LMA--reduction of gas leak

Lightwand-Guided Insertion of Flexible Reinforced Laryngeal Mask Airway: Comparison with Standard Digital Manipulation Insertion

Background

The flexibility of the long flexometallic tube makes insertion of the flexible reinforced laryngeal mask airway (f-LMA) difficult. We compared the usefulness of rigid lightwand-guided f-LMA insertion with standard digital manipulation.

Material/Methods

Fifty-four patients (aged 19–70 years) were randomly divided into a control group (digital manipulation technique) or the lightwand group (lightwand-guided insertion technique). The insertion profiles, oropharyngeal leak pressure (OLP), peak inspiratory pressure (PIP), expiratory tidal volume, and ventilatory score were measured in patients with neutral, extension, rotation, flexion, and re-neutral head-neck positions in turn.

Results

The success rate and ease of insertion did not differ between groups, but the insertion time was longer in the lightwand group. The fiberoptic laryngeal view was significantly better in the lightwand group than in the control group. However, the OLP, PIP, expiratory tidal volume, and ventilatory scores were not significantly different between groups according to head-neck positions. The extension posture was associated with a significant negative effect on ventilation, but ventilation returned to initial levels with the other postures.

Conclusions

Lightwand-guided f-LMA insertion showed a better fiberoptic laryngeal view than standard digital manipulation, but no improvement in the ventilatory state was observed due to position. Therefore, lightwand-guided insertion could facilitate correct placement of the f-LMA, but it has limited clinical usefulness.

Comparison of the ProSeal laryngeal mask airway with the I-Gel™ in the different head-and-neck positions in anaesthetised paralysed children: A randomised controlled trial

Background and Aims:

Head and neck movements alter the shape of the pharynx, resulting in changes in the oropharyngeal leaking pressures and ventilation with supragottic airway devices. We compared the effect of the different head-and-neck positions on the oropharyngeal leak pressures and ventilation with the I-Gel™ and ProSeal™ laryngeal mask airway (PLMA) in anaesthetised paralysed children.

Methods:

A total of 70 children were randomly assigned to receive PLMA (n = 35) or I-Gel™ (n = 35) for airway management. Oropharyngeal leak pressure in maximum flexion, maximum extension and the neutral position was taken as the primary outcome. Peak inspiratory pressures (PIPs), expired tidal volume, ventilation score and fibreoptic grading were also assessed.

Results:

No significant difference was noted in oropharyngeal leak pressures of PLMA and I-Gel™ during neutral (P = 0.34), flexion (P = 0.46) or extension (P = 0.18). PIPs mean (standard deviation [SD]) were significantly higher (17.7 [4.03] vs. 14.6 [2.4] cm H₂O, P = 0.002) and expired tidal volume mean [SD] was significantly lower (5.5 [1.6] vs. 6.9 [2] ml/kg, P = 0.0017) with I-Gel™ compared to PLMA. Fibreoptic grading and ventilation score were comparable in both the groups in all the three head-and-neck positions.

Conclusion:

PLMA and I-Gel™, both recorded similar oropharyngeal leaking pressures in all the three head-and-neck positions. However, higher peak pressures and lower expired tidal volume in maximum flexion of the neck while ventilating with I-Gel may warrant caution and future evaluation.

Comparison of i-gel™ and Laryngeal Mask Airway Supreme™ in Different Head and Neck Positions in Spontaneously Breathing Pediatric Population

BACKGROUND

Although the advantages of ventilation with i-gel™ and laryngeal mask airway Supreme (LMA-Supreme™) has been well documented, they are still under debate for surgeries requiring flexion and extension of neck such as thyroid surgery, tonsillectomy, and neck exploration. Hence, we conducted a study to demonstrate the effect of neck flexion and extension in spontaneously breathing anesthetized pediatric patients utilizing i-gel™ and LMA-Supreme™.

METHODS

A prospective, randomized comparative study was conducted on sixty children, thirty each in i-gel™ and LMA-Supreme™ group. Oropharyngeal leak pressure (OPLP), fiberoptic view of vocal cords, and exhaled tidal volume were evaluated in neutral, flexion, and extension neck positions in spontaneously breathing children.

