The intubating laryngeal mask airway: effect of handle elevation on efficacy of seal, fibreoptic position, blind intubation and airway protection

Effectiveness of Intubating Laryngeal Mask Airway in managing out-of-hospital cardiac arrest by non-physicians

AIM OF THE STUDY

The role of supraglottic devices in airway management in out-of-hospital cardiac arrest (OHCA) remains controversial. The aim of this study was to evaluate the feasibility and effectiveness of intubation through the Intubating Laryngeal Mask Airway (ILMA) when used by prehospital emergency nurses in the setting of OHCA.

METHODS

We conducted a prospective, observational trial during 12 years by the Fire Department and prehospital emergency service of the health district of Strasbourg, France. The primary outcome was the success rate of ventilation after intubation through the ILMA, while the secondary outcomes were the success rate of ventilation after insertion of the ILMA and complications related to ILMA placement and intubation. Factors associated with successful intubation were also studied.

RESULTS

During the study period, 1464 ILMA placements were attempted by emergency nurses during OHCA. Ventilation was possible in 1250 patients (85.38%) after ILMA placement and in 1078 patients (73.63%) after intubation. Regurgitation of gastric contents occurred in 237 (16.18%) patients, mostly during basic life support. Two factors were predictive of a successful tracheal intubation: the performance of the Chandy maneuver OR = 2.91 (CI: 2.07-3.97) and the number of attempts at intubation OR = 1.95 (CI: 1.43-2.61). Conversely, the number of attempts at ILMA insertion was predictive of an intubation failure OR = 0.11 (CI: 0.07-0.17).

CONCLUSION

The success rate of intubation through the ILMA was high. After ILMA placement, ventilation was possible in 1250 patients (85.38%) and in 1078 patients (73.63%) after intubation.

Overinflation of the cuff and pressure on the neck reduce the preventive effect of supraglottic airways on pulmonary aspiration: an experimental study in human cadavers

BACKGROUND

The oesophageal leak pressure is defined as the pressure which breaks the seal between the cuff of a supraglottic airway and the peri-cuff mucosa, allowing penetration of fluid into the pharynx and the oral cavity. As a consequence, a decrease in this variable increases the risk of reflux and can lead to pulmonary aspiration. The aim of this study was to analyse the effects of cuff overinflation and pressure on the neck on the oesophageal leak pressure of seven supraglottic airways.

METHODS

Three laryngeal masks, two laryngeal tubes, and two oesophageal-tracheal tubes were tested in an experimental setting. In five human cadavers, we simulated a sudden increase in oesophageal pressure. To measure baseline values (control), we used an intracuff pressure as recommended by the manufacturer. The first intervention included overinflation of the cuff by applying twice the amount of pressure recommended. A second intervention was defined as external pressure on the neck.

RESULTS

The oesophageal leak pressure was decreased for laryngeal masks (control, 28 cm H2O; overinflation, 9 cm H2O; pressure on the neck, 8 cm H2O; P<0.01) and for laryngeal tubes (control, 68 cm H2O; overinflation, 37 cm H2O; pressure on the neck, 39 cm H2O; P<0.01) and was unaffected for oesophageal-tracheal tubes (control, 126 cm H2O; overinflation/pressure on the neck, 130 cm H2O; n.s.).

CONCLUSION

Cuff overinflation and pressure on the neck can enhance the risk of gastro-oesophageal reflux when using supraglottic airways. Therefore, both manoeuvres should be avoided in clinical practice.

Intubating laryngeal mask airway

The Intubating Laryngeal Mask Airway (ILMA) was introduced into clinical practice in 1997 following numerous clinical trials involving 1110 patients. The success rate of blind intubation via the device after two attempts is 88% in "routine" cases. Successful intubation in a variety of difficult airway scenarios, including awake intubation, has been described, with the overall success rate in the 377 patients reported being approximately 98%. The use of the ILMA by the novice operator has also been investigated with conflicting reports as to its suitability for emergency intubation in this setting. Blind versus visualized intubation techniques have also been investigated. These techniques may provide some benefits in improved safety and success rates, although the evidence is not definitive. The use of a visualizing technique is recommended, especially whilst experience with intubation via the ILMA is being gained. The risk of oesophageal intubation is reported as 5% and one death has been described secondary to the complications of oesophageal perforation during blind intubation. Morbidity described with the use of the ILMA includes sore throat, hoarse voice and epiglottic oedema. Haemodynamic changes associated with intubation via the ILMA are of minimal clinical consequence. The ILMA is a valuable adjunct to the airway management armamentarium, especially in cases of difficult airway management. Success with the device is more likely if the head of the patient is maintained in the neutral position, when the operator has practised at least 20 previous insertions and when the accompanying lubricated armoured tube is used.

