Cuff filling volumes and pressures in pediatric laryngeal mask airways

Efficacy and safety of three inflation methods of the laryngeal mask airway Ambu® Auraonce™: a randomized controlled study

The laryngeal mask airway (LMA) is commonly used for airway management. Cuff hyperinflation has been associated with complications, poor ventilation and increased risk of gastric insufflation. This study was designed to determine the best cuff inflation method of AuraOnce™ LMA during bronchoscopy and EBUS (Endobronquial Ultrasound Bronchoscopy) procedure. We designed a Randomized controlled, doble-blind, clinical trial to compare the efficacy and safety of three cuff inflation methods of AuraOnce™ LMA. 210 consenting patients scheduled for EBUS procedure under general anesthesia, using AuraOnce™ LMA were randomized into three groups depending on cuff insufflation: residual volume (RV), half of the maximum volume (MV), unchanged volume (NV). Parameters regarding intracuff pressure (IP), airway leak pressure (OLP), leakage volume (LV) were assessed, as well as postoperative complications (PC). 201 (95.7%) patients completed the study. Mean IP differed between groups (MV: 59.4 ± 32.4 cm H2O; RV: 75.1 ± 21.1 cm H2O; NV: 83.1 ± 25.5 cmH20; P < 0.01). The incidence of IP > 60 cmH2O was lower in the MV group compared to the other two (MV: 20/65(30.8%); RV:47/69 (68.1%); NV 48/67 (71.6%); p < 0.01). The insertion success rate was 89,6% (180/201) at first attempt, with no difference between groups (p = 0.38). No difference between groups was found either for OLP (p = 0.53), LV (p = 0.26) and PC (p = 0.16). When a cuff manometer is not available, a partial inflation of AuraOnce™ LMA cuff using MV method allows to control intracuff pressure, with no significant changes of OLP and LV compared to RV and NV insufflation method.Registration clinical trial: NCT04769791.

Comparison of weight-based and pinna size method for ProSeal laryngeal mask airway size selection in children receiving general anesthesia: A randomized clinical study

Background and Aims

Several methods are in use for LMA ProSeal™ size selection in pediatric patients. Weight-based method is most commonly used. Pinna size-based method is a promising new technique for accurate size selection.

Material and Methods

A total of 146 children aged between 6 months and 12 years undergoing surgery under general surgery were included. They were randomized into either pinna-based group (group X) or weight-based group (group Y). Both groups were compared for accurate placement of ProSeal™ laryngeal mask airway (PLMA), ease of insertion, number of attempts needed, and peak airway pressures.

Results

A Comparable number of patients had a Brimacombe score of 3 and above, indicating correct placement in both groups (P = 0.407). PLMA was easily inserted in 79.5% and 87.7% of patients of groups X and Y, respectively (P = 0.180). Insertion was found to be difficult in 20.5% of patients in group X, whereas it was difficult in only 12.3% of patients of group Y (P = 0.180). The two groups were comparable as per the number of attempts needed for insertion (P = 0.161). Mean peak airway pressures too were comparable between both groups. Ease of insertion too, was statistically insignificant between both groups.

Conclusions

Pinna size-based estimation of LMA size is an effective alternative method to weight-based selection.

Effect of diffusion of anaesthetic gases on fibre-optic view change of laryngeal mask airway and post-operative laryngo-pharyngeal morbidity in children - A randomised controlled trial

Background and Aims:

The diffusion of nitrous oxide (N₂O) into the air-filled cuff of the classic laryngeal mask airway (LMA) may lead to an increase in cuff pressure (CP) and displacement of LMA affecting its performance. This study was conducted to evaluate the change in optimal position of LMA by fibre-optic bronchoscope, the changes in cuff pressure and oropharyngeal leak pressure (OLP), and post-operative laryngo-pharyngeal morbidity during N₂O–oxygen (O₂) anaesthesia in children.

