Pugs Breathe and Burn Too Brightly
…and their form follows their function
Pugs are adored for their big eyes and snuffly faces. But those same features are signs of a body locked into overdrive. They don’t just snore — they hyperventilate. And that baseline of fast, shallow breathing reshapes their entire physiology.
Breathing Too Fast
At rest, a pug’s breath rate runs high. Every quick breath blows off carbon dioxide — the very gas that helps stabilize blood chemistry and calm the nervous system. Low CO₂ means smooth muscles tighten, blood vessels constrict, and the whole system tips toward sympathetic “fight or flight.”
The Barrel Chest
When CO₂ is lost, muscles everywhere tighten. The diaphragm stiffens, and so do the smooth muscles in the walls of the airway tubes. These tubes taper twice — once through the nose, and again just before they reach the alveoli. Tightened walls at either end make flow harder. In the nose, narrowing pushes the animal toward mouth-breathing. In the distal branches, it makes drawing air in a struggle. The chest wall adapts by building strength: intercostal muscles harden to haul air down. But strength doesn’t solve the other half of the cycle. On the way out, the narrowed distal walls collapse. Air is trapped. Alveoli over-inflate. The chest rounds into a barrel.
The Bulging Eyes — Skull, Thyroid, and Stress
The pug’s eyes bulge for more than one reason. Part of it is mechanical: a shortened cranium and shallow bony orbit leave little room, so the eyes are physically pushed outward. Part of it is physiological: constant air hunger and low CO₂ drive the system into sympathetic overdrive, a state that in humans often tips the thyroid into hyperactivity — with the same wide-eyed stare.
Breath is the messenger. Stress is relayed into the body by the rate and depth of breathing. Fragmented sleep blunts growth hormone release, leaving limbs foreshortened and repair incomplete. The body keeps burning, but it cannot rebuild.
Genetics and Epigenetics
This is not simply genetics. Breeding two pugs means drawing again and again from a narrow genetic pool — so the same structural constraints are repeated. But on top of that, the way the animal breathes acts as an epigenetic force. Over-breathing doesn’t just stress the system in life; it shapes growth, form, and function across generations.
A Thyroid in Overdrive
The thyroid gland is exquisitely sensitive to oxygen and carbon dioxide balance. When breathing runs fast and CO₂ stays low, metabolism tips into a higher gear. Just as in humans under chronic stress, the thyroid can be pushed into a hyperactive state. The result is a body that burns too brightly: heart rate always high, heat production cranked up, tissues racing through energy.
About the Author:
Catherine Broué is a systems physiologist. After two decades in ICU and dialysis, she turned to the deeper question of real health, guided by mentors and the insights of Bohr and Buteyko. Her work centres on the body’s true regulators — breath and the central nervous system — and the return to parasympathetic dominance
Human Echoes — The Thyroid in Overdrive
I once had a dialysis patient who insisted on finishing every treatment “dry” — being about a litre under a decent which would actually match her body weight. Each time she came off, her heart was racing and her breathing was rapid and shallow. She lived in sympathetic overdrive, and eventually her thyroid followed suit: she developed hyperthyroidism.
The science backs this pattern. Case–control studies and meta-analyses show that stressful life events and chronic physiological stressors often precede the onset of Graves’ disease, the most common cause of hyperthyroidism. Stress is carried into the body through breath rate and depth seems to be one of the key messengers — tightening smooth muscle, altering circulation, and ultimately tipping endocrine glands into overdrive. In some patients, the wide-eyed stare of exophthalmos is as much a sign of chronic air hunger as it is of glandular disease.
More Than One Diagnosis
If pugs were people, they would carry multiple labels:
COPD, for their hyperinflated lungs and barrel chests.
Asthma, for their reactive small airways that clamp down under stress.
Sleep apnoea, for their collapsing upper airway at night — the kind of problem that earns a CPAP machine in humans.
Hyperthyroidism, for their constant metabolic overdrive, a glandular reflection of their relentless breath.
Dry Air, Wasted Effort
Here’s the paradox: oxygen can only enter the bloodstream when it dissolves in the thin layer of fluid lining the alveoli. Dry air — like the unconditioned air pulled in through the mouth — dehydrates those surfaces. That means oxygen uptake is poor even as carbon dioxide continues to be blown off. The body breathes harder but feeds less. It is not really breathing, only blowing.
Form Follows Function
What looks like “just the breed” is physiology written into flesh. Stress and overdrive carried by the breath rate and depth sculpt the body over time. For pugs, that means a shorter life span, a chest that balloons, eyes that bulge, limbs that stay foreshortened, and a thyroid that runs hot. Even their cuteness is the mark of their disease.
