From the Guidelines
CPAP is generally not appropriate for type 2 respiratory acidosis, and BiPAP is the preferred non-invasive ventilation option for these patients. Type 2 respiratory acidosis is characterized by hypoventilation and CO2 retention, typically seen in conditions like COPD, neuromuscular disorders, or opioid overdose. For these patients, BiPAP provides both inspiratory (IPAP) and expiratory (EPAP) pressure support, which helps augment ventilation and clear CO2, directly addressing the underlying hypoventilation 1.
Key Considerations
- CPAP, which delivers constant pressure throughout the respiratory cycle, primarily improves oxygenation but does not significantly enhance ventilation or CO2 clearance 1.
- In fact, CPAP may sometimes worsen CO2 retention in patients with severe COPD by increasing work of breathing.
- For acute type 2 respiratory failure, typical BiPAP settings might start with an IPAP of 10-12 cmH2O and EPAP of 4-5 cmH2O, titrated based on patient response, blood gases, and comfort 1.
- If BiPAP fails to improve ventilation, intubation and mechanical ventilation may be necessary.
Clinical Guidelines
- The BTS guideline for oxygen use in adults in healthcare and emergency settings recommends starting NIV with targeted oxygen therapy if respiratory acidosis persists for more than 30 min after initiation of standard medical management 1.
- The 2016 ESC guidelines for the diagnosis and treatment of acute and chronic heart failure recommend non-invasive positive pressure ventilation (CPAP, BiPAP) in patients with respiratory distress and started as soon as possible to decrease respiratory distress and reduce the rate of mechanical endotracheal intubation 1.
Patient Management
- Monitoring of transcutaneous arterial oxygen saturation (SpO2) and measurement of blood pH and carbon dioxide tension are crucial in managing patients with type 2 respiratory acidosis 1.
- Oxygen therapy should be used judiciously, avoiding excessive oxygen use in patients with COPD, as it may increase the risk of respiratory acidosis 1.
From the Research
CPAP Appropriateness for Type 2 Respiratory Acidosis
- The use of Continuous Positive Airway Pressure (CPAP) in patients with type 2 respiratory acidosis is not directly addressed in the provided studies, except in the context of specific conditions such as obstructive sleep apnea (OSA) or chronic obstructive pulmonary disease (COPD) 2, 3, 4, 5, 6.
- However, study 4 compares the effectiveness of bi-level positive airway pressure (BiPAP) and CPAP in patients with acute hypercapnic respiratory failure (AHRF) due to etiologies other than COPD, and finds no significant difference between BiPAP and CPAP in reducing the rates of endotracheal intubation and mortality.
- Study 2 discusses the treatment of respiratory acidosis, which may include invasive or noninvasive ventilatory support, but does not specifically mention CPAP as a treatment option for type 2 respiratory acidosis.
- Study 6 focuses on the use of non-invasive ventilation (NIV) in COPD patients with acute type 2 respiratory failure, and recommends the use of bi-level positive airways pressure units, but does not discuss CPAP specifically.
- Studies 3 and 5 discuss the use of CPAP in patients with OSA, and its effects on glucose metabolism in patients with type 2 diabetes, but do not address its use in type 2 respiratory acidosis directly 3, 5.