Central Apnea Index

I have a AirSense 11 machine. I occasionally look at the night's sleep summary and am curious why some of the Apneic Index is Central and some is Obstructive? Does this mean I have both obstructive sleep apnea and central sleep apnea?

No unless you are seeing a central apnea index of over 5 per hour (and you for sure were asleep when they were flagged) every night you don't have central sleep apnea. Just what is your central index?

An occasional central apnea is normal to see.
Example....it's normal to have what is called a sleep onset central when transitioning from awake to asleep.
Another example...the machine can and will flag awake/arousal breathing pauses in breath but if we aren't asleep they aren't real asleep central apneas. The machine only measures air flow or breathing....it doesn't know if we are asleep or not but awake/arousal breathing is very irregular when compared to asleep breathing and it will flag those irregularities as some sort of apnea but they don't mean much because we aren't asleep.

Thanks for your helpful explanation. Last night I had a 2.6 AHI, of which 2.3 was obstructive sleep apnea and 0.3 central sleep apnea.

With that low of a central index.....you do NOT have central apnea.

Are you sleeping soundly for the most part and feeling decent during the day?

Yes, most nights I sleep well and have pretty good energy during the day.