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.
Department of Emergency Medicine, Bundeswehrkrankenhaus Berlin, Scharnhorststraße 13, 10115 Berlin, Germany.
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.
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.
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.
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.