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Why Is My Dog Breathing Abnormally ?

Why Is My Cat Breathing Abnormally ?

To see what normal blood and urine values are for your pet, go here

For an explanation of causes of most abnormal blood and urine tests go here

To see how tests are often grouped, go here

Ron Hines DVM PhD

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Your Pet's Respiratory Rate

Consider any extreme change in respiratory rate - up or down - as a medical emergency. Take appropriate emergency measures as you would for a human, get in the car, rush to your nearest veterinarian

Just as your dog or cat ’s body temperature and heart rate tell you a lot about its general health, your pet’s rate of breathing can alert you to potential health problems.

The rate at which our dogs and cats feel the urge to breath is controlled by several centers (respiratory centers) in their brain, working together in a complex way.

Nerves (phrenic nerves) convey those messages to muscles in the pet's diaphragm and between its ribs (intercostals muscles), establishing the respiratory rhythm. There are four of those brain centers deep within the head (in brain stem areas called the medulla oblongata and pons).

As your pet breaths normally, only inhalation requires work, exhalation is just the springy response of its elastic body. The four respiratory centers rely on chemoreceptors (cells that are sensitive to the C02 level in your pet’s blood) to establish the rate at which your pet breathes. (C02=carbon dioxide, or measured as HCO3- or bicarbonate).

Additional input in setting your pet's breathing rate comes from centers in its’s carotid arteries and aorta that measure the amount of oxygen as well as carbon dioxide in your dog or cat ’s blood stream. (ref)

At any time, your pet’s conscious brain can over ride the advice its respiratory centers give it (part of its unconscious autonomic nervous system) - at least for a while.

Difficult respiration (dyspnea) is not necessarily rapid respiration. It is generally caused by lung or windpipe (tracheal) pathology, although some of the things listed as the causes of rapid respiration can be part of the underlying problem.

Panting is not, strictly speaking, hyperventilation. It is the natural way dogs and cats cool their bodies because they do not sweat like we do (they do sweat between the bottoms of their paws). So if your dog or cat has been exercising heavily or exposed to hot temperatures, a faster respiratory rate with an open mouth (panting) is to be expected for a time. (you know your dog or cat best; any time that panting after exertion is greater than expected and without obvious cause, let your vet know.)

You know your pet has a breathing problem when it suddenly breathes differently from the way it did in the past under identical situations. Those differences might include: increased labor in obtaining sufficient air, breathing with an open mouth, increased belly and chest movement during each inspiration, louder than normal breathings sounds or wheezing, raspy or squeaky sounds, nostrils flared or elbows held wide apart, neck, head held low, and perhaps mood, anxiety, interest and appetite changes.

Reasons Why Your Pet’s Respiratory Rate Could Be High (tachypnea, hyperventilation) :

The most common reason your pet’s respirator rate might be elevated is its emotional state. Excitement, anxiety, fear, pain or even happy anticipation can all increase your pets respiratory rate (via the limbic system of its brain).

Overheating is probably the second most common cause. Pet’s are more subject to rapid breathing than we are when we are hot because their primary way of keeping their body temperature down is through panting.

The third most common cause is the increased body temperature or fever that causes increased respiratory rate. That increases your pets respiratory rate in several ways, not only because it increases body temperature.

Dehydration that accompanies heat stroke, fever or gastrointestinal problems can also cause rapid respiration as your pet’s blood volume decreases and it becomes more difficult to move oxygen around in its body.

Low blood oxygen (hypoxia) will also cause your dog or cat to breath more rapidly.
The two most common causes of low oxygen are heart failure and anemia. The most common causes of heart failure are heart valve failure in older pets and heartworms (usually in younger dogs). But any mechanical or biological reason for a heart to work less efficiently will cause the same problem.

In cats, anemia due to Feline leukemia (FLV), feline AIDS (FIV) and FIP are common causes. In both cats and dogs, sudden heart failure occasionally does occur (cardiomyopathy) and one of its signs is rapid respiration.

Another cause of anemia is autoimmune hemolytic anemia (primarily in dogs).

Any other causes I listed for low PCV and low hemoglobin in your cat or dog can also be responsible for rapid breathing. Asthma and heartworms in cats can also cause rapid, difficult breathing.

Any form of pathology in your pet’s chest cavity that prevents normal oxygen movement into the pet’s blood will also lower blood oxygen. Those could be things like fluid or loose air in the chest, lung infections, tumors or restrictions to air flow (during inspiration or expiration).

If a pet’s tummy (abdomen) swells enough, it will affect its diaphragm and through that, its ability to breath. So things like a greatly enlarged liver, fluid leakage into the abdomen or an distended (enlarged) stomach will also cause it to struggle to obtain enough oxygen. If the pet’s diaphragm was torn in a car accident or fight, it will also hyperventilate and struggle to breath (dyspnea) for the same reason.

All the causes I listed for low blood pH (metabolic acidosis) low blood pH, low blood HCO3 can also cause your dog or cat to breath faster. Problems like diabetes or kidney failure can lead to this.

Pets also breathe faster when blood bicarbonate levels are high and blood H+ levels low due to an increase in body pH (metabolic alkalosis).

Cats with an abnormally high metabolic rate due to hyperthyroidism can also breath faster than normal.

Pregnant pets sometimes breath faster because of the extra oxygen needs of their babies within them. Puppies and kittens also have a slightly more rapid respiratory rate.

Collapse of the circulatory system, as occurs in dogs and cats that are in shock due to car accidents and fights, sudden severe allergies or vaccine reactions (anaphylactic shock) or advanced heart disease will also cause them to breath rapidly - (These are medical emergencies that require the same lifesaving emergency procedures eg CPR, etc perform them as you - rush to the vet's office).

All medications that are considered stimulants in humans can be responsible for increasing the respiratory rate of your dog or cat. Some of those stimulants, like caffeine or ADHA medications, would most likely be eaten accidentally. But others, like phenylpropanolamine (Proin) , are given to control bladder leakage in older female dogs (and occasionally to cats). Too high a dose of thyroid medications (levothyroxin) can also cause increased your pet's respiratory rate.

Heart problems, such as hypertrophic cardiomyopathy (HCM), are another common cause of rapid breathing. Resting breathing rate in cats is quite variable; but normal cats take less than 30-40 breaths per minute.

Reasons Why Your Pet’s Respiratory Rate Could Be Slow (hypoventilation) :

There are considerably fewer reasons your dog or cat would breath slower than normal.

They would, of course, if they were asleep. But very rare brain diseases, affecting the pet’s respiratory centers could also be responsible. I know of none that would not cause many other more serious warnings that your pet was seriously ill.

More commonly an overdoses of all sedative medications, either those prescribed for your pet or accidentally eat cause over-sedation, coma and eventually respiratory failure – just as they would in humans. Overdoses of alcohol would do the same. In a veterinary hospital setting, amounts of general anesthetic gas or narcotics that are inappropriately large for your pet's condition or body weight will also slowly lead to total failure of its respiratory centers if not promptly tended to.

All causes of metabolic alkylosis (higher than normal blood pH levels), including serious vomiting, starvation, bicarbonate overdoses or overdoses of diuretics (furosemide) can all decrease your pet's respiratory rate. In all these cases, your pet’ blood bicarbonate level would likely be high.

Prolonged exposure to severe cold (hypothermia) also depresses your pet’s respiratory centers and rate of breathing.

Complementary Tests :

CBC/WBC and blood chemistry values including blood bicarbonate or CO2 levels. Anion gap, thoracic (chest) ultrasound and x-ray and further tests based on the results of those initial ones.

.................... DxMe