Clinical Evaluation of the Cricoid Pressure Effect on Bag Mask Ventilation, ProSeal Laryngeal Mask Airway Placement and Ventilation

Objective: Supraglottic airway devices can be life-saving in the 'cannot intubate, cannot oxygenate' situation. The cricoid pressure (CP) is considered critical in the prevention of aspiration. The aim of this self-controlled study was to evaluate the effect of CP on the bag mask ventilation (BMV), and the placement of and the ventilation through, the ProSeal laryngeal mask airway (LMA). Methods: In 60 adult patients undergoing elective surgery, after induction of anaesthesia, the effect of bimanual CP (approximate to 30N) on BMV, ventilation through the ProSeal LMA, its anatomic position and airway seal pressures were evaluated. CP was released, the ProSeal LMA was reseated (appropriate position), the above assessments were repeated, and the effect of CP on the tidal volume (TV) and peak inspiratory pressure (PIP) was noted. Results: Out of 60 patients, the bag mask ventilation with CP was adequate in 25 (41.7%) patients compared to 59 (98.3%) patients without CP; p<0.001. The ventilation via the ProSeal LMA with CP was excellent, adequate and impossible in 0.0% (0), 49.2% (29) and 50.8% (30) patients, respectively, compared to 93.3% (56), 6.7% (4), 0% (0) patients, respectively, without CP; p<0.001. Releasing CP and advancing the ProSeal LMA to its appropriate position significantly improved the ventilation and anatomic position scores; both p<0.001. Airway seal pressures improved significantly without CP compared to with CP; p<0.001). With the ProSeal LMA in a proper position, the CP application resulted in a significant decrease in the mean expired TV (489.14 +/- 91.62 vs. 355.08 +/- 104.42 mL) with an increase in PIP (16.72 +/- 5.01 vs. 30.71 +/- 6.74 cmH2O); both p<0.001. Conclusion: The application of bimanual CP (approximate to 30N) interferes with the bag mask ventilation and prevents both the correct placement and ventilation via the ProSeal LMA in adult patients.