Methods:

After ethics committee approval and written informed consent, 84 children, aged 2 to 8 years undergoing lower abdominal surgery using LMA were included. Anaesthesia was induced with sevoflurane and maintained with either 33% O₂ in air (Group 1) or with 33% O₂ in 67% N₂O (Group 2) along with sevoflurane. The position of LMA using fibre-optic bronchoscope, CP and OLP were recorded at 30, 60 and 90 minutes and at the end of surgery. The incidence of post-operative sore throat, hoarseness of voice and dysphagia was assessed for 24 hours.

Results:

A mild (Grade 1) change in fibre-optic position of LMA was observed in 6 out of 42 children maintained with N₂O–O₂ anaesthesia. The cuff pressure was higher than baseline in group 2 at all three time points with the maximum at 90 minutes (93.23 ± 14.86 cm H₂O vs. 39.78 ± 7.75 cm H₂O; P < 0.05). The OLP was comparable between the groups during the initial 60 minutes and then increased in group 2. The incidence of post-operative sore throat was significantly higher in group 2 (P = 0.008).

Conclusion:

The diffusion of anaesthetic gases into the air-filled cuff does not change the fibre-optic position of the LMA significantly but increases the cuff pressure and incidence of post-operative laryngo-pharyngeal complications in children.

Correlation and variation of cuff inflating volumes and pressures in different adult models of laryngeal mask: a prospective randomized trial

BACKGROUND

Hyperinflation of laryngeal mask cuffs may carry the risk of airway complications. The manufacturer recommends inflating cuff until the intracuff pressure reaches 60 cmH2O, or inflate with the volume of air to not exceed the maximum recommended volume. We prospectively assessed the correlation of cuff inflating volumes and pressures, and the appropriated the cuff inflating volumes to generate an intracuff pressure of 60 cmH2O in the adult laryngeal masks from different manufacturers.

METHODS

Two groups of 80 patients requiring laryngeal mask size 3 and 4 during general anesthesia were randomized into 4 subgroups for each size of the laryngeal mask: Soft Seal® (Portex®), AuraOnce™ (Ambu®), LMA-Classic™ (Teleflex®) and LMA-ProSeal™ (Teleflex®). After insertion, the cuff was inflated with 5-ml increments of air up to the maximum recommended volume. After each 5-ml intracuff pressure was measured, the volume of air that generated the intracuff pressure of 60 cmH2O was recorded.

RESULTS

Mean (SD) volume of air required to achieve the intracuff pressure of 60 cmH2O in Soft Seal®, AuraOnce™, LMA-Classic™, LMA-ProSeal™ laryngeal mask size 3 were 11.80(1.88), 9.20(1.88), 8.95(1.50) and 13.50(2.48) ml, respectively, and these volumes in laryngeal mask size 4 were 14.45(4.12), 12.55(1.85), 11.30(1.95) and 18.20(3.47) ml, respectively. The maximum recommended volume resulted in high intracuff pressures (> 60 cmH2O) in all laryngeal mask types and sizes studied.

CONCLUSION

Pressure-volume curves of adult laryngeal masks are all in sigmoidal shape. Cuff designs and materials can effect pressure and volume correlation. Approximately half of the maximum recommended volume is required to achieve the intracuff pressure of 60 cmH2O except LMA-ProSeal™ which required two-thirds of the maximum recommended volume.

TRIAL REGISTRATION

Thai Clinical Trials Registry, TCTR20150602001, May 28, 2015.

Comparison of weight-based and pinna size-based selection of ProSeal laryngeal mask airway in paediatric population - A prospective exploratory trial

Background and Aims

Weight-based selection of ProSeal laryngeal mask airway (PLMA) size may be unreliable in some situations. The aim of this study was to compare the ventilation parameters using PLMA during controlled ventilation between weight-based size selection and pinna size-based selection in children.

