1. Initiation of exercise
Any exercise may necessitate the mobilization and contraction of muscles that require more oxygen to contract, resulting in an increase in breathing depth and rate to promote more oxygen into the lungs and the removal of carbon dioxide from the lungs.
2. Moderate exercise
When performing moderate-level exercise, metabolic needs rise concurrently with alveolar ventilation, arterial blood-gas tensions, and acid-base balance are kept relatively near to resting values. This is because of the differences between PO2 and PCO2 in alveolar air versus pulmonary blood increase which causes the aforementioned phenomena.
3. Abrupt ascent into high altitudes
The overall atmospheric pressure falls as altitude increases, as does the partial pressure of O2. The available lung ventilation to capillary perfusion ratio is imbalanced, leading to inefficient oxygen transport into the capillary space and a reduced partial pressure of oxygen in the blood which makes it harder for a person to breathe.
4. Paralysis of phrenic nerve
Also coined as phrenic nerve palsy is when the phrenic nerve, which is the primary motor supply to the diaphragm (major respiratory muscle) is damaged. This can cause diaphragmatic paralysis and severe shortness of breath.
5. Severe anemia
Anemia is a condition in which the number of RBCs (red blood cells) is lower than normal. When hemoglobin levels drop too low, the amount of oxygen given to all tissues decreases, and other systems might attempt to restore normal oxygen levels through hyperventilation and rapid heart rate.
6. Advanced pregnancy
The expanding uterus increases end-expiratory abdominal (gastric) pressure, forcing the and decreased lung volume necessitate greater ventilation to maintain adequate oxygen levels. Additionally, progesterone levels rise, which dilates the smooth muscle of the lungs, forcing the mother to breathe in more deeply (increased respiratory depth).
Literature used:
Aliverti, A. (2016, June 1). The respiratory muscles during exercise. European Respiratory Society. https://breathe.ersjournals.com/content/12/2/165?fbclid=IwAR2HJccawOUm28Bo49GK6WCljXCsIX8mv3ItKaXYPl2e_j98TX5mHH4qB2Q
Anemia: Symptoms, signs, treatments & causes: PHLBI. Pacific Heart, Lung & Blood Institute. (2023, April 28). https://www.phlbi.org/divisions/blood-disorders/anemia/
Department of Health & Human Services. (n.d.). Pneumonia. Better Health Channel. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/pneumonia
Mandoorah, S., Mead, T. (2023). Phrenic nerve injury - statpearls - NCBI bookshelf. National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK482227/
Sharma, S., & Hashmi, M. F. (n.d.). Partial pressure of oxygen . National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK493219/
U.S. National Library of Medicine. (2016, March). Your lungs and exercise. NCBI. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4818249/#:~:text=When%20you%20exercise%20and%20your,litres%20of%20air)%20during%20exercise.