharynx and larynx). It then flows down the windpipe (trachea) into the lungs.

The lungs consist of lots and lots of airways (bronchi, bronchioles) and millions of tiny little air sacs (alveoli) – you can think of these air sacs a bit like a sponge. When the air reaches these sacs, oxygen leaves the air and passes into the bloodstream. This is essential because the body needs to get enough oxygen basically to stay alive and difficulty breathing can compromise the amount of oxygen that the body receives with potentially disastrous consequences. As well as oxygen leaving the air sacs, carbon dioxide passes from the bloodstream into the air sacs. The carbon dioxide is then removed from the body as the animal breathes out; breathing out is the second stage and is referred to as expiration. Breathing out carbon dioxide is important as too much carbon dioxide is harmful for the body.

What can cause difficulty breathing?

So just to recap, breathing basically relies on the brain, some muscles and nerves, and the respiratory tract to be working well enough; the respiratory tract consists of the nose, the throat and vocal cord area, the windpipe and the lungs. An animal can therefore have trouble breathing if any one of these parts of the body has a problem. There are therefore lots of different causes of difficulty breathing and we will just mention a few of the most common ones here.

Nose, throat (pharynx) and vocal cord area (larynx)

So let’s start with the nose, throat and vocal cord areas. Problems affecting the nose usually do not cause difficulty breathing but instead may cause sneezing and discharge from the nose. However breathing can become laboured if the nose is severely blocked for example by a tumour of some sort or by severe infection; some cats with cat flu for example can develop breathing difficulty due to severe infections affecting the nose. Dogs with short-noses, such as Pugs and Bulldogs, can be affected by a condition known as Brachycephalic Airway Obstruction Syndrome. This condition includes a number of abnormalities affecting the nose and the throat areas; affected dogs may develop significant breathing problems especially on hot days, during exercise or when very stressed.

Certain dog breeds are prone to a condition known as laryngeal paralysis where the vocal cords fail to move properly which prevents them breathing in air adequately. Laryngeal paralysis typically affects large breed dogs, especially retrievers, and the problem often gets worse on hot days or during exercise. A characteristic noise can be heard when a dog with severe laryngeal paralysis breathes in. Cats can suffer for example from something called a nasopharyngeal polyp, which is basically a benign mass on a stalk that can affect the nose and throat area as well as the ear canals. They may also suffer from tumours or inflammation affecting the vocal cord area and actually tumours and inflammation of these areas are problems that can also affect dogs as well.

The windpipe (trachea)

As mentioned before, once air has passed the throat and vocal cord area it enters the windpipe or trachea. Problems affecting the windpipe are actually pretty rare as a cause of difficulty breathing. However some little dogs, such as Yorkshire terriers or Chihuahuas, can be affected by a condition known as tracheal collapse where the windpipe flattens during breathing hindering the flow of air. These dogs often have a cough that has a very characteristic sound; it is usually described as a ‘goose honk cough’ and often gets worse when the dog gets excited or stressed. Both dogs and cats can also struggle to breathe if a foreign object gets stuck in their windpipe; for example we have seen a cat with a tooth stuck in the windpipe and several dogs with little bones stuck in their windpipes.

The lungs

Finally air that is breathed in reaches the lungs. Dogs and cats can be affected by a variety of diseases and other processes that affect the lungs. Unfortunately it is quite common for cats to be hit by cars and many of these cats develop laboured breathing. In some cases this is because of air leaking from the damaged lung, a condition known as pneumothorax, with the air then collecting around and compressing the lung. This compression is a bit like squeezing a sponge so it collapses. Another common cause of difficulty breathing after a traumatic episode is bruising of the lungs; just like any other part of the body, if the lungs are injured they can become bruised and this will hinder the movement of air and removal of oxygen from the air.