RESULTS

OPLP for i-gel™ was found to be significantly higher in flexion (29.00 ± 1.95 cmH₂O, P < 0.001) and lower in extension (21.07 ± 2.08 cmH₂O, P < 0.001) as compared to neutral (24.67 ± 2.08 cmH₂O). Similar results were observed for LMA-Supreme™ which showed significantly higher OPLP in flexion (24.73 ± 2.26, P < 0.001 respectively) and lower in extension (18.67 ± 1.42 cmH₂O, P < 0.001) as compared to neutral (20.87 ± 1.80 cmH₂O). Worsening of fiberoptic view occurs for i-gel™ and LMA-Supreme™ in flexion (10/12/5/3/0 and 11/14/2/2/1, P < 0.05) as compared to neutral position (17/10/2/1/0 and 15/12/1/1/1), respectively. Significant change did not occur in extension. Ventilation worsening occurred in flexion as compared to neutral position evidenced by significant decrease in exhaled tidal volume (92.90 ± 11.42 and 94.13 ± 7.75 ml, P < 0.05) as compared to neutral (100.23 ± 12.31 and 101.50 ± 8.26 ml) for i-gel™ and LMA-Supreme™, respectively.

CONCLUSION

Neck flexion caused a significant increase in leak pressure in both i-gel™ and LMA-Supreme™. With deterioration of fiberoptic view and ventilation, both devices should be used cautiously in pediatric patients in extreme flexion.

Evaluation of I-Gel™ size 2 airway in different degrees of neck flexion in anesthetized children - a prospective, self-controlled trial

BACKGROUND

A previous study by our group demonstrated an increase in oropharyngeal leak pressures and a deterioration of ventilation in maximum neck flexion with the I-Gel^™ . To ascertain the optimal degree of neck flexion which increases OPLP without compromising ventilation we conducted a prospective self-controlled trial with the I-Gel^™ in different degrees of neck flexion in anesthetized paralyzed children.

METHODOLOGY

The I-gel^™ was inserted in 60 children undergoing inhalation induction with muscle paralysis for routine general anesthesia. Recordings of peak inspiratory pressures (PIP) at flexion of 15°, 30°, and 45° were taken as the primary outcome. Expired tidal volume, ventilation scoring, fiberoptic gradings, and OPLP in different degrees of flexion were recorded as secondary outcomes.

RESULTS

There was a significant increase in mean PIP in cm H₂ O at flexion 30° [13.3 (95% CI 12.8-13.8) cm H₂ O, P < 0.001] and 45° flexion (16.5 [15.9-17.1] cm H₂ O, P < 0.001) compared to neutral. A decrease in the expired tidal volume was seen at flexion of 30° (7.6 [7.3-7.8] cm H₂ O, P = 0.00) and 45° (7.6 [7.3-7.8] cm H₂ O, P = 0.00). There was deterioration of ventilation score, mean [range] at 30° flexion 2[0-3], and 45° flexion 1[0-3] compared to the neutral 3[2-3]. There was a significant increase in OPLP with an increase in degree of flexion.

CONCLUSION

We conclude that 15° neck flexion can safely be applied without compromising ventilation with the I-Gel^™ in anesthetized paralyzed children. However, Flexion of 30° or more warrants caution or the use of alternative devices like an endotracheal tube due to increase in PIP and worsening of ventilation score.

A randomized prospective controlled trial comparing the laryngeal tube suction disposable and the supreme laryngeal mask airway: the influence of head and neck position on oropharyngeal seal pressure

BACKGROUND

The Laryngeal Tube Suction Disposable (LTS-D) and the Supreme Laryngeal Mask Airway (SLMA) are second generation supraglottic airway devices (SADs) with an added channel to allow gastric drainage. We studied the efficacy of these devices when using pressure controlled mechanical ventilation during general anesthesia for short and medium duration surgical procedures and compared the oropharyngeal seal pressure in different head and-neck positions.

METHODS

Eighty patients in each group had either LTS-D or SLMA for airway management. The patients were recruited in two different institutions. Primary outcome variables were the oropharyngeal seal pressures in neutral, flexion, extension, right and left head-neck position. Secondary outcome variables were time to achieve an effective airway, ease of insertion, number of attempts, maneuvers necessary during insertion, ventilatory parameters, success of gastric tube insertion and incidence of complications.

