Laryngopharyngeal pH measurement

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Most emergency department (ED) intubations are to prevent gastric contents aspiration. The incidence of aspiration is unknown and intubation has complications. Balancing these risks requires an idea of the incidence of aspiration. This study assessed one technique for investigating the aspiration risk in ED patients. Cricoid pressure is used to reduce this risk and the technique may also examine this manoeuvre.


Cohorts of unconscious adult ED and elective surgical patients were recruited. The posterior pharyngeal wall pH was measured immediately before and after intubation. Pharyngeal pH was used to indicate risk of aspiration, and pH change to assess the efficacy of cricoid pressure.


Eight ED and 48 control patients were recruited. In the ED cohort, pH ranged from 6.0 to 8.0 before intubation and 4.7 to 8.0 after intubation: a mean decrease of 0.3 (95% CI 1.5 decrease to 0.9 increase). In the control cohort pH ranged from 5.8 to 8.0 before intubation and 6.0 to 8.0 after intubation: a mean increase of 0.4 (95% CI 0.1 to 0.6 increase).


This is a simple, cheap, and repeatable technique for assessing aspiration risk in emergency intubations. A larger study is required to assess the efficacy of cricoid pressure.

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