1. Initiation of exercise
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The oxygen demand of the muscles rises, and a greater amount of carbon dioxide is created as a result of the increased tissue metabolism. For more oxygen to enter and carbon dioxide to escape the lungs, alveolar ventilation increases. Muscle and joint proprioceptors trigger the dorsal respiratory group of neurons in the medulla, which regulates inspiration, hence stimulating greater ventilation.
2. Moderate exercise
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During moderate exercise, the muscles are working harder, which increases the respiratory rate and necessitates aerobic respiration. Consequently, glucose and oxygen must be provided more quickly to the muscles, and carbon dioxide must be exhaled faster.
3. Asthma attack
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The walls of the airways in the lungs swell and narrow, less air enters and exits the lungs, and mucus generated by the body obstructs the airway, making it harder to breathe.
4. Abrupt ascent into high altitudes
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There is decreased inspired oxygen, low oxygen in the alveoli, and decreased oxygen entering the capillaries. The peripheral chemoreceptors, the carotid, and the aortic bodies detect changes in the oxygen level in the blood. These receptors are sensitive to arterial oxygen until it falls below 60, resulting in hypoxia due to high altitude. Through the glossopharyngeal and vagus nerves, the respiratory system increases ventilation.
5. Pneumonia
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Due to bacteria, viruses, fungi, and parasites, the bronchioles and alveoli become inflamed. This inflammation causes the alveoli to fill with fluid, pus, or abscess, making it difficult for the body to obtain the oxygen it requires.
6. Paralysis of phrenic nerve
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The phrenic nerve contracts and expands the diaphragm, allowing the lungs to inhale and exhale air. Paralysis of the diaphragm can result from nerve injury. One may experience difficulty breathing and sleeping. A paralyzed diaphragm impairs the ability of the lungs to exchange air.
7. Severe tuberculosis with resulting lung scar tissue
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It induces airway inflammation, which leads to airway blockage, by making airways narrower, which increases air velocity and reroutes air to unencumbered locations. Thus, airway inflammation can result in the prolongation of tuberculosis infection and deposition or movement to healthy parts of the lung, which can lead to the formation of lung scar tissue over the long run.
8. Severe anemia
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In severe anemia, the hemoglobin level may drop too low, hence decreasing the amount of oxygen given to all tissues. Hypoxia, caused by low oxygen levels, generates a breathing pattern characterized by quick, shallow breaths with a proportionally greater increase in respiratory rate than tidal volume.
9. advanced COPD (chronic obstructive pulmonary disease)
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Repeated inhalation of irritants results in a chronic inflammatory which causes inflammation of the airways causes them to thicken and produce mucus, narrowing the air passage known as chronic bronchitis, inflammatory chemicals also dissolve alveolar walls, resulting in destruction of the air sacs known as emphysema.
10. Advanced pregnancy
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As the uterus swells during pregnancy, the pressure within the abdominal cavity rises by up to 4 cm. As a result, the diaphragmatic excursion is restricted, which may result in more fast and shallow respirations. Pregnant women experience shortness of breath due to an increase in maternal respiratory rate of around two breaths per minute.
References:
Tortora, G. J., & Derrickson, B. H. (2014). Principles of anatomy and physiology (14th ed.). John Wiley & Sons.