3.13 : 急性呼吸衰竭 III：高碳酸性呼吸衰竭

Type 2 or hypercapnic respiratory failure occurs due to increased carbon dioxide production or decreased alveolar ventilation.

It is characterized by arterial carbon dioxide or PaCO2 exceeding 45mmHg and a pH below 7.35.

Conditions causing hypercapnic respiratory failure can be categorized into four groups.

First, airway and alveoli abnormalities like asthma and cystic fibrosis can lead to airway obstruction or air trapping, necessitating increased inspiratory effort for sufficient tidal volume.

It results in respiratory muscle fatigue and eventual ventilatory failure.

Next, central nervous system abnormalities, such as opioid overdoses, suppress the breathing drive by reducing the brainstem's sensitivity to carbon dioxide, leading to elevated PaCO2 levels.

Additionally, chest wall abnormalities, such as flail chest, limit lung and diaphragmatic movement due to pain and mechanical restriction from rib fractures.

Finally, neuromuscular diseases like Guillain-Barré syndrome can cause respiratory muscle weakness or paralysis.

When respiratory muscles are compromised, they fail to maintain normal PaCO2 levels, leading to respiratory failure.