What effect does intubation have on regional lung ventilation?
Research type
Research Study
Full title
Observational study of the effect of tracheal intubation and tracheal tube position on regional lung ventilation during general anaesthesia.
IRAS ID
230517
Contact name
Andrew Lumb
Contact email
Sponsor organisation
Leeds Teaching Hospitals Trust
Duration of Study in the UK
0 years, 3 months, 31 days
Research summary
Research Summary:
During any general anaesthetic which involves muscle relaxation artificial breathing is required. This is most commonly provided by pushing air under pressure (positive pressure ventilation) into the lungs via a tube in the airway (the tracheal tube). It has been observed for many years that with this form of breathing the distribution of gas within the lungs differs from that seen during ‘natural’ breathing: more of the gas goes to the upper parts of the lung than lower parts. This change in how the gas is distributed can lead to problems with how well oxygen is taken up by blood and carbon dioxide removed from the body.
Previous work using mathematical modelling has found that the position of the tracheal tube might affect air distribution, but this has previously been difficult to study in ‘real life’, requiring the use of radioactive dyes and computerised tomography (CT). However a bedside test is now available which allows us to study these changes rapidly and non-invasively, using electrical impedance tomography (EIT). The EIT device is commercially available (PulmoVista®, Draeger UK) and is used in hospitals worldwide as a bedside monitor of lung ventilation.
This study aims to investigate the effect of tracheal intubation on regional ventilation of the lungs by comparing measurements before and after the patient is anaesthetised and intubated. We aim to show whether altered patterns of ventilation are caused by patients simply being asleep and ventilated, or whether these changes are due to the use of a tracheal tube itself. The exact effect of tube position will also be studied by measuring ventilation as the tube is deliberately advanced until it enters one of the lungs. This will give us information about the ideal position for a tube within the trachea to promote optimal ventilation patterns within the lungs.Lay summary of study results: Anaesthesia and artificial ventilation cause changes to how gas is distributed throughout the lung due to the airway tube used during anaesthesia. We used a technique called electrical impedance tomography to map gas distribution during anaesthesia in ten patients with and without an airway tube.
We recorded data in subjects who were awake, during bag-mask ventilation when anaesthetized but with no airway tube in place, and with the airway tube positioned normally, rotated 90° to each side and advanced until it was too far into the lung. Relative to subjects who were awake, anaesthesia with bag-mask ventilation reduced gas flow to the right lung and increased gas flow to the front of the lungs. Ventilation through a tube caused further changes to gas distribution, particularly when the tube was near the carina where the airway divides into left and right lungs. Rotating the tube to one side slightly improved gas flow to the right lung but gas distribution remained abnormal. These results suggest that even ideal tube positioning during general anaesthesia cannot avoid the changes in gas distribution seen in the lungs compared with when awake.REC name
Yorkshire & The Humber - South Yorkshire Research Ethics Committee
REC reference
17/YH/0319
Date of REC Opinion
19 Oct 2017
REC opinion
Further Information Favourable Opinion