MD80 FLT CREW EXPERIENCES LOW FLOW AT FL350 WITH WING AND ENG ANTI-ICE ON. CABIN ALT BEGINS TO CLB AND AN EMER DSCNT IS INITIATED WITH LNDG AT DEST ARPT.

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CRUISING AT FL350 IN ICING CONDITIONS WITH ENG AND AIRFOIL ANTI-ICE ON; 'PRESSURIZATION FLOW' LIGHT ILLUMINATED ALONG WITH AN INITIALLY SLOW CABIN CLB. A QUICK CHK AROUND THE COCKPIT SHOWED ALL OTHER INDICATIONS NORMAL. WE REQUESTED AND RECEIVED A LOWER ALT FROM ATC; BUT ALMOST IMMEDIATELY THE CABIN BEGAN CLBING RAPIDLY. DECLARED EMER; REQUESTED 10000 FT; ACCOMPLISHED CHKLIST. CABIN NEVER CLBED ABOVE 10000 FT; OXYGEN MASKS DID NOT DROP IN CABIN. THERE WERE TSTMS IN THE AREA; WE GOT CONTINUOUS MODERATE TURB AT 10000 FT AND IT DID NOT SMOOTH OUT UNTIL ABOUT 40 MI OR SO FROM ZZZ AT 8000 FT. A PAX REQUESTED PARAMEDICS AT THE GATE; WAS FEELING ILL FROM WHAT I BELIEVE TO BE THE BUMPY RIDE. COUPLE ADDITIONAL COMMENTS IN REGARDS TO THE EVENT. INITIALLY; WHEN WE FIRST STARTED TO LOSE THE CABIN; IT APPEARED THAT BOTH PACKS WERE OPERATING NORMALLY. AFTER WE STARTED THE EMER DSCNT; I REALLY DIDN'T LOOK AT THEM AGAIN AS I WAS CONCENTRATING ON JUST GETTING DOWN TO A HABITABLE ALT AS QUICKLY AND SAFELY AS POSSIBLE. ADDITIONALLY; SOMEWHERE BTWN 18000 FT AND 15000 FT OR SO THE AUTOPLT DISENGAGED; PROBABLY DUE TO THE TURB. I ENDED UP HAND-FLYING THE ACFT MOST OF THE WAY TO ZZZ AFTER THAT. ONCE IT SMOOTHED OUT; TRIED THE AUTOPLT AGAIN AND IT STAYED ENGAGED. IT HAS ALSO OCCURRED TO ME THAT I BELIEVE WE NEVER ASKED ATC TO NOTIFY THE COMPANY; LOTS OF THINGS GOING ON. WHEN WE FINALLY ARRIVED AT THE GATE; THE AGENT WAS SURPRISED THAT WE HAD BEEN AN EMER ACFT. NEXT TIME; IF ANOTHER EMER HAPPENS; I WILL TRY TO NOTIFY SOMEBODY; TIME AND CONDITIONS PERMITTING.