To explore the effectiveness of transcutaneous acupuncture electrical stimulation (TAES), a non-invasive modality in improvement of the function of respiration and circulation on elder patient during colonoscopy.

To assess the function of respiratory and circulation before precondition, during colonoscopy and end of the procedure, blood cortisol and catecholamine levels were measured also.The incidence of airway support, application of vasoactive drug or atropine during procedure were recorded in the meantime.

Inclusion Criteria:

1. patients aged 65 or older
2. American Society of Anesthesiologists (ASA) grade I~II
3. consent and voluntary participation in this experiment
4. patients under colonoscopy
5. none allergic to propofol and fentanyl
6. airway assessment for none difficult airway

Exclusion Criteria:

1. Allergic to propofol, fentanyl.
2. ASA is greater than or equal to grade 3
3. Abnormal respiratory tract may cause severe respiratory obstruction
4. unsatisfactory control of hypertension, systolic pressure over 160 millimeter of mercury (mmHg) or diastolic pressure over 100 mmHg
5. Hypotension, systolic pressure below 90 mmHg, heart rate (HR) <50bpm or >100bpm