[Influence of pressure on cricoid on insertion ProSeal laryngeal mask airway and ventilation function]

To assess the influence of cricoid pressure (CP) on insertion and ventilation function of ProSeal laryngeal mask airway (PLMA).

Fifty adult patients with American Society of Anesthesiologists (ASA) physical status category I, scheduled for elective plastic surgery were studied. After induction of intravenous anesthesia, the PLMA was inserted using an introducer under CP and the intracuff pressure was set to 60 cm H(2)O (1 cm H(2)O=0.098 kPa) with the introducer in place. The content degree of lung ventilation, airway seal pressure and anatomic position of the cuff were assessed. Then CP was temporary terminated, the PLMA was further advanced to the ideal position and the intracuff pressure was readjusted to 60 cm H(2)O. The above-mentioned assessments were re-performed, and the expiratory tidal volume and peak inspiratory pressure during positive-pressure ventilation (PPV) with and without CP were recorded. The gastric tube placement through the PLMA was observed, anatomical position of the drain tube was also scored by fiberoptic examination.

After the PLMA was further advanced to the ideal position under temporary termination of CP, lung ventilation content degree (good: acceptable=50:14 cases), airway seal pressure [(27+/-7) cm H(2)O vs. (21+/-7) cm H(2)O] and fiberoptic score of anatomical position of cuff were significantly improved compared with those after PLMA insertion under CP (P<0.05). The expiratory tidal volume during PPV was not significantly different between with and without CP, but the peak inspiratory pressure increased from (14+/-2) cm H(2)O without CP to (28+/-5) cm H(2)O with CP, and there was statistically significant difference (P<0.05). In all patients, gastric tube placement through the PLMA was successful with single attempt and correct anatomical position of the drain tube was confirmed by fiberoptic examination.

The CP can impede the insertion of PLMA into the ideal position. The PLMA is still able to be advanced to the ideal position with a special introducer under temporary termination of CP. After the PLMA is advanced to the ideal position, the CP produces a significant increase in the peak inspiratory pressure during PPV.