Briefly explain the main cause or mechanism of increase in respiratory rate or depth and/or respiratory difficulties in the following cases:
1. Initiation of Exercise
When a person starts doing exercise, his muscle works harder and requires more energy, thus needing more supply of oxygen. For this oxygen supply to the lungs, the respiratory rate and depth rises, allowing for more oxygen to be absorbed and carbon dioxide to be expelled.
2. Moderate Exercise
The reason for increase in respiratory rate at moderate exercise is almost similar with the initiation of exercise. The body requires more oxygen to be supplied as it uses more enrgy, thus the breathing increases. The respiratory rate and depth rises, allowing for more oxygen to be absorbed and carbon dioxide to be expelled.
3. Abrupt Ascent into High Altitudes
Partial pressure decreases at high altitude, causing the decrease in the amount of oxygen, which makes our body exposed to lower oxygen pressure in an abrupt ascent to high altitudes. Due to this, the respiratory rate rises to compensate for the reduced oxygen availability, allowing for more oxygen to be absorbed in this condition.
4. Paralysis of Phrenic Nerve
The phrenic nerve provides the primary motor supply to the diaphragm, thus, paralysis of phrenic nerve may cause diaphragm dysfunction leading to shortness of breath and reduction in blood oxygen levels. Some patients experiencing this case may need a mechanical ventilator to breathe when their (high) respiratory rate alone is not able to maintain adequate oxygen levels.
5. Severe Anemia
Anemia causes low levels of hemoglobin, preventing the blood to carry an adequate amount of oxygen to reach the brain, thus the difficulty in breathing. Anaemia is increasingly recognized as an important comorbidity in the context of chronic obstructive pulmonary disease, and the lungs need to overcompensate (increase in respiratory rate) in order to bring in more oxygen.
6. Advanced pregnancy
Rising progesterone levels in pregnant women stimulate respiration, and the push of abdominal organs up against the diaphragm causes pressure thus the shortness of breath. With this, the lower lung capacity increases to meet the body’s oxygen demands.
References:
Your lungs and exercise. (2016). Breathe, 12(1), 97–100. https://doi.org/10.1183/20734735.elf121
San, T., Polat, Ş., Cingi, C., Eskıızmır, G., Oğhan, F., & Çakır, B. Ö. (2013). Effects of high altitude on sleep and respiratory system and theirs adaptations. The Scientific World Journal, 2013, 1–7. https://doi.org/10.1155/2013/241569
Mandoorah, S. (2023, August 8). Phrenic nerve injury. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books
Guo, J., Zhou, C., Xiao, Q., Gong, S. S., Zhao, Q., Wang, L., He, J., Yang, W., Shi, X., Sun, X., & Liu, J. (2015). Impact of anaemia on lung function and exercise capacity in patients with stable severe chronic obstructive pulmonary disease. BMJ Open, 5(10), e008295.
LoMauro, A., & Aliverti, A. (2015). Respiratory physiology of pregnancy. Breathe, 11(4), 297–301. https://doi.org/10.1183/20734735.008615