MLG HAS PRESSURIZATION PROB; MAKES DSCNT PRIOR TO NOTIFYING ATC.

Narrative

AFTER TKOF FROM OKC CLBING THROUGH 10000 FT TO AN ALT OF 16000 FT; I NOTICED THAT THE CABIN PRESSURE ALT WAS CLBING RAPIDLY AND APCHING THE AMBIENT ALT OF THE ACFT. I NOTIFIED CTR THAT WE HAD TO LEVEL AND WE HAD A POSSIBLE PROB. WE WERE ASSIGNED 13000 FT AND THE COPLT; WHO WAS FLYING; LEVELED THE ACFT AT 13000 FT. I CONTINUED TO MONITOR THE PRESSURE ALT OF THE CABIN AND DETERMINED THAT WE HAD LOST PRESSURIZATION. I TRIED TO TELL THE CTR CTLR WE NEEDED LOWER AND INSTRUCTED THE COPLT TO START A DSCNT. SIMULTANEOUSLY I SELECTED MANUAL CTL OF THE PRESSURIZATION AND ATTEMPTED TO DECREASE THE CABIN ALT WHICH WAS ALMOST AT 13000 FT. I REGAINED CTL OF THE CABIN AND NOTIFIED CTR AS SUCH AND ASKED WHAT ALT THEY WANTED US AT. CTR SAID WE BETTER BE AT 13000 FT. WHEN THE COPLT NOTED THAT THE PRESSURIZATION PROB WAS SOLVED; HE HAD LEVELED AT 12000 FT. I TOLD THE COPLT TO CLB; BUT HE WAS SLOW TO REACT AND SOMEWHAT UNSURE OF WHAT TO DO SINCE HE HAD MISSED THE CTLR'S INSTRUCTION. DURING THIS EVENT; I WAS OVERLOADED BY HAVING TO TALK TO CTR; CTL THE PRESSURIZATION IN MANUAL AND COMMUNICATE WITH THE COPLT. IN HINDSIGHT; AN EMER SHOULD HAVE BEEN DECLARED EARLIER TO ALLOW THE CTLR TIME TO REACT.