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October 17, 2010
2:00:00 PM - 4:00:00 PM
Room Hall B1-Area O
TSE "Mask" Improves Oxygenation and Reduces Risk of Fire Hazard in Propofol-Sedated Obese Patients
  **   Niloufar Pourmasiha, D.O., Shaul Cohen, M.D., Julian Kertsman, M.D., Sylviana Barsoum, M.D., James Tse, Ph.D., M.D.
Anesthesia, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, New Jersey
Introduction: Desaturation (Desat) is common in obese patients under moderate-deep sedation. Raising nasal cannula (NC) O2 flow to improve oxygenation may increase risk of fire hazard.1 A plastic sheet has been shown to improve oxygenation in patients by converting NC to a face tent (TSE "Mask") at no cost.2-4 We wish to confirm its effectiveness in improving oxygenation in obese patients and assess O2 level under surgical drapes.

Methods: This retrospective review of patients undergoing various procedures (breast biopsy, AV fistula, cystoscopy, D & C, hysteroscopy, hernia repair) identified 2 groups. Group 1 received NC O2 (NC, n=46). Group 2 received NC O2 and a TSE "Mask" (TM, n=103) using a plastic specimen bag2-4 or a plastic fluid-shield surgical mask.4 It was taped along lower jaw and covered patient's mouth like a face tent. Monitors included ECG, BP cuff, pulse oximetry, capnography and oximetry. Patients received NC O2 (3-5 l/min) and iv propofol. Data collected included age, weight, height, O2 saturation (Sat), bag-mask ventilation, amount of propofol, procedure duration, FiO2 and O2 level under surgical drapes. Student's t-test and Chi Square test were used for analysis. A p value < 0.05 was considered as significant. (Mean±S.D.)

Among non-obese patients (BMI <30), there were no differences in age (NC: 52±17 yrs; TM: 54±19), BMI (NC: 24.3±3.4; TM: 24.6±3.2), ASA Physical status (ASA) (NC: 1.9±0.8; TM: 2.0±0.8), duration (NC: 39±22 min; TM: 50±29), propofol dose (NC: 155±76 ug/kg/min; TM: 178±77) and bag-mask ventilation (NC: 1/34; TM: 0/66). There were differences in room air (RA) O2 Sat (NC: 99±1%; TM: 98±2%), highest O2 flow (NC: 5.2±1.8 l/min; TM: 4.2±0.8), O2 Sat after 5 min with O2 (NC: 100±1%; TM: 100±0%), lowest O2 Sat (NC: 93±7%; TM: 98±3%) and severe Desat (O2 Sat <85%) (NC: 4/34; TM: 1/66).[figure1]Among obese patients (BMI>30), there were no differences in age (NC: 55±10 yrs; TM: 56±13), ASA (NC: 2.3±0.5; TM: 2.3±0.7), BMI (NC: 34.7±5.8; TM: 35.7±4.7), RA O2 Sat (NC: 97±2%; TM: 98±2%), duration (NC: 58±40 min; TM: 44±28), propofol dose (122±80 ug/kg/min; TM: 133±58) and bag-mask ventilation (NC: 2/12; TM: 1/37). There were differences in O2 Sat after 5 min with O2 (NC: 99±1%; TM: 100±0%), highest O2 flow (NC: 6.8±2.1 l/min; TM: 4.8±1.3), lowest O2 Sat (NC: 88±11%; TM: 97±3%) and severe Desat (O2 Sat <85%) (NC: 3/12; TM: 0/37).

TM group had higher FiO2 (60±18%) than NC (32±9%) and lower O2 level under surgical drapes (22±1%) than NC (41±13%).

Seven NC patients experienced severe Desat (83±10%) and were converted to TM. Their O2 Sat improved to 93±4%, 95±3% and 98±2% at 5-min intervals.

Discussion: The data show that TSE "Mask" improves oxygenation and prevents severe desaturation in propofol-sedated patients, especially in obese patients. It increases O2 delivery without raising O2 flow. It may improve patient safety and reduce risk of fire hazard by preventing O2 pooling under surgical drapes.

Ref: 1. J Anaesth Clin Pharm 22:199, 2006; 2. Anesth 102:484, 2005; 3. Anesth 107:A922, 2007; 4.

From Proceedings of the 2010 Annual Meeting of the American Society Anesthesiologists.
Figure 1