Methods

A total of 204 patients were randomised to receive either pinna size-based (Group P) or weight-based (Group W) size selection of PLMA. We tested the hypothesis that pinna size-based selection of PLMA was better than weight-based selection of PLMA in paediatric patients during controlled ventilation under general anaesthesia in terms of oropharyngeal sealing pressure (the primary end-point) and Brimacombe score. Cuff pressure was maintained at 60 cm of H₂O during the study. Secondary outcomes included the number of attempts for successful placement of PLMA, peak airway pressure, gastric tube placement, traumatic insertion, and complications were also compared. Parametric variables were analysed using unpaired t-test and categorical variables were analysed using Mann-Whitney and Chi-square test.

Results

In all, 200 patients were analysed. The mean oropharyngeal sealing pressure in Group P was 25.4 ± 3.5 cmH₂O and 24.9 ± 3.8 cmH₂O in Group W, (P = 0.34). There was no significant difference between the two groups in any of the secondary outcomes. There were no traumatic insertion or complications reported in both the groups.

Conclusion

Pinna-based size selection method can be used in PLMA placement in the paediatric population for positive pressure ventilation and it serves as an alternative method to weight-based selection.

Clinical application of limiting laryngeal mask airway cuff pressures utilizing inflating syringe intrinsic recoil

BACKGROUND

Overinflation of the laryngeal mask airway (LMA) cuff may cause many of the complications associated with the use of the LMA. There is no clinically acceptable (cost effective and practical) method to ensure cuff pressure is maintained below the manufacturer's recommended maximum value of 60 cm H2O (44 mmHg). We studied the use of the intrinsic recoil of the LMA inflating syringe as an effective and practical way to limit cuff pressures at or below the manufacturer's recommended values.

METHODS

We enrolled 332 patients into three separate groups: LMAs inserted and inflated per standard practice at the institution with only manual palpation of the pilot balloon; LMA cuff pressures measured by a pressure transducer and reduced to < 60 cm H2O (44 mmHg); and LMA intra-cuff pressure managed by the intrinsic recoil of the syringe.

RESULTS

There were no statistically significant differences between the pressure transducer group and the syringe recoil group for initial cuff pressure or cuff pressure 1 hour after surgery. Both the syringe recoil group and pressure transducer group were less likely than the standard practice group to have sore throat and dysphagia 1 hour after surgery. These differences remained 24 hours after surgery.

CONCLUSIONS

Syringe recoil provides an efficient and reproducible method similar to manometry in preventing overinflation of the LMA cuff and decreasing the incidence of postoperative laryngopharyngeal complications.

Ambu AuraOnce versus i-gel laryngeal mask airway in infants and children undergoing surgical procedures. A randomized controlled trial

Objectives:

To compare the efficacy and performance of the pediatric Ambu AuraOnce (Ambu AO) mask (Ambu, Copenhagen, Denmark) and i-gel mask (Intersurgical Ltd., Wokingham, United Kingdom).

Methods:

From May 2015 to September 2016, 112 patients, 0-14 years old, underwent elective surgery at a tertiary university hospital (Riyadh, Saudi Arabia). They were randomly assigned to the Ambu AO or i-gel group. Three groups underwent a subgroup analysis: ≤5 kg (group 1), 5.1–10.0 kg (group 2), and >10 kg (group 3).

Results:

The oropharyngeal leak pressure was significantly higher for the i-gel (25.4±4.1 cm H₂O) than for the Ambu AO (22.5±3.9 cm H₂O, p<0.001). The Ambu AO had a slightly higher ease of insertion compared to the i-gel (100% versus 94%, p=0.08) and required less manipulation (2% versus 11%, p=0.07).The Ambu AO and i-gel showed non-significant differences in performance between weight groups. There were statistically significant differences for higher leak pressure in group 2 (p=0.01) and group 3 (p=0.002) in favor of the i-gel, and for less manipulation in the Ambu AO in group 1 (p=0.04). Fiberoptic viewing was superior in group 2 for the i-gel (p=0.03) and in group 3 for the Ambu AO (p=0.02).