Other common conditions that can affect the lungs and cause difficulty breathing include heart failure, infections in the lung causing pneumonia, and cancer. Cats can also get a condition that is similar to asthma in people and in fact it is often referred to as feline asthma or feline bronchial disease. This condition is thought to be due to an allergic problem in many cases and is especially common in certain breeds such as Siamese and Abyssinian cats. There are various worms that can also cause difficulty breathing by different means; examples are lungworm and heartworm. Some dogs in particular may also get a foreign object of some sort trapped in their lungs. The most common example of this is when dogs such as Springer spaniels who like to run in the long grass inhale a grass awn or other plant material.

And lastly we would also like to mention that there are some diseases that can affect the nerves or muscles which are involved in breathing and these can cause your pet difficulties. For example infections such as tetanus or botulism or tick bite paralysis can do this; you should note that tick bite paralysis is not found in all parts of the world.

How will I know that my pet is having difficulty breathing?

Okay so now that we have discussed some of the causes of difficulty breathing, let’s move on and talk about what signs your dog or cat may show if they are affected by one of these conditions. In many cases it will be obvious to you that your pet is struggling to breathe. You spend a lot of time with your pet and are therefore used to seeing them with normal breathing. If they are struggling to breathe, they will usually have either an increase in the rate of their breathing or an increase in the amount of effort they use to breathe; in many cases there is an increase in both rate and effort. You may notice for example that there is more movement of their chest and tummy area or that there is flaring of the nostrils.

Some of the most severely affected animals show what we call ‘postural adaptations’ – this means that they do things such as sit upright rather than lying down, stand with their elbows out, or breathe with their neck extended to help them move air. In very severe cases, you may notice that your pet’s gums take on a bluish or purplish appearance rather than their normal salmon pink colour. This is referred to as cyanosis and should prompt immediate veterinary attention.

Some animals that are affected by conditions that cause difficulty breathing may show other signs for a period of time before they really start struggling to breathe. Such signs include coughing and not coping as well with exercise, and in other cases the signs may be even more vague such as being lethargic or off their food. It goes without saying that if you are worried about your pet’s breathing you must consult your veterinary practice immediately.

What will my vet do to help my pet?

Before we finish this blog let’s discuss briefly some of the things that your vet may have to do to find out why your pet has difficulty breathing and try and treat the problem. As we have already discussed there are lots of different reasons why a dog or cat may have trouble breathing and we can only really speak in general terms here. The first thing to stress is that dogs and especially cats that are struggling to breathe are in a very vulnerable position and it is very important not to stress these animals as this can cause them to deteriorate further. So you should handle these animals gently when getting them to your vet and your vet may want to approach the management of your pet in a slow and steady fashion, taking their time to do the various necessary tests and treatments rather than risking stressing your pet. More severe cases receive oxygen therapy and sometimes various drugs to try and make them feel better and make them more stable for further tests and treatments. It may also be necessary for example to remove air or fluid from around the lungs using a needle, a procedure known as thoracocentesis.

Tests that are commonly performed in animals with difficulty breathing include ultrasonography and taking x-rays, and an ECG may be done in some cases where heart failure is suspected to see whether the heart is beating with a normal rhythm. In some cases an endoscope, which is basically like a tiny video camera, is passed into the respiratory tract under a general anaesthetic and other tests that may be performed include analysing your pet’s faeces and taking blood tests.

Depending on the diagnosis that is made your pet may need to be on medications, sometimes for the rest of his or her life, or they may need an operation. Their exercise may need to be restricted, sometimes just for a while but sometimes also more long-term. Unfortunately in some cases the cause of the difficulty breathing is one that has a very poor outlook and you and your vet may decide together that putting your pet to sleep is the kindest thing to do.

Okay so that brings us to the end of this blog on difficulty breathing in dogs and cats. It is quite a common and a serious emergency problem for which there are lots of different causes and the outlook very much depends on the cause. Your priority should be to have your pet examined by a vet and then take it from there.

The next blog will be in approximately 2 weeks time when we will talk about seizures or fits in dogs and cats. Remember that if you have any comments or questions on this blog, or indeed any suggestions for future blogs, you can contact us in the usual ways. Via email on; via the PercyPods Facebook page; or via Twitter on @PercyPods. Also don’t forget to subscribe for future episodes via the RSS feed. So thank you for reading and until next time, may you and your pets be safe.

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