G0500 HCPCS - MODERATE SEDATION SERVICES PROVIDED BY THE SAME PHYSICIAN OR OTHER QUALIFIED HEALTH CARE PROFESSIONAL PERFORMING A GASTROINTESTINAL ENDOSCOPIC SERVICE THAT SEDATION SUPPORTS, REQUIRING THE PRESENCE OF AN INDEPENDENT TRAINED OBSERVER TO ASSIST IN THE MONITORING OF THE PATIENT'S LEVEL OF CONSCIOUSNESS AND PHYSIOLOGICAL STATUS; INITIAL 15 MINUTES OF INTRA-SERVICE TIME; PATIENT AGE 5 YEARS OR OLDER (ADDITIONAL TIME MAY BE REPORTED WITH 99153, AS APPROPRIATE)