Supraglottic airways and oesophageal insufflation
This months anaesthesia journal reading revealed this gem from German authors.
In a cadaver model of simulated complete airway obstruction, ventilation pressures of 20mBar did not produce any oesophageal insufflation in any of the 4 supraglottic airways but at higher presssures 40mBar and greater, there was air leak into the oesophagus and this was more so in the laryngeal tube airway devices. iGel and LMA Supreme devices performed well.
Like Dr Levitan has always taught, low ventilation pressures using either manual BVM or a pressure limited ventilation mode are safest.
Br J Anaesth. 2012 Sep;109(3):454-8. Epub 2012 Jun 1.
Schmidbauer W, Genzwürker H, Ahlers O, Proquitte H, Kerner T.
Source
Department of Emergency Medicine, Bundeswehrkrankenhaus Berlin, Scharnhorststraße 13, 10115 Berlin, Germany.
Abstract
BACKGROUND:
Supraglottic airway devices (SADs) play an increasing role in airway management in clinical anaesthesia and emergency medicine. Until now, no data exist concerning the extent of oesophageal insufflation when oropharyngeal leak pressures are exceeded.
METHODS:
Laryngeal masks LMA-Supreme™ and LMA-ProSeal™, laryngeal tubes LTS-D and LTS II, Combitube™, and I-Gel were inserted into unfixed human cadavers. The oesophagus was connected to a volumeter, while the trachea was closed surgically to simulate complete airway obstruction. Volumes of oesophageal insufflation resulting from pressure-controlled ventilation at inspiratory pressures of 20, 40, and 60 mbar were measured.
RESULTS:
No oesophageal insufflation could be detected at a ventilation pressure of 20 mbar in any device. Using inspiratory pressures of 40 and 60 mbar, oesophageal insufflation occurred in all devices, with significantly higher volumes of intraoesophageal air for both laryngeal tubes.
CONCLUSIONS:
The use of SADs with inspiratory pressures of 20 mbar appears to be safe regarding the risk of intragastric insufflation. Higher inspiratory pressures should be strictly avoided.
Hi Minh,
Thanks for highlighting this article. I was surprised to read the authors claim that this aspect of SGAs has not previously been studied, but there you go.
20mBar = 15mmHg =2kPa. Worth knowing as the PEEP valve on our BVMs tightens up to a max of 20mmHg (26mBar).
Why do you think the devices with an oesophageal obturator balloon leaked more than the ones without (iGel, supreme)?
Matthew
I need a volunteer to test a theory around this..you care to donate your airway to science?
My theory is that these balloons do not seal as well as a cuffed mask but having said that the best performing device was the good ole Combitube! which has an oesophageal obturator balloon!
The paper does not discuss why the differences occurred between the devices but advises that if any of these devices are used then consideration of passage of a gastric drain be routinely performed
I think this also raises the point of using the older first generation supraglottic airways like the LMA classic..we should really be thinking about replacing them with second generation devices with gastric ports as this study suggests
I’ll have to “Fact or Crap” this article for you.