- Initiation of exercise
When the body initiates an exercise, neural changes provide excitatory impulses to the dorsal respiratory group (DRG) in the medulla which then stimulates the increase in respiratory rate and depth. Examples of neural changes include stimulation of proprioceptors (ex. muscles and joints) and the motor impulses from the precentral gyrus.
- Moderate exercise
In moderate exercise, physical and chemical changes in the bloodstream primarily stimulate the increase in respiratory rate and depth. Chemical changes include an increase in PCO2 and a decrease in PO2 while physical changes include an increase in body temperature.
- Asthma attack
In an asthma attack, an asthmatic person is exposed to a triggering amount of allergens that lead to difficulty breathing. The breathing difficulty is caused by airway obstruction that results from smooth muscle spasms in the walls of bronchioles and smaller bronchi.
- Abrupt ascent into high altitudes
High altitudes have lower O2 levels compared to standard ground levels. Higher altitudes can cause hypoxic hypoxia, wherein there is low PO2 in arterial blood and tissue level which then would lead to breathing difficulties.
- Pneumonia
Pneumonia is an inflammation or infection of the alveoli most commonly caused by Streptococcus pneumoniae. The condition causes a patient to have respiratory difficulties, including dry coughs and fever.
- Paralysis of phrenic nerve
The phrenic nerve supplies the total motor innervation of the diaphragm. Its paralysis hinders the transmittance of impulses from the DRG which affects the functioning of normal quiet breathing and causes respiratory difficulties.
- Severe tuberculosis with resulting lung scar tissue
In severe tuberculosis with extensive lung scar tissue, the thin membranes and alveoli of the lungs become destroyed. This would make pulmonary ventilation and external respiration more challenging which could cause respiratory difficulties ex. shortness of breath.
- Severe anemia
In severe anemia, the lungs are put under stress as a result of overcompensation of low O2 levels in the blood. Hyperventilation, a common symptom of severe anemia, occurs when there is more forceful and frequent breathing.
- Advanced COPD (chronic obstructive pulmonary disease)
In advanced COPD, common types are emphysema and chronic bronchitis, there is increased airway resistance due to recurrent and persistent airflow obstruction. Observable symptoms include respiratory difficulties (inhalation and expiration) and wheezing (COPD - Symptoms and Causes, 2020).
- Advanced pregnancy
In advanced pregnancy, the abdominal cavity expands and the uterus presses on the diaphragm. The contact of the uterus affects the full relaxation and contraction of the diaphragm, and as a result, the mother would feel some shortness and shallow breathing (Shortness of Breath | March of Dimes, n.d.).
Note: Answers from 1-8 all came from:
Tortora, & Derrickson. (2012). Chapter 23: The Respiratory System. In Principles of anatomy and physiology (14th ed.)
Note: Answers from 9-10 came from:
Shortness of breath | March of Dimes. (n.d.). Copyright 2015 March of Dimes Foundation. All Rights Reserved. Retrieved October 27, 2022, from https://www.marchofdimes.org/complications/shortness-of-breath.aspx
COPD - Symptoms and causes. (2020, April 15). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/copd/symptoms-causes/syc-20353679