The investigators data reveal an important new observation regarding the recovery of breathing during emergence from general anesthesia: respiration resumes as a prolonged abdominal expiration event.

The present study aims to further clarify the physiology of recovery of breathing with the addition of a cutaneous monitor for arterial carbon dioxide measurement and a comparison of two different recovery paradigms.

The present study will use non-invasive respiratory inductance plethysmography(RIP) and transcutaneous carbon dioxide measurement to compare recovery of respiration under constant Transcutaneous carbon dioxide measurement( ptcCO2) with continuous high frequency jet ventilation HFJV (study method) with recovery of respiration during rising and apnea (current standard).

The investigators hypothesize that the prolonged abdominal expiration that we observed during recovery of breathing in prior studies will be unaffected by arterial carbon dioxide (CO2) levels.

Inclusion Criteria:

1. Male or Female patients ages > 18 to < 80
2. Scheduled for procedures under general anesthesia with jet ventilation
3. Sign informed consent
4. Candidate for total intravenous anesthesia with propofol and remifentanil (which is standard protocol in this type of population)

Exclusion Criteria:

1. Absence of informed consent
2. No planned use intra-operative use of jet ventilation
3. Known difficulties with jet ventilation during prior surgical procedures
4. Emergency surgery
5. Baseline (oxygen saturation)SpO2 <92% on room air
6. BMI > 50
7. Pregnant or lactating females
8. Skin damage, rash or significant lesions in the areas covered by the RIP bands or transcutaneous CO2 sensor.