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 - Initiating exercise makes muscles work harder, thus the body produces more carbon dioxide that stimulates increased respiration. This is due to the neural changes that send excitatory impulses to the inspiratory area in the medulla oblongata.
2. Moderate exercise - Due to an increase in the depth of ventilation rather than increased breathing rate. To cope with extra demands, respiratory rate increases.
3. Asthma attack - The respiratory difficulties experienced during an asthma attack are due to chronic airway inflammation and hypersensitivity, muscle spasms in the walls of bronchioles, and excessive mucus secretion which blocks smaller airways. The narrowed airways cause air to be trapped inside the lungs – making it harder to breathe.
4. Abrupt ascent into high altitudes - Mostly due to the changes or reduced oxygen levels that induce respiratory difficulties or high-altitudes periodic breathing (PB). The lungs respond with hyperventilation which aims to supply the body with enough oxygen.
5. Pneumonia - Due to an infection in the alveoli which causes inflammation and fluid/pus buildup which contributes to breathing difficulties. Shallow breathing results in increased respiratory rate.
6. Paralysis of phrenic nerve - Since it is critical in the contraction and relaxation of the diaphragm, paralysis of the phrenic nerve leads to paralysis of diaphragm. This leads to difficulty in maintaining adequate gas exchange because of the inability and insufficiency of the lungs to inhale and exhale.
7. Severe tuberculosis with resulting lung scar tissue - Due to Mycobacterium tuberculosis that multiply and cause inflammation to the lungs and the pleura. This drives airway obstruction thus respiratory difficulties
8. Severe anemia - Anemia, a known cause of respiratory distress, makes the lungs overcompensate in order to supply more oxygen to the body.
9. Advanced COPD (chronic obstructive pulmonary disease) - Due to airway blockage or the inability of the airways and air sacs in the lungs to stretch and shrink back. This causes airflow obstruction which leads to respiratory difficulties.
10. Advanced pregnancy - Due to increased progesterone, a pregnant woman breathes more deeply to meet the oxygen demands of the fetus. Advanced pregnancy also prevents the complete descent of the diaphragm.