PHILADELPHIA — Dogs with smushed-in noses may be adorable, but that distinctive short nose can lead to respiratory distress and disease, hospital visits and sometimes the need to receive mechanical assistance just to breathe. Fortunately, a study by researchers at the University of Pennsylvania’s School of Veterinary Medicine shows that these dogs do just as well as their longer-nosed kin during mechanical ventilation procedures.
The study was conducted by Assistant Professor Deborah C. Silverstein and graduate student Guillaume Hoareau, both in the department of Clinical Studies at Penn Vet, along with Assistant Professor Matthew Mellema of the Department of Surgical and Radiological Sciences, University of California, Davis.
Their work was published in the Journal of Veterinary Emergency and Critical Care.
Brachycephalic dogs — dogs with skulls that are shorter than they are wide — have tiny nostrils, elongated soft palates, narrow windpipes and other abnormalities of their upper respiratory tracts. This makes it difficult for them to breathe, even in ideal conditions, as anyone who has heard a bulldog snore can attest.
However, when brachycephalic dogs get lung disease, such as pneumonia, they experience a potentially deadly vicious cycle: Their increased need for oxygen causes them to breathe harder, which stresses their already weak airways, causing them to breathe even harder. With the possibility that their airways could completely collapse, veterinarians must consider whether to mechanically help such dogs breathe.
“Out of the dogs that are admitted to the ICU at Matthew J. Ryan Veterinary Hospital with respiratory disease, it’s more common for these breeds to be placed onto mechanical ventilation,” Silverstein said. “And the incidence of respiratory disease in these dogs is higher than other dogs.”
This leads to a paradox when such dogs show up in emergency rooms; they need more help breathing when under anesthesia than other dogs, but veterinarians fear they are more likely to suffer complications or may be difficult to wean from mechanical ventilators.
“It’s dogma — we know that when they’re anesthetized during an elective procedure, there’s always a chance they’re going to have a harder time waking up. Once the airway relaxes, it can easily become obstructed,” Silverstein said.
Veterinarians insert a breathing tube into a dog’s windpipe and attach it to a machine that, after monitoring the dog’s blood oxygen and carbon dioxide levels, delivers a measured amount of air with oxygen directly to its lungs. But a combination of the tube irritating the dog’s airways and the sedative drugs that are required may make it more difficult to successfully take them off of the respirator once the lung disease is less severe.
To test if this assumption was true, Silverstein and her colleagues looked at the medical records for brachycephalic dogs, specifically, French and English bulldogs, pugs and Boston terriers, that came into Penn’s veterinary hospital between 1990 and 2008. They found that brachycephalic dogs survived at the same rate as the general population of dogs.
Future studies based on this work could improve care for brachycephalic dogs by looking at a larger sample size, getting a better sense of their oxygenation levels before and during the procedure and determining whether mechanical ventilation could be avoided in favor of a more benign procedure.
As it stands now, however, the dogma about brachycephalic dogs and mechanical ventilation can be safely discarded.
“A majority of brachycephalics with respiratory issues don’t need to go on a ventilator, but, for the ones with lung disease as well, a ventilator can be very helpful in getting them through that severe period or respiratory distress,” Silverstein said. “We shouldn’t be scared to ventilate them if they need it.”