From the Guidelines
CPAP is generally not appropriate for type 2 respiratory acidosis, as it primarily treats upper airway obstruction and does not provide ventilatory support to help eliminate CO2. Type 2 respiratory acidosis is characterized by hypoventilation and CO2 retention, often due to conditions like COPD, neuromuscular disorders, or central respiratory depression. For type 2 respiratory acidosis, BiPAP (Bilevel Positive Airway Pressure) is typically more appropriate as it provides both inspiratory (IPAP) and expiratory (EPAP) pressure support 1. Initial BiPAP settings often start with an IPAP of 10-12 cmH2O and EPAP of 4-5 cmH2O, which can be titrated based on patient response and arterial blood gases. The pressure differential between IPAP and EPAP helps increase tidal volume and minute ventilation, facilitating CO2 removal.
Some key points to consider in the management of type 2 respiratory acidosis include:
- Monitoring of transcutaneous arterial oxygen saturation (SpO2) and measurement of blood pH and carbon dioxide tension (possibly including lactate) 1
- Oxygen therapy is recommended in patients with AHF and SpO2 <90% or PaO2 <60 mmHg (8.0 kPa) to correct hypoxaemia 1
- Non-invasive positive pressure ventilation (CPAP, BiPAP) should be considered in patients with respiratory distress (respiratory rate >25 breaths/min, SpO2 <90%) and started as soon as possible in order to decrease respiratory distress and reduce the rate of mechanical endotracheal intubation 1
- In severe cases or if BiPAP fails, invasive mechanical ventilation may be necessary 1
- Addressing the underlying cause of hypoventilation is also essential for effective management of type 2 respiratory acidosis.
It's worth noting that the most recent and highest quality study 1 provides guidance on the use of non-invasive positive pressure ventilation in patients with acute heart failure, which may be relevant to the management of type 2 respiratory acidosis. However, the study emphasizes the importance of careful patient selection and monitoring to ensure effective treatment and minimize potential side effects.
From the Research
CPAP Appropriateness for Type 2 Respiratory Acidosis
- CPAP (Continuous Positive Airway Pressure) is commonly used to treat obstructive sleep apnea (OSA) and other respiratory conditions 2, 3.
- However, its effectiveness in treating type 2 respiratory acidosis, a condition characterized by increased arterial partial pressure of carbon dioxide, is not well established.
- A study on the effect of CPAP treatment on venous lactate and arterial blood gas among obstructive sleep apnea syndrome patients found that CPAP treatment could reduce serum lactate and increase pH in OSAS patients, which might alleviate acid-base balance disorders in OSAS 3.
- Another study compared the effectiveness of bi-level positive airway pressure (BiPAP) and CPAP in patients with acute hypercapnic respiratory failure (AHRF) due to etiologies other than chronic obstructive pulmonary disease (COPD), and found that BiPAP and CPAP had similar efficacy in reducing the rates of endotracheal intubation and mortality in patients with AHRF due to acute cardiogenic pulmonary edema (ACPO) 4.
- Non-invasive ventilation (NIV), including bi-level positive airways pressure units, is recommended for the management of acute type 2 respiratory failure in patients with chronic obstructive pulmonary disease (COPD) 5.
- There is limited evidence on the use of CPAP specifically for type 2 respiratory acidosis, and more research is needed to determine its effectiveness in this context 6, 4.