Oxygen Saturation

Hi,

Currently, I am using a nasal mask on my trial mask. Although the data doesn't show significant leak and I expect the results of the pulse oximeter (which I might receive tomorrow) to be okay, I was wondering if a change of mask (i.e. to nasal pillow) could lower oxygen saturation.

I was particularly wondering if oxygen saturation could be low despite not having (significant leaks) or if low oxygen saturation would always go hand in hand with air leaks.

If anything air leaks will improve your oxygen saturation values. CPAP masks have a vent that is open all the time. That is also how you exhale stale air. It does not go back into the machine. It short circuits and goes out the mask vent. The other purpose of the mask vent is to freshen up the air inside the mask. There is a certain design mask purge flow rate that is based on the size of the mask. The larger the volume of the mask the higher the purge rate. If you look in the manual for each mask you will find at the end in the specifications section a value which indicates the volume of the mask. You will also see a graph which shows the purge flow rate vs the pressure. That purge rate will be higher on masks that have a higher volume (dead space).

But to your question. Mask leaks essentially increase the purge rate. This increase the oxygen content in the air your breathe. So, if anything a mask with a high leak rate will increase oxygen in the mask, and as a result increase oxygen in your blood levels.

In theory your O2 monitor should reflect the number of apneas and hypopneas (your AHI). Each one should lower O2. The other hidden issue it might uncover is the impact of flow limitations that are not included in the AHI value.