A320 DIVERTS TO CLOSEST ARPT WHEN CAPTAIN IS INCAPACITATED BY BACK PAIN.

Narrative

MY CAPT MENTIONED THAT HIS BACK WAS TENDER. HE APPEARED TO BE IN GOOD HEALTH AS WE TAXIED FOR TKOF. DURING THE CLB TO CRUISE ALT; THE CAPT MENTIONED THAT HE WAS BECOMING MORE UNCOMFORTABLE. AS WE PASSED THROUGH APPROXIMATED FL250; I SUGGESTED THAT HE TRY TO STAND UP AND STRETCH OUT. WE LEVELED OFF AT FL370. THE CAPT SPENT THE ENTIRE CRUISE PHASE OF FLT TRYING TO STRETCH OUT HIS BACK AND MINIMIZE HIS DISCOMFORT. AS THE FLT PROGRESSED; IT WAS APPARENT THAT THE CAPT'S LEVEL OF PAIN AND DISCOMFORT WAS INCREASING. THE CAPT WANTED TO CONTINUE TO ZZZ1 AND EXPRESSED THAT SEVERAL TIMES AS I ASKED IF HE WAS OK. WHEN WE WERE APPROX 250 MI S OF ZZZ1 THE CAPT STARTED SCREAMING IN PAIN AND STATED THAT HE COULD NOT STAND UP. THE ONLY PLACE THAT WAS GIVING HIM ANY COMFORT WAS TO LIE ON THE FLOOR OF THE COCKPIT. HE THEN STARTED ASKING OUR DISTANCE TO ZZZ1 AND OTHER ARPTS. WHEN WE WERE 80 NM TO THE E OF ZZZ2 AND 200 NM S OF ZZZ1; THE CAPT STARTED SCREAMING IN SEVERE PAIN AND STATED THAT WE NEED TO DIVERT TO THE NEAREST ARPT AND GET HIM MEDICAL ATTN. I DECLARED AN EMER AND NOTIFIED ATC THAT WE NEED TO DIVERT TO ZZZ2. WHILE ATC WAS COORDINATING THE DIVERSION; I CONTACTED THE #1 FLT ATTENDANT AND TOLD HER ABOUT THE SITUATION. I EXPLAINED THAT WE WERE DIVERTING TO ZZZ2 AND THAT WE WOULD TAXI TO THE GATE AS USUAL. SHE INFORMED ME THAT WE HAD A DEADHEADING COMPANY PLT ON BOARD AND WANTED TO KNOW IF HE WOULD BE HELPFUL. THE E190 CAPT CAME INTO THE FLT DECK AS WE BEGAN OUR DSCNT TO 16000 FT. HE IMMEDIATELY INFORMED ME THAT HE WAS NOT FAMILIAR WITH THE AIRBUS; BUT HE ASSISTED WITH CHKLISTS AND PA ANNOUNCEMENTS. DURING THE DIVERSION; THE CAPT WAS ARTICULATING HIS DISCOMFORT WITH INCREASING VOLUME. I CALLED ZZZ2 OPS AND INFORMED THEM OF THE SITUATION. I REQUESTED THAT ZZZ2 OPS CALL DISPATCH TO LET THEM KNOW WHAT WAS TAKING PLACE. BTWN COMMUNICATING WITH CAPT; THE FLT ATTENDANTS AND ATC; I WAS UNABLE TO ACKNOWLEDGE THE ACARS MESSAGES DISPATCH WAS SENDING. I SET UP FOR AN ILS RWY 19L APCH INTO ZZZ2. I BRIEFED DEADHEADING PLT OF THE APCH AND ASKED HIM TO RUN THE APCH CHKLIST. I MADE THE FL180 AND 10000 FT CALLS AND FLOWS. AS I ENTERED INTO THE L DOWNWIND; THE CAPT GOT BACK INTO THE L SEAT AND REMAINED THERE FOR THE DURATION OF THE FLT AND TAXI INTO THE RAMP. THE CAPT CONTINUED TO ARTICULATE HIS DISCOMFORT AND THE PAIN APPEARED TO BE INCREASING. THE ACFT WAS ESTABLISHED ON THE LOC AND GLIDEPATH BY APPROX 3000 FT MSL. THE CAPT ASSISTED WITH FINAL CONFIGN; RADIO CALLS AND CHKLISTS FOR THE DURATION OF THE FLT. I MAINTAINED A STABILIZED APCH AND LANDED IN ZZZ2 UNEVENTFULLY. THE PARAMEDICS REMOVED THE CAPT FROM THE ACFT AND LEFT THE AREA. I CONTACTED DISPATCH VIA CELL PHONE AND UPDATED THEM OF THE SITUATION. ANOTHER CAPT WAS CALLED BACK TO THE ARPT TO COMPLETE THE FLT TO ZZZ1. ONCE THE PLAN WAS AGREED UPON; I NOTIFIED THE PAX OF THE SITUATION.