Question: Is there a billable code for monitoring oxygen and heart function during vein surgery (endovenous ablation)? The physician performs the procedure in an office setting and bills 36478, 36479, and/or 36470. Washington Subscriber Answer: Monitoring the patient’s oxygen, heart rate, and blood pressure is always included in the scope of the main procedure. If you’re billing for the anesthesiologist’s service, only report the applicable anesthesia code and the associated time units.