Cricoid pressure impedes placement of the laryngeal mask airway and subsequent tracheal intubation through the mask.

We have studied 40 patients to see if cricoid pressure affects the success rate of ventilation through, and the position of, the laryngeal mask and subsequent fiberscope-aided tracheal intubation. Adequate ventilation of the lungs was produced through the laryngeal mask in 19 of 20 patients in the control group, but in only 10 of 20 patients in the cricoid pressure group (P < 0.002). The laryngeal mask was positioned correctly in 16 patients in the control group, but in only two patients in the cricoid pressure group (P < 0.001). Tracheal intubation was accomplished in 19 patients in the control group, but in only three patients in the cricoid pressure group (P < 0.001). Release of cricoid pressure after placement of the laryngeal mask improved the view of the glottis, but tracheal intubation was still difficult because of laryngeal deviation. These results show that cricoid pressure impedes placement of the laryngeal mask and subsequent fiberscope-aided tracheal intubation.