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Expired gas backflow in oxygen delivery tubing
A J Coe1, M Wilson, N Maithani
1Hull and East Yorkshire NHS Trust, Castle Hill Hospital, Castle Hill, Cottingham, East Yorkshire, UK. andrew.coe@hey.nhs.uk
Expired gas can flow back into oxygen tubing during anaesthesia. To prevent contamination, single-use oxygen tubing is recommended, especially when patients cough or facemasks remain attached to disconnected oxygen sources.
Area of Science:
- Anesthesiology
- Respiratory Medicine
- Medical Device Safety
Background:
- Supplementary oxygen delivery via facemask is common during procedures like spinal anaesthesia.
- Potential for rebreathing or contamination of fresh gas supply exists with certain setups.
- Capnography is a valuable tool for monitoring respiratory gases.
Purpose of the Study:
- To investigate the extent of expired gas backflow into oxygen delivery tubing during supplementary oxygen administration.
- To assess the risk of contamination of the fresh gas outlet.
- To provide recommendations for safe oxygen delivery practices.
Main Methods:
- Capnography was used to detect carbon dioxide in oxygen tubing in sedated patients undergoing spinal anaesthesia.
- Measurements were taken at varying distances from the facemask and with different oxygen flow rates.
- Testing included scenarios with coughing and with the oxygen tubing disconnected from the source.
Main Results:
- Carbon dioxide was detected in oxygen tubing in 18% of patients upon coughing at 2 L/min oxygen flow.
- Expired gas was detected 1 meter from the facemask (fresh gas outlet) in 14 patients when the oxygen tubing was disconnected.
- No carbon dioxide was detected at the fresh gas outlet in a second group with flows of 2 and 4 L/min when facemasks were removed.
Conclusions:
- Detection of carbon dioxide suggests a risk of contamination of oxygen delivery systems.
- Strict single-use policy for oxygen tubing is advisable in this clinical setting.
- Filters may not be necessary if facemasks are removed when the fresh gas outlet is disconnected.
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