B737 FLT ATTENDANT EXPERIENCES POSSIBLE HYPOXIC SIGNS DURING CRUISE.

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ON TAXI; IMMEDIATELY PRIOR TO TKOF; I EXPERIENCED TINGLING SENSATIONS IN MY HANDS. THIS TINGLING CONTINUED AND AT CRUISE ALT OF FL390 MY FEET BEGAN TINGLING AS WELL. HAVING PREVIOUSLY EXPERIENCED A SLOW DECOMPRESSION ON A B737 AND BEING AWARE THAT THESE SENSATIONS INDICATED I WAS GOING INTO A HYPOXIC STATE; I BECAME QUITE ALARMED. I ASKED MY FLYING PARTNER IF SHE WAS EXPERIENCING THESE SYMPTOMS AND SHE REPLIED NEGATIVELY. SHE WAS ALSO QUITE A BIT HEAVIER THAN I AM. I CALLED THE COCKPIT IMMEDIATELY AND REQUESTED AN INCREASE IN AIR FLOW. I ALSO ASKED THE FO IF THEY MANIPULATED THE AIR FLOW TO INCREASE FUEL CONSUMPTION. HE REPLIED THAT THEY DID NOT. WITHIN 1 MIN MY HYPOXIC SYMPTOMS WERE GONE. I CALLED THE COCKPIT TO LET THEM KNOW THIS AND THE CAPT ASKED ME TO COME UP WHEN THEY NEEDED A BREAK. I DID THIS AND THE FO LEFT THE COCKPIT. CAPT THEN INFORMED ME THAT ON 'LONG HAULS' HE DID MANIPULATE THE OUTSIDE AIR FLOW TO INCREASE FUEL EFFICIENCY. AT THIS POINT I REALIZED THAT AIR QUALITY (AND MY BRAIN CELLS) WAS BEING COMPROMISED IN THE PURSUIT OF FUEL EFFICIENCY. I BELIEVE THIS SITUATION IS AN ALARMING ONE AND THAT ALL FLT CREWS SHOULD BE AWARE OF THE SYMPTOMS OF HYPOXIA AND THE CONSEQUENCES OF MANIPULATING AIR FLOW TO THE DETRIMENT OF AIR QUALITY.