I. Clinical Manifestations of Respiratory Failure

I. Clinical Manifestations of Respiratory Failure

The primary symptoms are hypoxemia and hypercapnia.

1. Hypoxemia: PaO2 < 6.67 kPa: ① Patients exhibit cyanosis of the lips and nail beds, which is the most important sign of hypoxemia; however, due to factors such as the patient's normal hemoglobin levels, skin pigmentation, and cardiac function status, it can be difficult for the degree of cyanosis to correlate directly with the severity of hypoxia. ② In addition to cyanosis, patients may also experience agitation, convulsions, seizures, or loss of consciousness. ③ Hypoxia has a significant impact on the cardiovascular system, first causing an increased heart rate and elevated blood pressure, which can lead to arrhythmias and shock. Due to the constriction of pulmonary vessels, pulmonary hypertension and right heart failure may develop.

2. Hypercapnia (respiratory acidosis): The accumulation of CO2 can lead to severe central nervous system symptoms and cardiovascular symptoms. Central nervous system symptoms include drowsiness, coma, agitation, and convulsions; muscle tone may increase or decrease, and tendon reflexes may become enhanced or weakened. Because cerebral blood vessels undergo compensatory dilation, intracranial pressure rises, and fundoscopic examination may reveal papilledema, constricted pupils, and unequal pupil sizes—these are clinical manifestations of severe respiratory failure, sometimes referred to as pulmonary encephalopathy. Cardiovascular symptoms may include chest pain, chest tightness, palpitations, rapid pulse, and elevated blood pressure; in advanced stages, severe hypercapnia may occur, at which point blood pressure begins to decline. Peripheral vasodilation may cause congestion of the conjunctiva, and some patients may experience arrhythmias. In addition to changes in the lungs and heart, various organs and systems may exhibit symptoms caused by insufficient oxygen and excessive carbon dioxide, such as ulcers, upper gastrointestinal bleeding, liver and kidney dysfunction, and severe electrolyte imbalances. Both metabolic acidosis and respiratory acidosis can occur.