Briefly explain the main cause or mechanism of increase in respiratory rate or depth and/or respiratory difficulties in the following cases: (one to two sentences only)
1. Initiation of exercise
When we initiate exercise, our muscles work harder than usual which causes our body to use more oxygen and produce more carbon dioxide. Since the body demands more oxygen, breathing also must increase from about 15 times a minute (resting state) to about 40-60 times a minute (during exercise).
2. Moderate exercise
Our heart rate increases in proportion to the rate of intensity of our exercise – when our heart beats more, more breathing also occurs. During moderate exercise, oxygen is used up very quickly in order to provide the muscles with energy to move, thus the heart beats faster and the breathing rate also increases.
3. Abrupt ascent into high altitudes
Our lungs must have less air pressure than the air outside our lungs in order for it to inflate because air moves from high to low pressure areas. In high altitudes there is low air pressure which makes it difficult for us to breathe; our heart also needs more blood flow to deliver the same amount of oxygen as it does at lower altitudes, thus our breathing rate and heart rate increases to bring in more oxygen into our body.
4. Paralysis of phrenic nerve
The phrenic nerve provides motor innervation to the diaphragm and respiratory muscles to allow respiration. If the phrenic nerve is paralyzed, this affects the diaphragm, which causes difficulty in breathing.
5. Severe anemia
In the case of severe anemia, there are fewer red blood cells and hemoglobin present in the body than normal which results in low oxygen in the blood. This can cause breathing difficulties because the lungs overcompensate to bring in more oxygen.
6. Advanced pregnancy
As the uterus gets bigger during advanced pregnancy, it takes up more space and pushes up into the abdomen and squeezes the lungs a little bit. This reduces the space available for oxygen exchange which causes shortness of breath.
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