CONCERNED ABOUT AN UNRESPONSIVE PAX WITH KNOWN PHYSICAL PROBS; A PLT DEVIATES FROM HIS INST APCH CLRNC IN BOTH ALT AND TRACK. ATC QUERIES AS TO WHAT THE PROB IS. A SUBSEQUENT VISUAL APCH IS FLOWN.

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THIS FLT WAS AN ANGEL FLT ORIGINATING FROM ZZZ WITH AN IFR RELEASE TO FLY THE 'STANDARD DEP; EXPECT RADAR VECTORS TO VOR #1 AND THEN AS FILED CLB AND MAINTAIN 4000 FT.' THERE WERE 2 PAX ON BOARD WITH SOME UNKNOWN PHYSICAL AND MENTAL IMPAIRMENTS. ENRTE; N OF XXXXX INTXN; I WAS QUERIED BY ATC REGARDING HDG. THE COURSE REFLECTED THE ORIGINAL FLT PLAN VOR #1 (V-XXX VOR #2). ATC ISSUED VECTORS TO INTERCEPT VYYY. THE PROB BEGAN SHORTLY AFTER ATC ISSUED APCH CLRNC FOR THE VOR APCH WITH INSTRUCTIONS TO DSND TO 3000 FT AND SLOW TO 90 KTS. CONDITIONS AT THAT TIME WERE VMC WITH ESTIMATED VISIBILITY OF 6 MI OR GREATER. SHORTLY AFTER THE APCH CLRNC WAS ISSUED (DURING THE LNDG CHKLIST); I NOTICED THAT THE REAR PAX WAS UNRESPONSIVE TO MY QUESTIONS REGARDING HIS SEATBELT AND GENERAL CONDITION. AS I ALLOWED THIS DISTR TO CONTINUE WITH SEVERAL CALLS WITH UNINTELLIGIBLE RESPONSES AND A SUBSEQUENT PHYSICAL CHK OF THE REAR PAX'S SEATBELT; I INADVERTENTLY DEVIATED FROM THE APCH COURSE AND DSNDED BELOW THE ASSIGNED ALT. DURING THIS TIME I WAS MANAGING THE FLT ALT BY VISUAL CUES IN VMC. I WAS ALERTED TO THE PROB BY ATC AND RECOGNIZED A FULL-SCALE DEFLECTION ON THE CDI. HAVING LOST SITUATIONAL AWARENESS OF THE PUBLISHED APCH I CONTINUED IN ERROR TO FLY A WESTERLY HDG (AWAY FROM VOR #2) WHICH IS ALSO THE MISSED APCH POINT. AT THIS TIME; I RECOGNIZED THAT I SHOULD HAVE TERMINATED THE APCH. IN FACT; ATC QUERIED ME ON MY ABILITY TO CONTINUE THE APCH. SINCE IT WAS VMC; I DIDN'T FEEL IT WAS NECESSARY OR EVEN POSSIBLE TO RE-ESTABLISH THE APCH AS PUBLISHED. AFTER RECEIVING VECTORS BACK TO THE ZZZ #1 BASE LEG; I NOTIFIED ATC THAT I HAD ZZZ IN VISUAL CONTACT. AT THIS POINT MY FRONT PAX BEGAN A DIALOGUE; WHICH BLOCKED INCOMING CALLS FROM ATC. AS PIC I DO RECOGNIZE THAT CTL OF THE ACFT IS MY PRIMARY RESPONSIBILITY. REGARDLESS OF VMC CONDITIONS; I SHOULD HAVE FLOWN THAT APCH WITH CAREFUL PRECISION AND COMPLETE SITUATIONAL AWARENESS. WHILE AT NO TIME DID I CONSIDER WE WERE IN ANY DANGER; I WAS CLEARLY REMISS IN THIS PROC. CONTRIBUTING HUMAN FACTORS INCLUDE THE LACK OF A COPLT WHO COULD OVERSEE CHALLENGED PAX.