When we suggest to clients that their cat should go on a ventilator, they’ll often ask, ‘Doesn’t that mean the prognosis is really bad?'” explains Tufts emergency and critical veterinarian Armelle de Laforcade, DVM. “And the truth is,” she adds, “if a cat is sick enough to be on a ventilator, she’s pretty sick. In fact, when we first got a ventilator years ago, we tended to put a cat on it right before she died as a last resort.
“So we, too, were left with the impression that it doesn’t work, doesn’t save lives. But we have found over time that if you think about the reasons to put a cat on a ventilator and you put her on early, it really is a useful tool to carry her over until she recovers from a bodily insult.”
When Do Cats Need Ventilators?
There are a number of reasons for a cat to be placed on a ventilator — a machine that breathes for her when she can’t take adequate breaths on her own. The most common example is open-chest surgery while the cat is under anesthesia. Consider the fact that cats (and people) breathe by creating a vacuum. You breathe in by contracting your diaphragm, which draws air into your chest.
The vacuum (or suction) effect is termed negative pressure. But when the chest is open during surgery, the diaphragm cannot create a vacuum, so a machine — the ventilator (also known as a respirator) — is needed to actively blow air into the lungs and expand them. It’s positive pressure ventilation rather than negative.
“Ventilation during surgery tends to be for an hour or two at a time,” says Dr. de Laforcade. The machine is called an “anesthesia ventilator” and is relatively rudimentary as ventilator machines go. It is used routinely by our anesthesia team during complicated surgeries.
“But when a critically ill cat gets put on a ventilator for a longer period of time, it’s a more sophisticated machine that can do more things,” explains Dr. de Laforcade. “You can tell the machine how many breaths to deliver per minute, how much oxygen should be in each breath, and how big each breath should be — how much pressure should be pushing air into the lungs. There are some other strategies the machine allows, too, to help the cat’s lungs participate in gas exchange. You can design the breath in a particular cat’s best interest, and when air is not being blown into the animal’s lungs, she can exhale. It’s humidified air, like the air we breathe naturally.”
The reasons for putting a cat on a sophisticated ventilator include respiratory distress from heart failure, bruising of the lungs from trauma that is significant enough to compromise their function and pneumonia severe enough that a cat needs help breathing until the antibiotics start to take effect.
“Sometimes the reason for a ventilator is neurological,” says Dr. de Laforcade. “The nerve connections are not working right, so the ribs don’t expand the chest wall. The cat needs to be ventilated until the problem is fixed or passes on its own.”
Shortness of Breath in Cats
A ventilator is often not the first tool a veterinarian will reach for when a cat comes in with difficulty breathing. “When an owner brings in a cat with shortness of breath,” Dr. de Laforcade says, “the pet goes right into a cage that has supplemental oxygen. The air we breathe is 21 percent oxygen. But if a cat can’t breathe properly and is struggling to take in oxygen, the air she’ll get in the cage will be up to 40 or 50 percent oxygen. That allows her relief.
“It’s exhausting — and scary —to have to breathe hard. The extra oxygen allows a cat to settle down, rest a little, and she can respond nicely when you start to treat whatever underlying disease you’re finding,” explains Dr. de Laforcade.
“But sometimes a cat comes in so critically short of breath — or doesn’t respond to the supplemental oxygen in the cage — that we have to do something more drastic. It’s when an animal is in severe breathing distress or continues to experience respiratory problems despite oxygen therapy that we start thinking about ventilation. We have to.” emphasizes Dr. de Laforcade. “What will happen if you leave a cat short of breath in an oxygen-rich cage is that she’ll get respiratory fatigue. She’ll become too tired trying to breathe in enough oxygen and have respiratory arrest and could die right then.”
The silver lining in switching a cat from the oxygen cage to a ventilator is that it can make it easier to figure out the cause of her respiratory distress if it’s not immediately clear. “The cage is tricky,” Dr. de Laforcade says, “because an animal struggling to breathe can’t handle much examination. She’s very stressed. You have to use a very condensed diagnostic process to get the best sense of what’s going on. But with ventilation, the animal is unconscious, so you can use the full arsenal of diagnostic tools.”
How to Hook Up Your Cat’s Ventilator
“We have to sedate the cat so we can intubate her,” Dr. de Laforcade says. “You’re passing a tube into their throat, their airway. They won’t just let you do it. Once we ‘capture’ the airway by intubation, we can give 100 percent oxygen. You can’t do that for more than a day or so. The cat will get oxygen toxicity, and her organs will start to fail. So after about the first 24 hours, we take it down to no more than 60 percent oxygen and then keep trying to dial it back. All the while the cat is hooked up to machines, unconscious on the table. She’ll have an EKG machine and a pulse ox — like the clip they put on your finger to measure your oxygen saturation except with a cat it goes on the tongue or lip.
“Once we start to see the cat’s lung function improve, we’ll dial back the amount of breaths the machine is giving along with the concentration of oxygen — let the animal do more of the work,” says Dr. de Laforcade. “Then there comes a critical time when we try to take the cat off the ventilator. We’ll start in the oxygen cage, proceeding to ambient air if we can.
“A cat on a ventilator generally has somebody sitting with her at all times — 24 hours a day,” notes Dr. de Laforcade. It can be a veterinarian or an experienced veterinary technician [nurse]. Most often it’s someone board-certified in emergency medicine and critical care. Overnight, it might be a resident who’s working toward board certification.”
That’s why many practices don’t have respirators. Usually only a large hospital will have enough trained staff to stay with a cat on a ventilator 24/7.
All that staff is part of what makes putting a cat on a ventilator expensive — up to $1,000 a day. But it truly can be life saving. “Sometimes a cat needs the support as a bridge,” comments Dr. de Laforcade. “If they’re failing respiratory-wise, the ventilator can be that bridge.”
One cat at the Tufts’s Foster Hospital for Small animals, Crazy Brodeur, developed pyrothorax — an accumulation of pus in the chest cavity due to an infection (this was after surgery) but was treated successfully with the help of a ventilator and then went home. Critical care veterinarians at Tufts have also ventilated some cats after brain surgery, who then were able to be sent on their way, too.
In other words, there are many instances in which a ventilator can save a cat’s life rather than be the last thing she experiences.
