Final answer:
Hypercapnic respiratory failure is characterized by an excess of CO2 in the blood, leading to respiratory acidosis, which can result from impaired lung function or depressant drugs. The body tries to compensate by adjusting bicarbonate levels. Conversely, respiratory alkalosis happens due to CO2 deficiency, often from hyperventilation, and the body compensates by changing respiratory rates.
Step-by-step explanation:
Hypercapnic respiratory failure occurs when there's an abnormally elevated level of carbon dioxide (CO2) in the blood because the body can't remove CO2 effectively through the lungs. This condition is often triggered by diseases that impair the respiratory system, such as pneumonia or congestive heart failure. Drugs like morphine and barbiturates can also cause hypoventilation leading to hypercapnia. Unlike hypocapnia, where there are abnormally low blood CO2 levels, hypercapnia can cause respiratory acidosis, a state in which blood becomes too acidic due to increased carbonic acid from the accumulated CO2. The kidneys attempt to compensate by increasing bicarbonate levels, maintaining the bicarbonate to carbonic acid ratio at a stable level.
Conversely, respiratory alkalosis occurs when there's a carbonic acid/CO2 deficiency in the blood, usually as a result of hyperventilation. Conditions such as fever, infections, and emotional upset can lead to an elevated respiratory rate causing this imbalance. The body's respiratory compensation mechanism works to correct metabolic acidosis by increasing the respiratory rate to expel CO2, while metabolic alkalosis is less effectively compensated for because the body can only decrease the breathing rate to a certain extent to conserve CO2.