Related Experiment Video
Updated: Jul 19, 2026

Design and Development of a Model to Study the Effect of Supplemental Oxygen on the Cystic Fibrosis Airway Microbiome
Published on: August 3, 2021
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
Abstract:
Using capnography, we investigated the backflow of expired gas into oxygen delivery tubing in 18 sedated patients receiving supplementary oxygen via a disposable facemask during spinal anaesthesia. At 5 cm from the mask, with an oxygen flow of 2 l.min(-1), carbon dioxide was detected in the oxygen delivery tubing of three patients (18%) on coughing. With the patient wearing the facemask but the oxygen tubing disconnected from the oxygen source, carbon dioxide was detectable 1 m from the facemask (i.e. at the fresh gas outlet) in 14 patients. In a second group of 20 similar patients, no carbon dioxide was detected sampling at the fresh gas outlet with flows of 2 and 4 l.min(-1). Assuming that detection of carbon dioxide indicates at least the possibility of contamination, oxygen tubing should be strictly single-use in this setting. Our findings suggest that filters are not required to protect gas supply outlets, provided that the patient's facemask is removed when the fresh gas outlet is disconnected.
More Related Videos
Related Concept Videos
Oxygen Delivering System II: Venturi Mask and Transtracheal Oxygen
Venturi Mask
The Venturi mask, named after the Venturi effect, is designed to deliver precise oxygen concentrations. It consists of a large tube with an oxygen inlet that narrows down, causing a pressure drop that pulls air in through adjustable side ports. The mask is a lightweight,...
Oxygen Delivering System III: Tracheostomy and T-piece
Tracheostomy
A tracheostomy is a surgically created opening (stoma) in the anterior part of the trachea. It is used to establish a patient airway, bypass an upper airway obstruction, simplify the removal of secretions, permit long-term...
Oxygen Delivering System I: Nasal Cannula and Face Mask
Nasal Cannula
A nasal cannula is a lightweight tube split at one end into two prongs and placed in the nostrils. It is typically used to deliver low to medium levels of oxygen.
Suggested flow rate: The suggested flow rate for a nasal cannula typically ranges between 1 and 6 L/min.
Oxygen percentage setting:...
Administering Oxygen by Mask
Administering oxygen by mask is a common nursing intervention that provides supplemental oxygen to patients with respiratory distress or chronic lung conditions. This procedure involves delivering oxygen at a specified rate through a face mask connected to an oxygen source.
Equipment
The equipment necessary for this procedure includes:
Gas Exchange and Transport
Administering Oxygen by Nasal Cannula
Nasal Cannulas
A nasal cannula is a lightweight tube split into two prongs placed in the nostrils, connected...

