From the Guidelines
CPAP therapy can be used for severe Community-Acquired Pneumonia (CAP) with hypoxemia up to a PaO2/FiO2 ratio of approximately 150 mmHg, as patients with severe hypoxemia beyond this threshold are considered poor candidates for noninvasive ventilation (NIV) and may require immediate intubation 1.
Key Considerations for CPAP Use in CAP
- The decision to use CPAP should be based on the patient's overall clinical condition, including the presence of hypoxemia or respiratory distress, and the absence of immediate need for intubation 1.
- Patients with underlying COPD are most likely to benefit from CPAP therapy, and those with inability to expectorate or excessive sputum production may not be ideal candidates 1.
- Close monitoring is crucial, with reassessment every 1-2 hours initially, to promptly recognize failure of CPAP therapy, which is predicted by failure to improve respiratory rate and oxygenation or decrease carbon dioxide partial pressure (pCO2) in patients with initial hypercarbia 1.
Implementation and Monitoring of CPAP
- When implementing CPAP, start with pressures of 5-10 cmH2O and titrate based on patient response, although the optimal pressure range is not specified in the provided evidence.
- CPAP should be discontinued and intubation considered if there's clinical deterioration, worsening hypoxemia despite CPAP optimization, development of hemodynamic instability, or altered mental status, as these indicate failure of CPAP therapy and potential need for more advanced respiratory support 1.
From the Research
Level of Hypoxemia for CPAP Therapy in Severe Community-Acquired Pneumonia (CAP)
- The level of hypoxemia at which Continuous Positive Airway Pressure (CPAP) therapy can be used for severe Community-Acquired Pneumonia (CAP) is not explicitly stated in the provided studies.
- However, study 2 defines severe acute respiratory failure as a PaO2/FiO2 ratio < 250, and assesses the usefulness of non-invasive ventilation (NIV) in patients with severe community-acquired pneumonia (sCAP) and severe acute respiratory failure.
- Study 3 mentions that a trial of NIV might be considered for select patients with hypoxemic ARF if there are no contraindications, with close monitoring by an experienced clinical team who can intubate patients promptly if they deteriorate.
- Study 4 establishes the American Thoracic Society (ATS) criteria for severe pneumonia, which includes a PaO2/FiO2 < 250 mmHg as a minor criterion.
- Based on these studies, it can be inferred that CPAP therapy may be considered for patients with severe CAP and a PaO2/FiO2 ratio < 250, but the exact level of hypoxemia at which CPAP therapy is indicated is not clearly defined 2, 3, 4.
Predictors of NIV Failure and Hospital Mortality
- Study 2 identifies predictors of NIV failure, including higher chest X-ray score at admission, chest X-ray worsening, and a lower PaO2/FiO2 and higher alveolar-arteriolar gradient (A-aDO2) after 1 hour of NIV.
- The study also identifies predictors of hospital mortality, including higher lactate dehydrogenase and confusion, elevated blood urea, respiratory rate, blood pressure plus age ≥ 65 years at admission, higher A-aDO2, respiratory rate and lower PaO2/FiO2 after 1 hour of NIV and intubation rate 2.
- Study 5 identifies independent predictors of 30-day mortality in patients with severe CAP, including invasive mechanical ventilation, septic shock, worse hypoxemia, and increased serum potassium 5.
Use of NIV and CPAP in Severe CAP
- Study 6 assesses the usefulness of positive end-expiratory pressure (PEEP) in patients with moderate-to-severe hypoxemic ARF secondary to CAP, and finds that 66% of patients benefit from PEEP application 6.
- Study 3 discusses the use of noninvasive strategies such as high-flow nasal therapy (HFNT) or noninvasive ventilation (NIV) in patients with severe CAP, and suggests that HFNT may be the first-line approach in the majority of patients, while NIV may be preferable in those with increased work of breathing, respiratory muscle fatigue, and congestive heart failure 3.