1. Initiation of exercise
- The abrupt increase in ventilation at the start of exercise is due to neural changes that send excitatory impulses to the inspiratory area in the medulla oblongata.
2. Moderate exercise
- The increase in ventilation during moderate exercise is due to chemical and physical changes in the bloodstream, including slightly decreased PO2, slightly increased PCO2, and increased temperature.
3. Asthma attack
- The walls inside the airways in the lungs becomes inflamed and swollen if you have asthma, making it narrow. The membranes in the airway linings also secrete excess mucus.
4. Abrupt ascent into high altitudes
- The amount of oxygen in the air goes down as you climb higher above sea level. The reduced oxygen content in the blood induces breathing instability.
5. Pneumonia
- The infection can cause the air sacs in the lungs to become inflamed and filled with fluid or pus. As a result, it becomes difficult for oxygen to enter the bloodstream.
6. Paralysis of phrenic nerve
- The phrenic nerve causes the diaphragm to contract and expand, giving the lungs ability to inhale and exhale air. Damage in the phrenic nerve can cause the diaphragm to be paralyzed.
7. Severe tuberculosis with resulting lung scar tissue
- Tuberculosis affects the lungs. Once the bacteria are inside the lungs, they multiply and cause inflammation.
8. Severe anemia
- A person with anemia has less oxygen in their blood. The lack of oxygen in their body makes them feel breathless.
9. Advanced COPD (chronic obstructive pulmonary disease)
- The obstruction or collapse of airways causes the airway resistance to increase.
10. Advanced pregnancy
- Contraction of the diaphragm is responsible for about 75% of the air that enters the lungs during quiet breathing. Advanced pregnancy can prevent complete descent of the diaphragm.