With regards to the endotracheal  tube pictured below, what is the purpose of the lumen labelled A

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College Answer

With regards to the endotracheal  tube pictured below, what is the purpose of the lumen labelled A

Suction  port  with  aperture  above  the  cuff  enables   continuous   suction  of  subglottic secretions which and thus may limit nosocomial pneumonia occurring as a consequence of aspiration.

Discussion

 The endotracheal tube is discussed in detail elsewhere.

This added supraglottic port enables the aspiration of secretions which collect above the tube cuff. According to a review of the available evidence in Revista Brasileira de Terapia Intensiva one should not expect very much improvement in mortality or duration of ventilation. The risk of VAP is somewhat reduced.

The disadvantage of suctioning above the cuff is mucosal damage. The sucker applies 100mmHg pressure to the tracheal wall. This sort of pressure- though considered "low wall suction" - can still strip mucosa off the walls of the trachea. This, it seems, is predominantly a risk associated with continuous rather than intermittent subglottic suction.

References

References

Souza, Carolina Ramos de, and Vivian Taciana Simioni Santana. "Impact of supra-cuff suction on ventilator-associated pneumonia prevention." Revista brasileira de terapia intensiva 24.4 (2012): 401-406.

DePew, Charlotte L., and Mary S. McCarthy. "Subglottic secretion drainage: a literature review." AACN advanced critical care 18.4 (2007): 366-379.