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October 17, 2009
2:00 PM - 4:00 PM
Room Area L
TSE "Mask" Reduces Desaturation in Sedated Patients by Increasing O 2 Delivery during Upper Endoscopy
  **   Shaul Cohen, M.D., Dora Zuker, M.D., Sachin Katyal, M.D., Dennis B. Hall, M.D., James Tse, M.D., Ph.D.
Anesthesia, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, New Jersey
Introduction: Patients usually receive O 2 via nasal cannula (NC) with iv sedation during upper GI endoscopy. Sedation and/or airway obstruction may cause severe O 2 desaturation. A simple plastic sheet (TSE "Mask") has been shown to improve oxygenation in sedated patients during upper endoscopy in a prospective study 1 . FiO 2 provided by this face tent was noted (range: 40-60%) 2 but not analyzed. We wished to review its effectiveness in improving oxygenation in sedated patients during upper endoscopy while ascertaining FiO 2 .

Methods: This is a retrospective review of patients undergoing EGD, EUS, ERCP, EGD/Colonoscopy or PEG. Monitors included ECG, BP cuff, pulse oximetry, capnography and oximetry (FiO 2 / FeO 2 ). Patients received O 2 via a Salter NC (3-5 l/min, or higher as needed). Group 1 patients (NC, n=67) received NC O 2 while Group 2 patients (TM, n=88) received NC O 2 and a TSE "Mask" from the beginning of the procedure. A TSE "Mask" was prepared using a clean plastic specimen bag (n=51) 1-3 or a plastic fluid-shield surgical mask (n=37) 3 . It covered the patient's eyes, nose and mouth. Patients were sedated with iv propofol. Attending anesthesiologists performed all anesthesia care. Data collected included age, weight, height, O 2 Sat, the need for assisted ventilation with an Ambu bag, the amount of propofol and the duration. FiO 2 , FeO 2 , ETCO 2 and inhaled CO 2 were measured via NC in TM patients. The Student t-test and the Chi Square test were used for statistical analysis. A p value <0.05 was considered as significant. (Mean±S.D.)

Results: There were no differences in age (NC 62±18; TM 60±16 yrs), BMI (NC 26±5; TM 27±7), ASA physical classification (NC 2.3±0.7; TM 2.4±0.8), RA O 2 Sat (NC 98±2%: TM 97±3%), the highest O 2 flow (NC 5.3±2.4; TM 5.0±1.4 l/min), the duration (NC 29±17; TM 31±19 min) and the overall dosages of propofol (NC 204±81; TM 208±90 ug/kg/min). There were significant differences in the lowest O 2 Sat (NC 90±10%; TM 96±5%), severe O 2 desaturation (O 2 Sat ≤85%) (NC 19/67; TM 1/88) and the need for assisted ventilation with an Ambu bag (NC 9/67; TM 0/88) between groups. In 19 NC patients, NCs were converted to TSE "Masks" during the procedure because of severe desaturation (Lowest O 2 Sat: 80±7%). With TM, their O 2 Sat was significantly improved at 5-min intervals (91±5%, 94±4%, 97±3%, 99±3%) and at the end of the procedure (99±1%). There was no difference in the lowest O 2 Sat between TM patients who received a plastic sheet (97±3%) and those who received a plastic shield (95±6%). The FeO 2 (67±14%) was significantly higher than FiO 2 (43±13%) in TM patients (n=41). There was a small amount of CO 2 rebreathing (inhaled CO 2: 4±3; ETCO 2 : 28±8 mm Hg) in TM patients (n=53).

Discussion: The data show that the TSE "Mask" increases O 2 delivery without increasing O 2 flow during upper endoscopy. However, the FeO 2 is 55% higher than FiO 2 . It indicates that sampling via a NC during inspiration underestimates O 2 delivery. The data also confirm that this simple plastic cover improves oxygenation, prevents severe O 2 desaturation and reduces the need for assisted ventilation in sedated patients during upper endoscopy. Even though this face tent could be used as a rescue device when patients' oxygenation deteriorates, we believe that it should be used prophylatically.

References: 1. Anesth 107:A922, 2007. 2. Anesth 102:484, 2005. 3.

From Proceedings of the 2009 Annual Meeting of the American Society Anesthesiologists.