Some clarification following our exchange.
As it happen the Pleth channel seems to correspond to the PPG signal provided by the oximeter.
My confusion came from the fact that plethysmography is usually called PPG if we are talking about plethysmography measured using an optical sensor and I was also wondering why not two channels of PPG/Pleth were provided (since the oximeter provides PPG at two wavelengths.) What seems to be is that Pleth == PPG but manufacturer usually do not provide the PPG at two the wavelengths to avoid inverse engineering of the calibration used to derive SpO2 from PPGs. So at this stage I understand that Pleth=PPG but it is unclear to me at what wavelength the optical signal is provided and whether this is raw or preprocessed signal. I am checking that with Natus to see if they have more details.
Thanks for your answer.
I am looking for PPG (Photoplethysmogram) and not Pleth (Plethysmograph) signals. Maybe that was the source of the confusion..
Ideally, I am looking for a large sleep database that has raw PPG, body position, raw EEG with manual sleep stages scoring, raw actigraphy, breathing rate/effort (from Plethysmograph for example or other). Or at least a database with PPG and EEG to start with.
Do you have one you could recommend?
I hope all is well.
I requested and obtained access to the MESA database you suggested in the previous post - but I cannot see raw PPG in it. (I downloaded and opened one of the EDF files to check.)
I would like to check on the other databases you suggested Heartbeat, HomePAP and BestAIR, ABC if this signal is available together with the other traditional PSG ones. Is there a way to check that without requesting access to all these DBs?
Thanks Stephanie, that's very helpful pointers
I will look into these.
I am interested to know if the raw PPG signal is available from the EDF files of the Sleep Heart Study.
It is not listed here (https://sleepdata.org/datasets/shhs/pages/10-montage-and-sampling-rate-information-shhs1.md)
And if not, if it is available for other adult PSG studies?
Thanks for the clarification,
Thanks Mike. That's helpful. Although as I look at the SHHS information it does not look for any of the regular AASM rules for the hypopnea events scoring (AASM mentions desaturations of 3 or 4 % depending on the guideline year, whereas on the SHHS Manual they mention 2% desaturations).
Following up on this discussion, how do we know what AASM guidelines were used for scoring on the different databases?
Also, in addition to the AHI/RDI entries, is there a ''final diagnosis'' from the MD that is provided? (and which is based on both indexes and symptoms as per the ICSD-3)?