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 - From rest, our heart and respiratory rate start to increase upon the initiation of exercise. This is caused by the stimulation of the sympathetic nervous system, where our body obtains oxygen and produces energy at a faster rate.
2. Moderate exercise - To cope with the extra demand of exercising, your breathing has to increase from about 15 times a minute (12 liters of air) when you are resting and up to about 40–60 times a minute (100 liters of air) during exercise.
3. Asthma attack - During an asthma attack the muscle wall contracts and the lining of the airways becomes swollen and inflamed. These changes cause a narrowing of the airways which is further aggravated by an increase in secretions from the mucus membrane, which may actually block the smaller airways and lead to difficulty breathing or severe shortness of breath.
4. Abrupt ascent into high altitudes - At high altitudes, barometric pressure decreases, which in turn, also decreases the pressure driving oxygen through alveoli and into circulation. This phenomena induces breathing instability, with periods of deep and rapid breathing alternating with central apnea, where people can become hypoxic.
5. Pneumonia - The infection causes the lungs' air sacs (alveoli) to become inflamed and fill up with fluid or pus. That can make it hard for the oxygen you breathe in to get into your bloodstream.
6. Paralysis of phrenic nerve - Injury to one phrenic nerve leads to paralysis of the ipsilateral diaphragm, often leading to symptoms of dyspnea. Patients with a paralyzed diaphragm have reduced breathing capabilities or are unable to control their voluntary breathing and also have difficulty maintaining adequate gas exchange, as the lungs are not able to inhale and exhale outside air as efficiently.
7. Severe tuberculosis with resulting lung scar tissue - Chest pain and shortness of breath may result from pleural effusion, which is a buildup of fluid between the thin membranes, the pleura, that cover the lungs and line the inside of the chest wall. Tuberculosis causes airway inflammation, making airways smaller and increases air velocity and displaces air to unobstructed areas, while scarring makes your lungs stiffer and less elastic so they're less able to move and take oxygen from the air you breathe.
8. Severe anemia - In anemic patients, oxygen delivery decreases and oxygen extraction is increased. With anemia, the lungs overcompensate in order to bring in more oxygen, causing breathing difficulties because of low levels of hemoglobin preventing adequate oxygen from reaching the brain.
9. Advanced COPD (chronic obstructive pulmonary disease) - With COPD, the airways in your lungs become inflamed and thicken, and the tissue where oxygen is exchanged is destroyed, so the flow of air in and out of your lungs decreases. When that happens, less oxygen gets into your body tissues, and it becomes harder to get rid of the waste gas carbon dioxide.
10. Advanced pregnancy - Respiratory resistance increases while respiratory conductance decreases during pregnancy. The diaphragm moves upward toward the chest, increase the amount of air breathed in and out, decrease the amount of air the lungs can handle, and increase oxygen usage.