Answer: Great question. You are correct: pneumonia is a common trigger for COPD exacerbations. Although CPAP is not ideal as a long term solution for patients with pneumonia, respiratory distress and respiratory failure in COPD patients is what we are trying to avoid in the pre-hospital setting.
The reality is that many patients who have been getting CPAP by paramedics probably have had pneumonia given how difficult it is to diagnose without a chest x-ray. Despite this, outcomes are improved with the use of CPAP by paramedics (Ann Emerg Med. 2014;63:600-607.)
The danger here would be to withhold a beneficial therapy from patients who are by definition in respiratory distress based upon a presumptive clinical diagnosis of pneumonia.