If you’re breathing through your mouth, you may be sabotaging your diaphragm, your posture, and your acid-reflux/hiatal hernia barrier.

Educational content reviewed by licensed APRN medical staff. Not personal medical advice.

In the video, Dr Vikki Petersen explains what the hidden link is between mouth-breathing, diaphragm dysfunction, intra-abdominal pressure spikes, posture and reflux/hiatal hernia — plus how to fix the root cause.

Hiatal hernia is very common (≈20% general population, it increases with age).
Hiatal hernia definition: 95% are sliding, and most are small

The esophagus passes through the hiatus (opening) in the diaphragm; the crural diaphragm acts  as an external “sling” around esophagus - it acts as a valve, preventing reflux and hernia. 
When the GEJ (gastro-esophageal junction) rises above the diaphragm, two things happen: the hiatal opening widens and weakens → reflux risk increases.

The diaphragm plays an important role in the antireflux barrier (not just LES but diaphragmatic component).
Nasal breathing engages diaphragm fully (belly movement, lower ribs) vs mouth breathing which often shifting you to shallow chest/neck breathing.
This reduces diaphragmatic excursion (movement) and tone over time; diaphragm becomes less efficient and more flattened. 

Posture: mouth breathing often pulls head/neck forward (forward head posture), which changes rib cage mechanics, lengthens accessory muscles, and compromises phrenic nerve and vagus nerve -diaphragm.

Pressure dynamics: with impaired diaphragm and poor posture, the intra-abdominal pressure regulation becomes dysfunctional → more pressure spikes when coughing, lifting, straining.
Each cough, each lift, each straining episode creates an intra-abdominal pressure spike; a competent diaphragm/crural diaphragm and correct posture help buffer that.

If you're mouth-breathing, diaphragm is weak → the hiatus sees more stress → increased risk of the stomach bulging up (hiatal hernia) and reflux.

Research (study below): Diaphragmatic breathing increased LES pressure and reduced post-meal reflux events.

Mouth breathing often during sleep (snoring) means alternating cycles of airway collapse, negative intrathoracic pressure swings (rapid or exaggerated drops in pressure inside the chest – occur when someone is breathing forcefully, mouth breathing or struggling to breathe) → more reflux risk.

Root causes: nasal/sinus inflammation (allergy, mold, SIBO-driven sinusitis), autonomic imbalance (vagus suppression, sympathetic overdrive), structural airway (nasal deviation, adenoids), postural factors.
Interventions:
1. Restore nasal breathing (nasal rinse, address inflammation/allergy, ENT evaluation if structural).
2. Address systemic inflammation: food sensitivities, microbiome imbalance,
3. Postural reset: forward-head correction, rib cage alignment, diaphragm place.
4. Diaphragmatic breathing training (DBT): show technique (belly rise/inhale nose → exhale pursed lips). 

References:
Halland, M., et al. (2021). Effects of Diaphragmatic Breathing on the Pathophysiology and Treatment of Upright Gastroesophageal Reflux: A Randomized Controlled Trial. Am J Gastro, 116(1):86-94. 

Ong, A. et al. (2018). Diaphragmatic Breathing Reduces Belching and Proton Pump Inhibitor Use in Patients with Refractory Gastroesophageal Reflux Disease. Clinical Gastro and Hepat, 16(4):616-624. 

Qiu, K., et al. (2020). The Effect of Breathing Exercises on Patients With Gastroesophageal Reflux Disease: A Systematic Review and Meta-analysis. Annals of Palliative Medicine, 9(4):1524-1533. Ann of Pall Med

Niu, S., et al. (2024). Positive Effect of Deep Diaphragmatic Breathing Training on Gastroesophageal Reflux-Induced Chronic Cough: A Clinical Randomized Controlled Study. Resp Res, 25:16 9. 

Sadiq, M., & colleagues (20