In Lab vs At Home sleep study.

[breathingeasy]

My sleep doctor gave me the choice of in-lab or at home study. For convenience sake I chose at home and did two nights with electrodes attached, etc. The results confirmed sleep apnea (on a scale of 1-10, my doc classified me as a 9.5) with 45+ events per hour. All this to say that the home test yielded enough data to warrant CPAP intervention. Been on CPAP since 2015.

[jstro84]

"I've heard, meaning I can't verify this, but stopping CPAP use 5 to 7 days in advance of the sleep study will eliminate any residual therapy benefit by the CPAP." - Crimson Nape

This is really interesting, and I wonder if it impacted my HST with the ResMed AirLink. The HST measured AHI of 9 (reportedly, I don't have the actual data) whereas my initial treatment with low pressure (4cm H2O) CPAP had an AHI as high as 18. 

I didn't stop CPAP use before my HST and I wonder if I would have gotten different results otherwise. Also interesting that there are "residual therapy benefits" from using CPAP even if you discontinue use for a bit. 

[dataq1]

The jury seems to be still out on the “does therapy linger”.
Some Docs want a clean slate (a respite from therapy) while others seem to say ‘it makes no difference’.
Obviously it would require a controlled experiment or clinical trial to assert one position or another. I just have not heard of any study that examined that.

All that being said, the Drs first obligation is to “First Do no harm”. If a patient might suffer some significant injury by pausing therapy in order to get a “clean read”, that would be a big problem. 
Generally Drs are risk adverse, so it is unsurprising what their pre-test instructions tend to be.