The influence of mouth opening on oropharyngeal leak pressure, intracuff pressure, and cuff position with the laryngeal mask airway

The Effects of Mouth Opening and Throat Pack Placement on Uncuffed Nasal Endotracheal Tube Leakage and Delivered Tidal Volumes in Mechanically Ventilated Pediatric Patients Undergoing Dental Procedures

Intubation for pediatric patients is frequently performed with an uncuffed endotracheal tube (ETT), which may result in an incomplete tracheal seal, resulting in gas leakage (leak). The purpose of this study was to assess the effect of (1) mouth opening and (2) throat pack placement in sealing and/or minimizing this leak to an acceptable level while providing adequate tidal volumes in mechanically ventilated patients. This prospective study of 2- to 6-year-olds undergoing general anesthesia with nasal intubation for dental procedures in the New York University-Lutheran Medical Center operating room was conducted between March 2015 and October 2015. Three sequential tidal volume (V_T) measurements were recorded: postintubation with the neck extended, with mouth opened, and after throat pack placement. Twenty-five subjects were included in the analyses. For subjects in whom no leak was detected, only throat pack placement statistically improved V_T. This is in marked contrast to numerically large, statistically significant effects, relative to baseline, for mouth opening (±23.2 mL, p < .009, 21% increase from baseline) and throat pack placement (±46 mL, p < .009, 41% increase from baseline) when a leak was detected. In children 2-6 years of age, nasal intubation with uncuffed ETTs that have incomplete tracheal seal have improved V_T with mouth opening and throat pack placement. This finding suggests that the intubation procedure is a process that extends through positioning, mouth opening, and throat pack placement.

Comparison of insertion of the modified i-gel airway for oral surgery with the LMA Flexible: a manikin study

We previously modified the i-gel airway to enable its use in the field of oral and maxillofacial surgery and reported its fabrication methods. In general, the standard i-gel airway is quick to insert and has a high success rate, but the modified i-gel airway has yet to be assessed for these attributes. We, therefore, set out to compare the ease of insertion of the modified i-gel airway with the LMA Flexible to investigate the usefulness of the modified i-gel airway. The study participants, who included 20 new interns with no experience using either the LMA Flexible or the modified i-gel airway, inserted each device 3 times into an intubation practice manikin. The variables measured in this study were insertion time and rate of successful insertions. Mean insertion time over 3 attempts was significantly shorter for the modified i-gel™ airway (18.9 ± 4.7 seconds) than the LMA Flexible (24.9 ± 5.1 seconds, P < .001). The rate of successful insertions as a total of all 3 attempts was significantly higher for the modified i-gel airway (56/60 times, 93.3%) than the LMA Flexible (45/60 times, 75%; P = .012). When used by an inexperienced operator, the modified i-gel™ airway is faster and has a higher success rate than the LMA Flexible, suggesting that it can be easily manipulated during insertion.

Effects of head-neck extension on abnormality of laryngeal mask airway function resulting from opening the mouth

PURPOSE

This study investigated the effects of head-neck extension on abnormalities of laryngeal mask airway (LMA) function resulting from opening the mouth.

PATIENTS AND METHODS

A single, experienced LMA user inserted the LMA in 15 patients scheduled for elective oral surgery. Oropharyngeal leak pressure and intracuff pressure were sequentially documented in 5 mouth conditions in order (0 minutes, mouth closed plus 0° extension; 3 minutes, mouth open plus 0° extension; 6 minutes, mouth open plus 15° extension; 9 minutes, mouth open plus 30° extension; and 12 minutes, mouth open plus 45° extension).

RESULTS

Oropharyngeal leak pressures with the mouth open plus 0° extension (30.7 ± 5.6 cm H(2)O, P < .001), mouth open plus 15° extension (29.1 ± 6.8 cm H(2)O, P < .001), and mouth open plus 30° extension (25.7 ± 6.1 cm H(2)O, P < .001) were significantly higher than with the mouth closed plus 0° extension (19.7 ± 2.8 cm H(2)O). Compared with the position with the mouth closed plus 0° extension (60.0 ± 0 cm H(2)O), intracuff pressures were also higher with the mouth open plus 0° extension (84.5 ± 14.1 cm H(2)O, P < .001), mouth open plus 15° extension (77.4 ± 11.0 cm H(2)O, P < .001), and mouth open plus 30° extension (73.6 ± 9.6 cm H(2)O, P < .001). Both measurement values returned to control levels when the position with the mouth open plus 45° extension was assumed (oropharyngeal leak pressure, 64.5 ± 6.5 cm H(2)O [P = .212]; intracuff pressure, 20.2 ± 4.9 cm H(2)O [P = .969]).

CONCLUSIONS

In procedures requiring the patient to have an open mouth under general anesthesia using LMA, 45° head-neck extension achieves acceptable airway conditions.

Optimal degree of mouth opening for laryngeal mask airway function during oral surgery

PURPOSE

This study was performed to determine the optimal degree of mouth opening in anesthetized patients requiring laryngeal mask airway (LMA) during oral surgery.

PATIENTS AND METHODS

A single, experienced LMA user inserted the LMA in 15 patients who were scheduled for elective oral surgery. Oropharyngeal leak pressure, intracuff pressure, and fiberoptic assessment of the LMA position were sequentially documented in 5 mouth conditions-opening of 1.4 (neutral position), 2, 3, 4, and 5 cm-and any resulting ventilatory difficulties were recorded.

RESULTS

Oropharyngeal leak pressure with the mouth open 4 cm (21.8 ± 3.2 cm H(2)O, P = .025) and 5 cm (27.3 ± 7.2 cm H(2)O, P < .001) was significantly higher than in the neutral position (18.1 ± 1.5 cm H(2)O), as was intracuff pressure (neutral position, 60.0 ± 0 cm H(2)O; 4 cm, 72.6 ± 5.1 cm H(2)O [P < .001]; and 5 cm, 86.9 ± 14.4 cm H(2)O [P < .001]). LMA position, observed by fiberoptic bronchoscopy, was unchanged by mouth opening, being similar in the 5 mouth conditions (P = .999). In addition, ventilation difficulties (abnormal capnograph curves or inadequate tidal volume) occurred in 2 of 15 patients (13%) and 7 of 15 patients (53%) (P < .001) with the mouth opening of 4 and 5 cm, respectively.

CONCLUSIONS

This study showed that a mouth opening over 4 cm led to substantial increases in oropharyngeal leak pressure and intracuff pressure of the LMA, warranting caution, because gastric insufflation, sore throat, and ventilation difficulties may occur. A mouth opening of 3 cm achieves acceptable airway conditions for anesthetized patients requiring LMA.