Respiratory acidosis occurs when acute or chronic derangements of the respiratory system lead to inefficient clearance of carbon dioxide. These derangements may involve:
Primary disease of the lung parenchyma
Problems with the chest wall
A disorder of central control of ventilation.
When alveolar gas exchange units are unable to sufficiently excrete carbon dioxide, this leads to an increase in the arterial carbon dioxide levels above the normal range of 35 to 45 mmHg (4.7-6.0 kPa). With the increase in carbon dioxide, hydrogen ions accumulate, causing the arterial pH to fall below the normal range (i.e., <7.35).
Respiratory acidosis may be acute or chronic. Acute respiratory acidosis is usually secondary to acute respiratory failure.
In acute respiratory failure, there is insufficient buffering capacity to handle the dramatic increase in arterial and venous carbon dioxide. Over time, more and more carbon dioxide is processed by carbonic anhydrase to bicarbonate (the Hamburger shift). This leads to chloride excretion by the kidney with ammonium, and the pH gradually rises.
The consequences of failing to recognise acute respiratory failure include marked hypoxaemia, hyperkalaemia, cardiovascular instability, and cardiac arrest.
- Multilobar pneumonia
- Foreign body aspiration
- Drug use (narcotics, alcohol, sedatives, anaesthetics)
- Oxygen therapy in COPD
- CNS infarct or haemorrhage
- Head trauma
- CNS infection
- Hypoventilation syndrome in obesity
- Pleural effusion
- Inadequate mechanical ventilation
- Cardiogenic pulmonary oedema
- Acute lung injury/acute respiratory distress syndrome
- Pulmonary fibrosis
- Status asthmaticus
- Primary alveolar hypoventilation
- Flail chest
- Ankylosing spondylitis
- Paralytic agents and organophosphates
- High cord trauma/lesions (above C4)
- Guillain-Barre syndrome
- Multiple sclerosis
- Myasthenia gravis
- Muscular dystrophy
- Amyotrophic lateral sclerosis
- Polymyositis and dermatomyositis
- Phrenic nerve trauma
- Fever/malignant hyperthermia
- Insufflation of CO₂ into body cavity (e.g., laparoscopic surgery)
- Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: 2023 report
- German national guideline for treating chronic respiratory failure with invasive and non-invasive ventilation: revised edition 2017
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