Date: 201606
Local time of day: 0001-0600
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Second aircraft: Citation V/Ultra/Encore (C560)
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness; Confusion; Communication Breakdown
Second reporter function: Enroute
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Critical; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft RA; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Air Traffic Control Separated Traffic; Air Traffic Control Issued New Clearance; Flight Crew Overcame Equipment Problem; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed in Emergency Condition; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: I was working R45/47 combined. Both aircraft were just west of ZZZ VOR and had been radar handed off to sector 34. I tried to ship the Citation to the next frequency but no response. So I decided to ship the Aircraft Y he took the frequency change. I have not listened to the replay of the situation yet. I tried to ship the Citation one more time. After a slight pause he said they had lost pressurization and needed lower. I said descend and maintain FL380. Aircraft Y was right underneath him and I could not tell which target was which. I called to have sector 34 turn Aircraft Y right and told him I would go left. I asked the pilot if he was able to turn left he said affirmative. I told him turn left. I believe I issued a descent to 32;000 feet at some point because I could see the targets coming apart. I realized that Sector 34 had went left. I did not like that so I told him to maintain FL380.Meanwhile I'm yelling across the room at Sector 34 asking if they went left. He said affirmative. Just then I could tell that we had room to get the Citation down and I gave him the descent to 29;000 feet. Meanwhile I had been coordinating with Sector 44 on the emergency by yelling across the room. At one point when the aircraft was in the high twenties I asked him if he was going to divert. He said maybe and that the pressurization was stabilizing. I gave the pilot a descent to 16;000 feet and was thankful everything worked out. During that Sector 34 thought it would be beneficial to descend the Aircraft Y and turn him back to the right. Happened all within 30 seconds I would guess. Also at one point I remember telling the Citation about the traffic right underneath him.


Second narrative: I had taken the hand off on both Aircraft Y and Aircraft X. Aircraft Y had just checked in at 37;000 feet and Sector 47 who was still talking with Aircraft X at 41;000 feet. The R47 controller calls and says Aircraft X has a pressurization problem and is descending. Aircraft Y was directly beneath Aircraft X approximately a half mile behind. I thought the 47 controller said turn Aircraft Y left. So I immediately turned Aircraft Y left out of the way of the descending aircraft. Then I noticed that both airplanes are now turning left. And I yelled I thought you said left; and he yells turn him right; turn him right.By this time Aircraft Y is further to the left than the descending airplane. I yelled across the room; you want me to turn him right now; and they yelled; turn him right; so I did; which started to bring the airplanes back together because sector 47 was still talking to Aircraft X and I guessed he was going to go further left so I turned Aircraft Y to the right. I explained to the Aircraft Y there was some confusion and now turn right and told him where the traffic was again and that he was descending; at this time; Aircraft Y wanted lower so I yelled to sector 44 and 47 and told them the Aircraft Y is descending to 35;000 feet and then issued the control instruction. I then told Aircraft Y to Fly heading 050 because I felt that would be better than keep him turning right into Aircraft X. Then Aircraft X descended through the altitude of the Aircraft Y approximately a mile and half behind him and off to his right. I then told Aircraft Y that the aircraft was clear of his altitude and to stay on that heading for a second. After I got my bearings; I climbed Aircraft Y back to 37;000 feet and cleared them on course.I had the opportunity to listen to exactly what the R47 controller said; and it was something along the lines of Turn Aircraft Y to the right; I'm turning my guy left. That is when I immediately turned Aircraft Y 30 degrees left. I guess all I heard was left and I didn't even fathom he would be turning the guy that needed the descent. I was previously an airline pilot and during sim training; practicing rapid decompressurazation; as a flight crew; your responsibility is to don your oxygen mask and start a straight forward descent. As a controller I must have thought that's what the pilot is doing; he's going straight down; move the guy below him out of the way and I guess the last word I heard from the R47 controller was left. We also had Military airspace 10 miles or so off the right side so I thought this was the safest way to go. I can think of two recommendations. On my part; I should have confirmed and not just immediately issued the control instruction. But I felt taking action was the quickest thing to do; but my action was wrong. (You want me to go what direction). And second; when we need to make a control instruction to another sector; only give that control instruction; for example. Aircraft X is descending due to a pressurization problem. Turn Aircraft Y Right.


Synopsis: B737-800 flight crew in an emergency descent received an RA on traffic below it that being vectored out of the way.