RESULTS

The oropharyngeal seal pressure achieved with the LTS-D was higher than the SLMA in, (extension (p=0.0150) and right position (p=0.0268 at 60 cm H2O intracuff pressures and nearly significant in neutral position (p = 0.0571). The oropharyngeal seal pressure was significantly higher with the LTS-D during neck extension as compared to SLMA (p= 0.015). Similar oropharyngeal seal pressures were detected in all other positions with each device. The secondary outcomes were comparable between both groups. Patients ventilated with LTS-D had higher incidence of sore throat (p = 0.527). No major complications occurred.

CONCLUSIONS

Better oropharyngeal seal pressure was achieved with the LTS-D in head-neck right and extension positions , although it did not appear to have significance in alteration of management using pressure control mechanical ventilation in neutral position. The fiberoptic view was better with the SLMA. The post-operative sore throat incidence was higher in the LTS-D.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT02856672 , Unique Protocol ID:BnaiZionMC-16-LG-001, Registered: August 2016.

Evaluation of I-gel™ airway in different head and neck positions in anesthetized paralyzed children

BACKGROUND

Studies that have compared and quantified the oropharyngeal leak pressure (OPLP) and adequacy of ventilation with supraglottic airway devices in different head and neck positions have been done in adult populations. The effects of head-neck position changes on the functioning of I-gel(™) in pediatric population still remain unevaluated.

AIM

This study aimed to quantify the influence of different head and neck positions namely neutral, maximum flexion, and maximum extension on OPLP, ventilation scoring, and fiberoptic grading using I-gel(™) in anesthetized, paralyzed children.

METHODS

I-gel(™) was inserted in 30 paralyzed, anesthetized children scheduled for elective urological and orthopedic procedures. Anesthesia was induced with sevoflurane in oxygen. Atracurium was administered intravenously to facilitate neuromuscular relaxation. Recordings of OPLP in neutral, maximum flexion, and maximum extension were taken as primary outcome. Fiberoptic grading, insertion of ryle's tube and ventilation scoring were also measured in different head and neck positions as secondary outcomes.

RESULTS

The OPLP was significantly higher in flexion (27.6 ± 3.3 cm H2 O, P = 0.000) and lower in extension (19.6 ± 3.2 cm H2 O, P = 0.006) in comparison to the neutral position (23.2 ± 3.2 cm H2 O). There was a worsening of the fiberoptic view in flexion compared to neutral position (0/5/19/6 vs 5/21/4/0). The ventilation score was poorer (1 [0-3], P < 0.05) and peak inspiratory pressures higher in flexion (15.2 ± 1.4 cm H2 O, P = 0.000) compared to the neutral position (10.4 ± 1.6 cm H2 O).

CONCLUSION

Caution is warranted in pediatric patients while ventilating with I-gel(™) in extreme flexion of head and neck owing to poor ventilation despite increase in OPLP.

Influence of Head and Neck Position on Oropharyngeal Leak Pressure and Cuff Position with the ProSeal Laryngeal Mask Airway and the I-Gel: A Randomized Clinical Trial

Background. This study was designed to assess and compare the effect of head and neck position on the oropharyngeal leak pressures and cuff position (employing fibreoptic view of the glottis) and ventilation scores between ProSeal LMA and the I-gel. Material and Methods. After induction of anesthesia, the supraglottic device was inserted and ventilation confirmed. The position of the head was randomly changed from neutral to flexion, extension, and lateral rotation (left). The oropharyngeal leak pressures, fibreoptic view of glottis, ventilation scores, and delivered tidal volumes and end tidal CO₂ were noted in all positions. Results. In both groups compared with neutral position, oropharyngeal leak pressures were significantly higher with flexion and lower with extension but similar with rotation of head and neck. However the oropharyngeal leak pressure was significantly higher for ProSeal LMA compared with the I-gel in all positions. Peak airway pressures were significantly higher with flexion in both groups (however this did not affect ventilation), lower with extension in ProSeal group, and comparable in I-gel group but did not change significantly with rotation of head and neck in both groups. Conclusion. Effective ventilation can be done with both ProSeal LMA and I-gel with head in all the above positions. ProSeal LMA has a better margin of safety than I-gel due to better sealing pressures except in flexion where the increase in airway pressure is more with the former. Extreme precaution should be taken in flexion position in ProSeal LMA.

The effect of head rotation on efficiency of ventilation and cuff pressure using the PLMA in pediatric patients

Background

This study examined whether changing the head position from neutral to side can affect expiratory tidal volume (TV) and cuff pressure when the appropriate sizes of a Proseal™ Laryngeal Mask Airway (PLMA)-depending on the body weight -are used in pediatric patients during pressure controlled ventilation (PCV).

