1. Initiation of exercise
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Initiation of exercise causes an abrupt increase in breathing followed by a more gradual increase. As the body increases activity, there is also a need for more oxygen to be absorbed.
2. Moderate exercise
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During moderate exercise, the body increases the depth of breathing, allowing more oxygen into the body per inhalation. The rate of breathing is also increased to allow a much larger amount of oxygen when needed.
3. Abrupt ascent into high altitudes
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At high altitudes, there is less oxygen present which is why during ascent, the body increases the breathing rate to absorb more oxygen at a given time.
4. Paralysis of phrenic nerve
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The phrenic nerves control the movement of the diaphragm during breathing, thus, the paralysis of this nerve would not allow or would even terminate proper breathing. Such cases can result in ventilator dependency.
5. Severe anemia
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Anemia is a condition wherein the blood lacks red blood cells–the carrier of oxygen to deliver it in different parts of the body. In this condition, despite increased breath rate, there is still shortness of breath.
10. Advanced pregnancy
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The expanding of the uterus during advanced pregnancy pushes up the diaphragm, causing less space for the lungs therefore having the need to inhale more to absorb more oxygen. Some hormones during pregnancy also trigger the need to increase respiratory depth.