What is ones halachic obligation if an ill person passes out and one notices s/he has a DNR bracelet (or notation on their chart)?

What if they're in your home? (i.e., you're in the middle of a meal and they pass out, do you call an ambulance?)
Is there a difference if they're already in the hospital? (i.e., you're visiting and they crash, do you call the nurse?)

On a similar note, would it make a difference whether you call 911 or hatzala? Does the hatzala crew abide by a DNR request?

"Passes out" or drops dead???

if they drop dead, there isn't much to talk about

calling for help is not resuscitation.

DNR is only applicable if their heart stops (or maybe stop breathing). If they are not YET at that point, as you said, there isn't much to talk about......

is it if you call hatzala? do they have to do everything in their power to keep the person alive?

If they are still alive??? Of course....
AFAIK a DNR means don't use artificial means to bring someone BACK, like defib, or respirators. But not to sit there and let someone die...

or any form of CPR.

is not resuscitating the same as sitting there and letting someone die?

Fine, but that is a big difference from someone "passing out", or leaving them until they get to the point where they NEED CPR, when they could have potentially been saved.....

it's not just a random person who passed out; it's a terminally ill person wearing a DNR bracelet meaning that they knew and expected it to happen

No, resuscitating means they are already clinically dead, and you are trying to make their heart beat again, or breathe for them artificially. It doesn't mean their pulse is weakening, and as their breathing is more shallow and you just sit there. (Or if they choke on a piece of kishke you don't do the Heimlich maneuver)....

depends why they "passed out." fainting from heat exhaustion isn't the same as collapsing from cardiac arrest. in the latter case, they're already at that point upon "passing out."

in any case, DNR is an order to medical professionals, not laypeople.

I already covered that possibility with my first post in this thread.....

And we're talking about JEWS here, there ARE no "laypeople".......

To the average layperson, a person is automatically assumed to have a DO resuscitate status.

In the hospital, before somene is made DNR, they have to have advanced directives signed, and there's a whole formal process that makes one officially DNR.

Check out this link for US laws/info:
http://en.wikipedia.org/wiki/Do_not_resusc...e#United_States

Halachah-ly, Jews shouldn't have a DNR, that being said, if I am on duty (& actually, off duty I am still under a "duty to act" rule) I follow what the person has stipulated, so if they have a DNR, I call for back up, but will not do any CPR.

If I didn't have a "duty to act" when off duty...I don't know....but I'd have a hard time just standing around and not doing anything for someone.