Initiation of exercise - During the initiation of exercise, there is an apparent increase in breathing, and this is because of the dorsal respiratory group (DRG) that had neural changes which sent excitatory impulses (with known changes that involves anticipation of the activity, stimulation of limbic system, sensory impulses and motor impulses). Moreover, rate and depth of breathing increases even before there are changes in the PO2, PCO2 or H ion levels since the main stimulus in this immediate respiratory activity is the input from proprioceptors that stimulate the inspiratory area.
Moderate exercise - In moderate exercise, the increase in breathing is due to the increase in respiratory depth rather than the respiratory rate, this resulted from the slightly decreased PO2 due to the increase of O2 consumption; slightly increased PCO2 due to increased CO2 production (contracting muscle fibers); and increased temperature (liberation of more heat).
Abrupt ascent into high altitudes - It is known that in high altitudes, the amount of O2 decreases and this results in hypobaric hypoxia and hyperventilation. This thoroughly means that the breathing is not stable due to the increase in respiratory rate and depth in order to have more O2 in the body to adapt to being in an area that is high in altitude.
Paralysis of phrenic nerve - In this accord, one may experience difficulty in exchanging air as the diaphragm (either unilateral or bilateral) is paralyzed. Increase in respiration rate is evident as the person experiences shortness of breath due to the lost ability of being able to breathe in a normal manner.
Severe anemia - The amount of hemoglobin affects the O2 transport, and thus leads to having breathing difficulties. In order to compensate for low levels of O2, the lungs exert significant effort in bringing it to the body, increasing one’s respiratory rate.
Advanced pregnancy - During pregnancy, the growing fetus affects the upper and lower respiratory tracts and an increase in respiratory rate is evident (shortness of breath) and a decrease in respiratory depth. Furthermore, pregnancy leads to decrease of chest height (compression in the diaphragm) and there is an apparent increase of respiratory resistance (reduced lung volume and it is known that O2 is heavily vital for the mother and the fetus) .
References
Cleveland Clinic. (2022, January 9). Phrenic Nerve: Anatomy & Function. Cleveland Clinic. https://my.clevelandclinic.org/health/body/22270-phrenic-nerve
Cogo, A. (2011, February 28). The lung at high altitude. Multidisciplinary Respiratory Medicine, 6(1), 14-15. 10.1186/2049-6958-6-1-14
Iradufasha, E. (n.d.). Pulmonary changes at high altitude and altitude sickness. Osmosis. https://www.osmosis.org/learn/Pulmonary_changes_at_high_altitude_and_altitude_sickness
LoMauro, A., & Aliverti, A. (2015). Respiratory physiology of pregnancy. Breathe, 11(4), 297-301. 10.1183/20734735.008615
San, T., Polat, S., Cingi, C., Eskiizmir, G., Oghan, F., & Cakir, B. (2013, April 17). Effects of High Altitude on Sleep and Respiratory System and Theirs Adaptations. Scientific World Journal. 10.1155/2013/241569
Stanford Medicine Children's Health. (n.d.). The Lungs in Pregnancy. Stanford Medicine Children's Health. https://www.stanfordchildrens.org/en/topic/default?id=the-lungs-in-pregnancy-90-P02468
Texas Medical Institute. (2020, July 24). 10 Symptoms of Anemia You Shouldn’t Ignore. Texas Medical Institute. https://www.texasmedicalinstitute.com/10-symptoms-of-anemia-you-shouldnt-ignore/
Tortora, G. J., & Derrickson, B. (2017). Principles of Anatomy and Physiology (15th ed.). John Wiley & Sons, Inc.