Methods

Seventy-seven children (5-30 kg) were divided into three groups according to their body weight, PLMA#1.5 (group I, n = 24), #2 (group II, n = 26), and #2.5 (group III, n = 27). After anesthesia induction, a PLMA was placed with a cuff-pressure of 60 cmH₂O. The TV and existence of leakage at the peak inspiratory pressure (PIP) of 20 cmH₂O, and the appropriate PIP for TV 10 ml/kg were examined. Upon head rotation to the left side, the TV, PIP, cuff pressure changes, and the appropriate PIP to achieve a TV 10 ml/kg were evaluated.

Results

Head rotation of 45 degrees to the left side during PCV caused a significant increase in cuff pressure and a decrease in TV, and there was no definite leakage. Changes in PIP and TV were similar in the three groups. The cuff pressure increased but there was no significant difference between the three groups.

Conclusions

Although cuff pressure and TV of the PLMA were changed significantly after turning the head from the neutral position to the side, a re-adjustment of the cuff pressure and PIP to maintain a TV of 10 ml/kg can make the placed PLMA useful and successful in pediatric patients under general anesthesia.

The laryngeal mask airway in infants and children

PURPOSE

To compare the effectiveness of various laryngeal mask airway (LMA) sizes and their performance during positive pressure ventilation (PPV) in paralyzed pediatric patients.

METHODS

Pediatric patients (n = 158), < 30 kg, ASA 1 or 2 were studied. After paralysis, an LMA of the recommended size was inserted and connected to a volume ventilator. Fibreoptic bronchoscopy (FOB) was performed and graded: 1, larynx only seen; 2, larynx and epiglottis posterior surface seen; 3, larynx, and epiglottis tip or anterior surface seen--visual obstruction of epiglottis to larynx: < 50%; 4, epiglottis down-folded, and its anterior surface seen--visual obstruction of epiglottis to larynx: > 50%; 5, epiglottis down-folded and larynx not seen directly. Inspiratory and expiratory tidal volumes (V(T)), and airway pressure were measured by a pneumo-tachometer, and the fraction of leakage (F(L)) was calculated. In 79 cases, LMA was used for airway maintenance throughout surgery.

RESULTS

Successful LMA placement was achieved in 98% of cases: three failures were due to gastric insufflation. For LMA # 1, 1.5, 2, and 2.5, FOB grades [median (range)] were 3(1-5), 3(1-5), 1(1-5) and 1(1-3) respectively. In smaller LMAs, the cuff more frequently enclosed the epiglottis (P < .001). F(L) of LMA # 1 was higher than those of LMA # 1.5 and LMA # 2.5 (P < .05), and F(L) of LMA # 2 was higher than that of LMA # 2.5 (P < .05). In the 79 patients, the number of patients experiencing complications decreased as LMA size increased (P < .05).

CONCLUSION

Use of the LMA in smaller children results in more airway obstruction, higher ventilatory pressures, larger inspiratory leak, and more complications than in older children.

A comparison of the reinforced and standard laryngeal mask airway: ease of insertion and the influence of head and neck position on oropharyngeal leak pressure and intracuff pressure

We conducted a randomized, crossover study of 60 paralysed anaesthetized adult patients to compare ease of insertion for the reinforced (RLMA) and standard laryngeal mask airway (LMA). We also test the hypothesis that oropharyngeal leak pressure (OLP) and intracuff pressure (ICP) vary with head and neck position for the two devices. OLP and ICP were documented in four head and neck positions (neutral first, then flexion, extension and rotation in random order) for each device. The size 5 was used for all patients and the ICP was set at 60 cm H2O in the neutral position. The first time insertion success rates were similar (LMA: 60/60 v RLMA; 59/60), but insertion time was slightly less for the LMA (6 v 8 s, P = 0.004). Compared with the neutral position, OLP for the LMA was higher in flexion (21 v 28 cm H2O, P < 0.0001) and rotation (21 v 23 cm H2O, P < 0.0001), but lower in extension (21 v 14 cm H2O, P < 0.0001). Compared with the neutral position, OLP for the RLMA was higher in flexion (19 v 27 cm H2O, P < 0.0001), similar in rotation (20 v 19 cm H2O), but lower in extension (27 v 14 cm H2O, P < 0.0001). The difference in OLP between flexion and extension was 13 and 14 cm H2O for the RLMA and LMA respectively. OLP was slightly higher for the LMA compared with the RLMA when the head was in neutral (P < 0.0001) and rotation (P < 0.0001), but was similar during flexion and extension. There was a significant positive correlation between ICP and OLP for the LMA (P < 0.0001) and RLMA (P < 0.0001). We conclude that ease of insertion is similar for the RLMA and LMA. OLP is higher with head/neck flexion and lower with extension for both devices and is associated with a similar change in ICP. We recommend assessing the efficacy of seal for all head and neck positions likely to be encountered prior to the start of surgery.

