I am having difficulty wrapping my head around the new SDE Oxygen definition:

SDE Oxygen 60 Minutes Or Less Prior To ED Admission Or During ED
"Initial Population" InpatientEncounter
let LastEDVisit: LastEDEncounter(InpatientEncounter),
Oxygen: ( ["Intervention, Order": "Non Invasive Oxygen Therapy by Nasal Cannula or Mask"]
union ["Intervention, Performed": "Non Invasive Oxygen Therapy by Nasal Cannula or Mask"]
union ["Device, Order": "Non Invasive Oxygen Therapy Device Codes"] ) Oxygen
where (Coalesce (start of Global."NormalizeInterval" (Oxygen.relevantDatetime, Oxygen.relevantPeriod), Oxygen.authorDatetime) during LastEDVisit.relevantPeriod
or Coalesce (start of Global."NormalizeInterval" (Oxygen.relevantDatetime, Oxygen.relevantPeriod), Oxygen.authorDatetime) 60 minutes or less before or on start of LastEDVisit.relevantPeriod)

I understand the intention is to filter the list of encounters that are in the Initial Population to encounters where the patient has had oxygen therapy either during the ED or up to 60 minutes prior. As written, I don't think this is what will happen.

The where clause in the above definition will not filter the list returned by "Initial Population" but will filter the list of Oxygen Therapies (interventions and devices) that are retrieved and unioned together. The ELM appears to support my conclusion.

Please let me know if I am mistaken, but as is I believe this is just going to return all encounters returned by "Initial Population".