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
During the initiation of exercise, there is increased breathing due to the neural changes (i.e., the anticipation of the activity that stimulates the limbic system; sensory impulses from proprioceptors in muscles, tendons, and joints; and motor impulses from the primary motor cortex) that send excitatory impulses to the dorsal respiratory group (DRG).
2. Moderate exercise
During moderate exercise, there is an increased depth of breathing due to the chemical and physical changes in the bloodstream. These changes include decreased PO2, increased PCO2, and increased temperature due to increased consumption of oxygen, increased production of carbon dioxide, and liberation of more heat as more oxygen is used, respectively.
3. Asthma attack
Because of smooth muscle spasms in the walls of smaller bronchi and bronchioles, edema of the mucosa of the airways, increased mucus secretion, and/or damage to the epithelium of the airway, the airways become obstructed (inflamed and swollen) which results to respiratory difficulties. It is harder for air to flow in and out of one’s airways and causes wheezing, breathlessness, chest tightness, and coughing.
4. Abrupt ascent into high altitudes
With the increase in altitude, the total atmospheric pressure and the partial pressure of oxygen decrease, and the oxygen diffuses into the blood more slowly. The lower level of oxygen in the blood causes difficulties in breathing (deep and rapid) and may cause hypoxic hypoxia.
5. Pneumonia
As certain microbes enter the lungs of an individual, they release toxins that stimulate inflammation and immune response that have damaging effects. The toxins and immune response damage alveoli and bronchial mucous membranes; and inflammation and edema cause the alveoli to be filled with fluid, interfering with ventilation and gas exchange, causing difficulty breathing—rapid and shallow.
6. Paralysis of phrenic nerve
The phrenic nerves supply the diaphragm and originate from C3 to C5 and injuries or severing the nerves causes respiratory arrest. The paralysis or damage to the nerve causes breathing to stop as it can no longer send nerve impulses to the diaphragm and may require a ventilator machine to help the patient with paralyzed phrenic nerve breathe.
7. Severe tuberculosis with resulting lung scar tissue
Due to the pulmonary condition tuberculosis (caused by Mycobacterium tuberculosis), the lungs have decreased compliance—it resists expansion. Lung compliance is one of the factors affecting pulmonary ventilation, hence a patient with the condition experiences difficulties in breathing, shortness of breath, coughing, etc.
8. Severe anemia
Oxygen delivery falls due to severe anemia as the oxygen-carrying capacity of blood is reduced. The reduced amount of hemoglobin in the blood causes shortness of breath and hyperventilation as the lungs overcompensate to restore oxygen levels to normal.
9. Advanced COPD (chronic obstructive pulmonary disease)
Advanced chronic obstructive pulmonary disease is characterized by the obstruction (inflamed and narrowed) or collapse of airways which increases resistance. The respiratory disorder causes obstructed airflow making breathing difficult.
10. Advanced pregnancy
Advanced pregnancy prevents complete descent of the diaphragm, the most important muscle for inhalation, and contributes to shortness of breath during pregnancy. The contraction of the diaphragm is responsible for the air that enters the lungs, and the enlarged uterus takes up more space, resulting in pressure against the diaphragm and impeding its contraction.
Reference
G. J. & Derrickson, B. (2014). Principles of Anatomy and Physiology (14th ed.). New York: John Wiley & Sons, Inc.