Narrative:

I was working 51 manual positions. Aircraft X checked on at FL240 requesting lower because they were running low on oxygen. Directly below the aircraft's path was approach at 15;000 and below. Aircraft X was vectored left to get around approach; because they do not allow overflights; and the aircraft was cleared to 16;000. I used a shout line to approach to point out aircraft X. The response to my point out was a garbled 'thank-you.' I asked for control; but the approach controller had apparently hung up. I noticed the aircraft was descending below 16;000 and recognized it was an emergency to get the aircraft down. I called approach again several times on the shout line saying 'break for control' a few times before they picked up. I asked for and got control for aircraft X. In the descent; aircraft X's mode C showed XXX; indicating a steep descent. In the path of aircraft X was aircraft Y; level at 11;000; inbound to ZZZ on a STAR arrival. Aircraft X's mode C began reporting again as the aircraft passed behind aircraft Y at approximately 1 mile. The mode C of aircraft X showed 10;100. At that point; we realized there was a loss of separation; possible airspace violation and possible pilot deviation. We verified the aircraft was again stable and then vectored aircraft X to the west to get the aircraft back in our airspace.I did not receive coordination with the previous sector about aircraft X's situation; if the pilot had made it known. It would have been easier to assist the pilot if approach was able to answer the line quicker; and when they did; used good phraseology to let me know the aircraft was point out approved and my control before hanging up. I think the pilot did what they had to do to survive; but I would have liked to know how dire the situation was. It seemed like the pilot thought they were running low on oxygen; but were really out. Had we known the aircraft was going to descend that rapidly and in close proximity to aircraft Y; we could have used a more aggressive vector.

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Original NASA ASRS Text

Title: ARTCC Controller reports of an aircraft that needs to descend due to lack of oxygen. Aircraft descends through another Controller's airspace. Aircraft Mode C shows XXX [not known altitude; usually when climbing or descending rapidly] and its path is in conflict with an arrival aircraft. Loss of separation occurs because aircraft in rapid descent Mode C works again and indicates 1;000 FT lower than conflicting traffic.

Narrative: I was working 51 manual positions. Aircraft X checked on at FL240 requesting lower because they were running low on oxygen. Directly below the aircraft's path was Approach at 15;000 and below. Aircraft X was vectored left to get around Approach; because they do not allow overflights; and the aircraft was cleared to 16;000. I used a shout line to Approach to point out Aircraft X. The response to my point out was a garbled 'thank-you.' I asked for control; but the Approach Controller had apparently hung up. I noticed the aircraft was descending below 16;000 and recognized it was an emergency to get the aircraft down. I called Approach again several times on the shout line saying 'break for control' a few times before they picked up. I asked for and got control for Aircraft X. In the descent; Aircraft X's Mode C showed XXX; indicating a steep descent. In the path of Aircraft X was Aircraft Y; level at 11;000; inbound to ZZZ on a STAR arrival. Aircraft X's Mode C began reporting again as the aircraft passed behind Aircraft Y at approximately 1 mile. The Mode C of Aircraft X showed 10;100. At that point; we realized there was a loss of separation; possible airspace violation and possible pilot deviation. We verified the aircraft was again stable and then vectored Aircraft X to the west to get the aircraft back in our airspace.I did not receive coordination with the previous sector about Aircraft X's situation; if the pilot had made it known. It would have been easier to assist the pilot if Approach was able to answer the line quicker; and when they did; used good phraseology to let me know the aircraft was point out approved and my control before hanging up. I think the pilot did what they had to do to survive; but I would have liked to know how dire the situation was. It seemed like the pilot thought they were running low on oxygen; but were really out. Had we known the aircraft was going to descend that rapidly and in close proximity to Aircraft Y; we could have used a more aggressive vector.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.