From the Guidelines
Respiratory acidosis is primarily caused by hypoventilation, which leads to carbon dioxide retention in the body, and the main causes include respiratory center depression, neuromuscular disorders, chest wall abnormalities, and pulmonary diseases, as stated in the BTS guideline for oxygen use in adults in healthcare and emergency settings 1. The causes of respiratory acidosis can be categorized into several groups, including:
- Respiratory center depression from drugs like opioids, benzodiazepines, and barbiturates
- Neuromuscular disorders such as myasthenia gravis, Guillain-Barré syndrome, and amyotrophic lateral sclerosis
- Chest wall abnormalities including flail chest, kyphoscoliosis, and obesity hypoventilation syndrome
- Pulmonary diseases like severe asthma, chronic obstructive pulmonary disease (COPD), pneumonia, pulmonary edema, and acute respiratory distress syndrome
- Mechanical ventilation with inadequate settings can also cause respiratory acidosis, as noted in the BTS guideline for ventilatory management of acute hypercapnic respiratory failure in adults 1. Respiratory acidosis occurs because reduced ventilation prevents adequate elimination of carbon dioxide, which dissolves in blood as carbonic acid, lowering blood pH and disrupting the body's acid-base balance, as explained in the carbon dioxide physiology section of the BTS guideline for oxygen use in adults in healthcare and emergency settings 1. Prompt identification and management of the underlying cause is essential to prevent complications like hypoxemia, organ dysfunction, and in severe cases, respiratory failure, as emphasized in the initial hospital management of patients with exacerbation of COPD section of the BTS guideline for oxygen use in adults in healthcare and emergency settings 1. It is also important to note that excessive oxygen use can lead to respiratory acidosis in patients with COPD, and targeted lower concentration oxygen therapy should be used to avoid this complication, as recommended in the BTS guideline for oxygen use in adults in healthcare and emergency settings 1.
From the Research
Causes of Respiratory Acidosis
Respiratory acidosis is a condition that occurs when the lungs cannot remove all the carbon dioxide the body produces, leading to an imbalance in the body's acid-base balance. The causes of respiratory acidosis can be categorized into several main groups:
- Disorders affecting gas exchange across the pulmonary capillary 2
- Disorders of the chest wall and the respiratory muscles 2
- Inhibition of the medullary respiratory center 2
- Alveolar hypoventilation, which can be caused by various factors such as drug-induced respiratory depression 3
- Chronic obstructive lung disease, which can lead to carbon dioxide retention and respiratory acidosis 4
Mechanisms of Respiratory Acidosis
Respiratory acidosis can be acute or chronic, with initial metabolic compensation to increase HCO3- concentrations by intracellular buffering 5. Chronic respiratory acidosis results in longer lasting increases in renal reabsorption of HCO3- 5. The condition can also be associated with hypoxemia, especially when patients are inspiring room air 5.
Clinical Presentations
Respiratory acidosis can present with severe symptoms, including deteriorating level of consciousness and desaturation 3. Arterial blood gas evaluation can reveal severe acute on chronic respiratory acidosis, with high PCO2 levels and low pH 3. Treatment of respiratory acidosis may involve noninvasive positive pressure ventilation (NIV) and correction of underlying metabolic alkalosis 3, 4.