The influence of head and neck position on oropharyngeal leak pressure and cuff position with the flexible and the standard laryngeal mask airway

We conducted a randomized, cross-over study of 20 paralyzed anesthetized adult patients to test the hypothesis that oropharyngeal leak pressure and cuff position (assessed fiberoptically) vary with head and neck position for the flexible (FLMA) and standard laryngeal mask airway (LMA). Both devices were inserted into each patient in random order. Oropharyngeal leak pressure and fiberoptic position (including degree of rotation) were documented in four head and neck positions (neutral first, then flexion, then extension and rotation in random order) for each device. The size 5 was used for all patients, and the intracuff pressure was set at 60 cm H2O in the neutral position. All airway devices were inserted at the first attempt. Oropharyngeal leak pressure was similar for the FLMA and LMA in the neutral (22 vs 21 cm H2O), flexed (26 vs 26 cm H2O), and extended positions (19 vs 18 cm H2O) but was slightly higher for the LMA when the head was rotated (19 vs 22 cm H2O; P = 0.04). Compared with the neutral position, oropharyngeal leak pressure for the LMA was higher with flexion (26 vs 21 cm H2O; P = 0.0004) and lower with extension (18 vs 21 cm H2O; P = 0.03) but similar with rotation. Compared with the neutral position, oropharyngeal leak pressure for the FLMA was higher with flexion (26 vs 22 cm H2O; P = 0.0001) and lower with extension (19 vs 22 cm H2O; P = 0.03) and rotation (19 vs 22 cm H2O; P = 0.03). The difference in oropharyngeal leak pressure between flexion and extension was 7 and 8 cm H2O for the FLMA and LMA, respectively. Fiberoptic position was similar between devices and was unchanged by head and neck position. Rotation was not detected fiberoptically. We conclude that there are small changes in oropharyngeal leak pressure but no changes in cuff position in different head and neck positions for the FLMA and LMA. Oropharyngeal leak pressure may be improved by head and neck flexion and by avoiding extension.

IMPLICATIONS

There are small changes in oropharyngeal leak pressure but no changes in cuff position in different head and neck positions for the flexible and standard laryngeal mask airways. Oropharyngeal leak pressure may be improved by head and neck flexion and by avoiding extension.

An evaluation of the factors influencing selection of the optimal size of laryngeal mask airway in normal adults

The purpose of this randomised single blinded study was to determine the optimal size of laryngeal mask airway in the normal adult population, to test the validity of the current selection criteria and to determine if any externally measured anatomical variable correlated with optimal size. In each of 30 apnoeic anaesthetised adults weighting less than 100 kg, size 3, 4 and 5 laryngeal mask airways were inserted in random order by a skilled user and the cuff inflated to a standard pressure (60 cm H2O). Optimal size was based on four criteria in order of priority: number of attempts at placement, oropharyngeal leak pressure, fiberoptic score and percentage of vocal cords seen. The size 5 laryngeal mask airway was optimal in 19/30 and the size 4 in 11/30. In no patient was the size 3 the optimal fit. Oropharyngeal leak pressure was significantly higher for each progressively large size and the fiberoptic view was significantly better for the size 4 and size 5. There was no significant predictive value in any externally measured anatomical variable, but height was the most useful. The best current selection strategy was to choose a size 5 for males and size 4 for females. Potentially useful new strategies may be to use the size 5 in all adults, or a size 5 > or = 165 cm in height and size 4 for < 165 cm. We conclude that predicting the optimal size of laryngeal mask airway for individual adult patients is complex. The best size selection strategies involve use of the size 4 and 5 laryngeal mask airways in adults.