The ECG in SHHS1 is a modified lead II. In MrOs there are two electrodes which collect their own signal. One can reference ECG R to ECG L to obtain a modified Lead II signal.
The Nonin 8000J Flex oximeter finger sensor was used and output a plethysomograph signal.
The Compumedics collection software could provide assessment of oximetry quality with a signal called OXSTAT. OXSTAT was calibrated to the oximetry signal and gave 4 levels of signal quality: Good, Marginal, Poor and Off.
The values are as follows:
I doubled checked the data shown in the hypnogram to the previously scored study just to make sure that it is correct, and the hypnograms match. Multiple awakenings are often observed throughout the sleep period. Often people are not aware of these awakenings. You can view the following resource on sleep cycles: https://sleepdisorders.sleepfoundation.org/chapter-1-normal-sleep/sleep-regulation/. Artifacts are taken into consideration when deriving sleep stages and filtering is generally applied before the hypnogram is derived.
Are you mainly concerned if whether the studies distinguished N3 from N4? Or are there other aspects you are interested in?
Both the AASM Alternative Hypopneas and the AASM Recommended Hypopneas did not require a 3% desaturation and/or arousal to be annotated. These events are marked independent of whether any associated desaturation were linked with the event.
The datasets on the NSRR do not have this info.
The PPG signal is not available for the SHHS studies. For adult studies with this signal, I would suggest MESA, Heartbeat, HomePAP, BestAIR, or ABC.
Yes, you are correct that hypopneas were scored from the airflow, thoracic, or abdomen signals for SHHS. I don't believe there is a way to identify which signals were used for hypopnea scoring for SHHS2. Taken from the manual "Variation in signal amplitude on airflow, thoracic and abdominal channels: In some studies, information appears qualitatively different from different channels. Scoring will be done from the channel that correlates the best with the changes in the oxygen saturation. If there are no changes in O2 saturation, scoring will be done from the channel that shows the clearest amplitude variation. In cases where the thermister varies from the inductance channels, and the inductance channels appear mostly artifact free, the inductance channels will be used for event identification and classification. When in doubt, use data from the inductance and saturation channels to identify/classify events." The RESPSCCH variable was not collected for SHHS2. I am not aware of any other variables which would provide the information you seek.
Sleep Heart Health Studies were collected prior to AASM rules and do not follow the standard AASM guidelines for hypopnea scoring. Please refer to the manual referenced above for respiratory event scoring procedures.
Signals such as the ones you list are available in the datasets. Available signals vary per dataset. Individual studies can be downloaded.