Why can’t I use a nasal cannula instead of a CPAP nasal pillow mask?

The oxygen nasal cannula looks very similar to the nasal pillow CPAP mask. However, the oxygen nasal prongs rest deeper in the nostrils and will not inflate like the nasal pillows.

Conversely, the nasal pillows cover the nostrils fully, sitting snugly against them, creating a pressure seal. This seal enables CPAP therapy to work.