From the Guidelines
Type 2 respiratory failure is primarily caused by conditions that lead to hypoventilation, resulting in carbon dioxide retention and hypoxemia, with the most common causes being chronic obstructive pulmonary disease (COPD), severe asthma, neuromuscular disorders, chest wall deformities, central nervous system depression, and obesity hypoventilation syndrome, as noted in the BTS guideline for oxygen use in adults 1.
Causes of Type 2 Respiratory Failure
The causes of type 2 respiratory failure can be categorized into several key groups:
- Chronic obstructive pulmonary disease (COPD) and severe asthma, which increase airway resistance and make it difficult to breathe out carbon dioxide
- Neuromuscular disorders like myasthenia gravis and Guillain-Barré syndrome, which weaken the respiratory muscles
- Chest wall deformities such as kyphoscoliosis, which mechanically limit chest expansion
- Central nervous system depression from drug overdose or brain injury, which decreases the respiratory drive from the brain
- Obesity hypoventilation syndrome, which can lead to both decreased respiratory drive and increased resistance to breathing
- Sleep apnea, particularly during sleep, can also contribute to type 2 respiratory failure by causing intermittent hypoventilation
Treatment Approach
The treatment of type 2 respiratory failure should focus on addressing the underlying cause, with options including oxygen therapy, non-invasive ventilation like BiPAP, or mechanical ventilation in severe cases, as recommended by the British Thoracic Society guidelines for home oxygen use in adults 1. Key considerations in treatment include:
- Careful administration of oxygen to avoid worsening CO2 retention
- Use of non-invasive ventilation with appropriate settings (e.g., IPAP 12-20 cmH2O and EPAP 4-6 cmH2O) for patients with chest wall or neuromuscular disease
- Initiation of bronchodilators and steroids for COPD exacerbations, treatment of neuromuscular disorders, or weight loss for obesity hypoventilation syndrome to address the underlying condition
- Consideration of additional long-term oxygen therapy (LTOT) if hypoxemia is not corrected with non-invasive ventilation alone, particularly in patients with severe restrictive disease or co-existing airways disease or obesity.
From the Research
Causes of Type 2 Respiratory Failure
The causes of type 2 respiratory failure can be attributed to various factors, including:
- Chronic obstructive pulmonary disease (COPD) [(2,3,4,5)]
- Impairment of gas exchange, resulting in failure to meet the body's metabolic demands 6
- Numerous diseases and conditions that can impair gas exchange, such as asthma, cystic fibrosis, and interstitial lung disease [(6,4)]
- Ventilation-perfusion inequality, which is the underlying abnormality determining hypoxemia and hypercapnia in lung diseases 4
- Sleep disordered breathing, which is closely associated with persistent hypercapnic respiratory failure in advancing chronic obstructive pulmonary disease and cystic fibrosis 4
Underlying Mechanisms
The underlying mechanisms of type 2 respiratory failure include:
- Significant ventilation/perfusion mismatching with a relative increase in the physiological dead space, leading to hypercapnia and acidosis 2
- Shift to a rapid shallow breathing pattern and a rise in the dead space/tidal volume ratio of each breath, resulting from adaptive physiological responses 2
- Inability of ventilation to match increasing cardiac output, limiting exercise capacity as the disease progresses 4
- Deteriorating hypoxemia during exacerbations, reflecting the falling mixed venous oxygen tension from increased respiratory muscle activity 4
Clinical Presentations
The clinical presentations of type 2 respiratory failure depend on the underlying cause and the level of hypoxemia and hypercapnia 6, and may include:
- Acute exacerbations of COPD, characterized by increased symptoms and decreased lung function [(2,3,5)]
- Hypoxemia and hypercapnia, which can lead to respiratory acidosis and other complications [(2,6,4,5)]