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Evidence-based Practice and Quality Improvement

A simple technique to improve oxygenation and prevent severe desaturation in deeply sedated patients during colonoscopy


Cohen, S.; Barsoum, S.; Hunter, C.; Khan, A.; Tse, J.

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European Journal of Anaesthesiology (EJA): June 12th, 2010 - Volume 27 - Issue 47 - p 29
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Background and Goal of Study: A simple plastic sheet has been shown to convert a nasal cannula (NC) to a face tent at no cost.1–2 It improves oxygenation in deeply sedated patients during upper GI endoscopy.2 This technique has been used in our Endoscopy Suite. We wish to confirm its effectiveness in improving oxygenation while ascertaining FiO2 during colonoscopy.

Materials and Methods: This retrospective review of patients undergoing colonoscopy identified 2 groups. Group 1 received NC O2 (NC, n=59). Group 2 received NC O2 plus a face tent (FT, n=121) using a clear specimen bag (n=88) or a plastic shield (n=33).1–2 It covered the eyes, nose and mouth. Monitors included ECG, BP cuff, pulse oximetry and capnography+/−oximetry. Patients received NC O2 (3–5 l/min or higher as needed) and only iv propofol for sedation. Data collected for analysis included age, weight, height, room air (RA) O2 saturation (Sat), O2 Sat at 5-min intervals, the lowest O2 Sat, the need for assisted ventilation, the amount of propofol, O2 levels and the duration. Student's t-test and Chi Square test were used for analysis. A p value <0.05 was considered as significant. (Mean±S.D.)

Results and Discussion: There were no differences in age (NC: 56±16 yrs; FT: 57±14), BMI (NC: 27.1±4.1; FT: 27.6±5.8), ASA status (NC: 2.0±0.6; FT: 2.2±0.7), RA O2 Sat, the duration (NC: 26±13 min; FT: 28±12) and propofol dosages. There were significant differences in the highest O2 flow and O2 Sat after 5 min with O2, the lowest O2 Sat, severe O2 desaturation (Desat) (O2 Sat ≤ 85%) and the need for assisted ventilation between groups. Five NC patients experienced severe O2 Desat (O2 Sat: 82±12%) with sedation and O2 Sat was greatly improved to 99±1% after adding this face tent. FT patients (n=40) had high O2 levels (FiO2:68±14; FeO2:79±14%) with O2 flow at 4.4±0.8 l/min.

Table. Effec
Table. Effec:
ts of Face Tent on O2 Saturation during Colonscopy

Conclusion(s): Data show that this technique improves oxygenation, reduces severe desaturation and reduces the need for assisted ventilation in deeply sedated patients during colonoscopy. It increases O2 delivery without increasing O2 flow or cost.


1 Anesth 102:484, 2005.
#2. Anesth 107:A922, 2007.
© 2010 European Society of Anaesthesiology