1. Initiation of exercise: The body prepares for an extraneous movement, therefore stimulating oxygen. It will then signal the increase of respiratory rate to react to the continuous stimulation of oxygen.
2. Moderate exercise: During moderate exercise, the rate or depth of breathing increases to produce more oxygen in the blood. It simultaneously happens with the removal of carbon dioxide in the bloodstream.
3. Asthma attack: The muscles in the bronchial tubes are inflamed and produce extra mucus that narrows the airways. With this, the airflow is limited, and difficulties in breathing are evident.
4. Abrupt ascent into high altitudes: Breathing becomes fast to supply more oxygen in the blood since there is a reduced oxygen content at high altitudes.
5. Pneumonia: The alveoli are inflamed and filled with pus, making it difficult for oxygen to enter the bloodstream.
6. Paralysis of phrenic nerve: The phrenic nerve controls the contraction and expansion of the diaphragm muscles, so it may cause shortness of breath if paralysis occurs.
7. Severe tuberculosis with resulting lung scar tissue: It destroys the alveoli's lung tissue, making it difficult to produce sufficient amounts of oxygen the body needs.
8. Severe anemia: The loss of red blood causes insufficient amounts of oxygen to be delivered to the body cells. With this, the lung overcompensates to produce more oxygen to reach the brain.
9. advanced COPD (chronic obstructive pulmonary disease): COPD patients have alterations in oxygen and carbon dioxide levels. The lung compensates for the insufficiency with a low amount of oxygen, thereby causing rapid breathing.
10. Advanced pregnancy: During this period, increased chest size is evident. There is an increase in the amount of air breathed but a decrease in the amount of air the lungs can handle.