C172 PILOT REPORTS STRANGE TINGLING SENSATIONS WHILE VFR AT 4500 FT; AND ELECTS TO LAND IMMEDIATELY FEARING HYPOXIA.

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AFTER DEPARTING AT XA32; I ESTABLISHED A CLB AT 500 FPM TO AN ALT OF 6500 FT MSL. I CONTACTED APCH FOR FLT FOLLOWING. UPON REACHING 6500 FT MSL; I WAS SEEING SCATTERED CLOUDS AND DECIDED TO DSND BACK TO 4500 FT MSL. I MAINTAINED 6500 FT FOR ABOUT 5 MINS BEFORE DECIDING TO DSND. I DSNDED TO 4500 FT MSL AT A RATE OF 500-700 FPM. I WAS ESTABLISHED AT 4500 FT MSL S OF ZZZ AND CROSSED ZZZ AT XA59. I CONTINUED AT THIS ALT FOR AT LEAST ANOTHER 15 NM. APCH NOTIFIED ME OF ACFT INBOUND TO THEIR ARPT. I CONFIRMED VISUAL CONTACT OF 4 ACFT INBOUND. THEY WERE ALL NO FACTOR. AT THIS TIME I FELT FULLY ALERT AND FINE. AT ABOUT 15 NM N OF ZZZ AND WHILE OUTSIDE OF THE CLASS B AIRSPACE; I BEGAN TO FEEL WHAT I THOUGHT WAS RAINDROPS ON THE BACKS OF MY HANDS. THIS CONFUSED ME A BIT AND I FELT FOR SOMETHING WET; BUT IT WAS NOT WET. THIS SENSATION CONTINUED AND PROGRESSIVELY INCREASED UP MY R ARM AND IN MY FEET. I ALSO NOTICED MY HEAD FELT FOGGY AND MY BREATHING BECAME MORE RAPID. I ASKED MY PAX HOW HE FELT; AND HE CONFIRMED THE SAME SYMPTOMS. WE HAD JUST TURNED THE HEAT FULL ON 2 MINS EARLIER. I IMMEDIATELY SHUT OFF THE HEAT AND OPENED ALL THE VENTS. BECAUSE THE ONSET OF THIS SENSATION DEVELOPED SO RAPIDLY; I DID NOT WANT TO WAIT AND SEE IF IT WORSENED OR PROGRESSED ANY FURTHER. I CALLED APCH AND TOLD THEM I WOULD LIKE TO COME IN FOR A LNDG AS I WAS FEELING FUNNY. I REQUESTED VECTORS TO LAND. THEY BROUGHT ME IN WITH VECTORS. I SAFELY LANDED THE ACFT. I WAS GREETED WITH PARAMEDICS. I FELT FINE AT THIS TIME; STILL A LITTLE FUZZY-HEADED; BUT NOW A LITTLE NERVOUS ABOUT ALL THE ATTN. I DID NOT DECLARE AN EMER LNDG AND I DID NOT EXPECT ALL THE ATTN. WHILE COMING IN; ATC ASKED ME TO CLARIFY MY CONDITION; AND I TOLD THEM I FELT PINPRICKS IN MY HANDS AND FEET AND A LITTLE FUZZY-HEADED. I BELIEVE I EXPERIENCED HYPOXIA. IT CONFUSES ME THOUGH THAT IT AFFECTED BOTH MYSELF (A NON SMOKER) AND MY PAX (A SMOKER) AT EXACTLY THE SAME TIME. ALSO; I'M SURPRISED AT THE OCCURRENCE AT THIS ALT WHEN WE WERE NOT AT 6500 FT MSL FOR MORE THAN 5 MINS AND ESTABLISHED AT 4500 FT MSL FOR OVER 10 MINS BEFORE EXPERIENCING THE SYMPTOMS. BUT; ALL THE SYMPTOMS POINT TO HYPOXIA. I BELIEVE I MADE THE RIGHT DECISION TO MAKE A PRECAUTIONARY LNDG. TO AVOID THIS SITUATION IN THE FUTURE; I WILL GO WITH AN INSTRUCTOR TO HIGH ALT AND ACCLIMATE MYSELF TO HIGH ALT FLT. THE ACFT WAS INSPECTED FOR A CARBON MONOXIDE LEAK; BUT NONE WAS FOUND.