CPAP is generally safe. Except for infrequent complications;
1.Pressure necrosis of skin
Particularly of the nasal bridge. Early application of a colloid dressing (or similar) may help avoid this.
Due to air swallowing. In lengthened CPAP use parallel use of a nasogastric tube may be considered although the risk still lies with an open cardiac sphincter.
3. corneal/ conjunctival irritation due to upper airway leaks.
4.Pneumothorax in at risk patients (e.g. trauma).
Ref; Intensive Care Foundation, 2015