ProSeal versus the Classic laryngeal mask airway for positive pressure ventilation during laparoscopic cholecystectomy

BACKGROUND

We tested the hypothesis that the ProSeal laryngeal mask airway (PLMA) is a more effective ventilatory device than the Classic laryngeal mask airway (LMA) for laparoscopic cholecystectomy.

METHODS

Eighty anaesthetized, paralyzed patients (ASA 1-2, aged 18-80 yr) were randomly allocated for airway management with the PLMA or LMA. Ease of insertion and efficacy of seal were determined. Peak airway pressures were recorded immediately before and after carboperitoneum to 2.0 kPa. The inspired oxygen concentration and/or the ventilatory variable were adjusted according to a protocol to maintain SpO2 > or = 95% and E'CO2 < 6.0 kPa. Oxygenation was considered suboptimal if SpO2 fell to 94-90% and failed if SpO2 was < 90%. Ventilation was considered suboptimal if E'CO2 was > 6.0-7.3 kPa and failed if E'CO2 was > 7.3 kPa.

RESULTS

First-time insertion success rates were higher for the LMA (40/40 vs 33/40; P = 0.02). Seven patients required two attempts with the PLMA. Oropharyngeal leak pressure was higher for the PLMA [29 (SD 6) vs 19 (4) cm H2O; P < 0.001]. There was a similar, significant increase in peak airway pressure after carboperitoneum for both devices (P < 0.001). Before carboperitoneum, oxygenation and ventilation were optimal in all patients in both groups. After carboperitoneum, oxygenation was optimal in all patients in both groups, but ventilation was suboptimal more frequently with the LMA (8 vs 0; P = 0.01). In three of these eight patients, ventilation failed but was subsequently optimal with the PLMA.

CONCLUSION

The PLMA is a more effective ventilatory device for laparoscopic cholecystectomy than the LMA. We do not recommend the use of the LMA for laparoscopic cholecystectomy.

Intubating laryngeal mask airway size selection: a randomized triple crossover study in paralyzed, anesthetized male and female adult patients

We determined the optimal size of intubating laryngeal mask airway (ILM) for ventilation and blind tracheal intubation in men and women. We also determined the distance the tracheal tube needs to protrude beyond the distal aperture to ensure that the cuff is through the vocal cords. Fifty male and 50 female anesthetized, paralyzed patients (ASA physical status I or II, aged 18-80 yr) were studied. Three operators (A, B, and C) were involved for the purposes of blinding. The size 3, 4, or 5 ILM was inserted into each patient in random order by Operator A, and the quality of ventilation was scored (adequate, suboptimal, or failed) by Operator B. The fiberoptic position (correct, too shallow, or too deep) and the distance between the distal aperture and the vocal cords was determined by Operator B. A single attempt at blind intubation was made by Operator C. Operators B and C were blinded to the size of the ILM. Operator C was also blinded to the information recorded by Operator B. All ILMs were inserted into the laryngopharynx at the first attempt. For men and women, the ventilation score was smaller for the Size 3 than the Size 4 or 5 (all: P < 0.002). For men, correct positioning was less common with the Size 3 than the Size 4 or 5 (both: P < 0.02). For women, correct positioning was similar among sizes. For men, tracheal intubation was successful less frequently with the Size 3 (84%) than the Size 4 (100%) or 5 (98%) (both: P < or = 0.01). For women, tracheal intubation success was similar among sizes (Size 3, 4, and 5: 86%, 96%, and 92%, respectively). Intubation was always successful if the ILM was correctly positioned and always failed if it was too shallow or deep. In both male and female patients, the distance between the distal aperture and the vocal cords increased with increasing ILM size (all: P < 0.04) and patient height (P < 0.0001) and was always longer for men (all: P < 0.0001). The overall mean distance (95% confidence interval) that the tracheal tube needed to protrude was 10-12 cm (8-13 cm) in men and 8-11 cm (8-12 cm) in women. We conclude that for men, the Size 4 and 5 ILMs are better than the Size 3 for ventilation and blind intubation. For women, the Size 4 and 5 ILMs are better than the Size 3 for ventilation, but there is no difference among sizes for blind intubation. The length the tracheal tube must protrude from the distal aperture to ensure that the cuff is completely through the vocal cords is 8-13 cm, depending on ILM size, the tracheal tube size, and the sex and height of the patient.

IMPLICATIONS

For men, the Size 4 and 5 intubating laryngeal mask airways are better than the Size 3 for ventilation and blind tracheal intubation. For women, the Size 4 and 5 are better than the Size 3 for ventilation, but there is no difference among sizes for blind intubation. The length the tracheal tube must protrude from the distal aperture of the intubating laryngeal mask airway to ensure that the cuff is completely through the vocal cords is 8-13 cm, depending on the size of the mask and tracheal tube and on the sex and height of the patient.