To the Editor:
We were keen to read the authors study testing the use of second generation supraglottic airway devices(SAD) to prevent aerosol generation during cardiopulmonary resuscitation(CPR)1. We commend the authors for undertaking this timely study however we have some concerns with their results.
The authors placed six different SAD in an Airman simulator (Laerdal, Norway). In their methods, the authors do not state how they determined that the SADs were appropriately sized and placed. Visualization with a fiberoptic bronchoscope would have been the best method to confirm correct positioning2. There is also evidence that the seal of a supraglottic airway differs based on the material (plastic vs. silicone) used in the construction of a mannequin3 and is different between a mannequin and a human. This may make the findings from this report not be applicable to clinical practice.
The authors mention that they inflated the cuff of the supraglottic airway to 80 cm of water, which is 20 cm of water above the manufacturer's pressure, to improve the seal of the supraglottic airway. There is evidence to suggest that the best seal may be obtained in humans at pressures of one-third to two-thirds of the maximum recommended inflation pressures, and over-inflating may actually make the cuff more rigid and increase the leak around the supraglottic airway4. Did the authors quantify the positive pressure at which leak occurred with each SGA? This alone may explain the authors results. In addition, the findings of this mannequin study differ from that of a cadaver study, which found no aerosol spread with CPR when similar supraglottic airways with a filter were in place5. The implications of the conclusion regarding aerosol generation during CPR with a well placed second generation supraglottic airway needs to be placed in the context of the limitations associated with a mannequin-based study.
Conflict of interest
Pete Kovatsis is a Medical editor for Verathon Inc., USA; Pete Kovatsis has a patent pending for an intubation shield.
References
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