The diaphragm is the main muscle that aids breathing. During inhalation, the diaphragm contracts and moves in the inferior direction, enlarging the volume of the thoracic cavity and reducing intra-thoracic pressure (the external intercostal muscles also participate in this enlargement), forcing the lungs to expand.

In other words, the diaphragm's movement downwards creates a partial vacuum in the thoracic cavity, which forces the lungs to expand to fill the void, drawing air in the process. This partial vacuum also aids the pumping action of the heart. Chest breathing does the opposite and causes heart palpitations.

During its descent, the belly expands, the oesophageal sphincter which is at the entrance to the stomach is closed, preventing any ingress of stomach acid into the oesophagus, and the abdominal contents get the pumping action of the diaphragm to aid digestion. This pumping also allows other vital organs in the abdomen to perform optimally.

Therefore, in life the diaphragm must always descend when inhaling. This can only occur when patients' belly breathes with absolutely no visible inflation of their chest cavity!

However, patients who suffer from any symptoms of acid reflux can be observed to always chest breathe!

It is of fundamental importance that patients are taught how to correct their breathing pattern before embarking on any medications which nearly always have severe adverse effects, AND the patient may eventually fall victim to carcinoma of the oesophagus.