Conclusion:

Both devices demonstrated equally good performance with low morbidity. The Ambu AO had a statistical tendency towards easier insertion and less manipulation. Confirming this finding will require large scale trials.

Cuffed tracheal tubes in children: past, present and future

This article reviews recent developments and core topics in the use and design of pediatric cuffed tracheal tubes. A concept for an appropriate pediatric cuffed tracheal tube is introduced. The main points in this concept are evidence-based tracheal tube size recommendation, continuous cuff pressure monitoring and a pediatric tracheal tube with an anatomically-based intubation depth mark and a short distally placed high-volume-low pressure cuff made from an ultra-thin polyurethane membrane with markedly improved tracheal sealing performance. The main points in proper handling of cuffed tracheal tubes in children are highlighted. Finally, an outlook on future developments in the design of pediatric cuffed tracheal tubes and an overview of tasks to be performed in evaluating them is given.

Comparison of Size 2 LMA-ProSeal™ and LMA-Supreme™ in Spontaneously Breathing Children: a Randomised Clinical Trial

OBJECTIVE

The aim of this study was to compare size 2 Laryngeal Mask Airway ProSeal and size 2 Laryngeal Mask Airway Supreme in spontaneously breathing children undergoing lower abdominal elective surgery of <1 hour duration.

STUDY DESIGN

Randomized clinical trial.

MATERIAL AND METHODS

Sixty children aged 1-7 years, weighing 10-20 kg, ASA I physical status were randomly allocated to the Laryngeal Mask Airway ProSeal and Laryngeal Mask Airway Supreme.

RESULTS

There were no differences in demographic variables, ease of gastric tube placement, ease of insertion and ventilation, number of insertion attempts, hemodynamic changes on insertion, postoperative complications and bloodstaining between the groups. Gastric insufflation was detected and gastric tube was placed in all patients except one in LMA Supreme. Postoperative cuff volumes were comparable with the preoperative values in group itself. Oropharyngeal leak pressures were higher in Laryngeal Mask Airway ProSeal (24.6±5.5 vs 21.3±4.2, respectively; p<0.01).

CONCLUSION

As a result Laryngeal Mask Airway ProSeal and Laryngeal Mask Airway Supreme can safely be used in spontaneously breathing pediatric population undergoing lower abdominal elective surgery.

Cuff filling volumes for pediatric classic laryngeal mask airways: comparison of clinical end points versus adjusted cuff pressure

BACKGROUND

Clinical end points are often used to guide inflation and adequacy of cuff seal after laryngeal mask airway placement. However, clinical end points for cuff inflation have been shown to have significantly higher intracuff pressure. The adjusted cuff pressure between 55 and 60 cm H(2)O causes significantly better seal of laryngeal mask airway. We prospectively assessed the cuff pressures generated by cuff inflation guided by clinical end points, and the actual volume of air required to achieve cuff pressures between 55 and 60 cm H(2)O for sizes 1-2.5 reusable classic laryngeal mask airway.

METHODS

Two hundred and three ASA I and II children undergoing elective cataract surgery requiring general anesthesia receiving laryngeal mask airway sizes 1-2.5 were recruited to this study. The laryngeal mask airway was placed using standard technique. After insertion of laryngeal mask airway, the cuff was slowly inflated until a slight outward shift of device was noted. Cuff pressures were measured using calibrated hand held Portex Cuff Inflator Pressure Gauge (Portex Limited, Hythe, Kent, UK). If the cuff pressure was >60 cm H(2)O, the cuff was deflated to achieve a cuff pressure of 55-60 cm H(2)O. The volume of air required to achieve this pressure was recorded.

RESULTS

The volume of air required to achieve the pressure between 55 and 60 cm H(2)O in laryngeal mask airway size 1, 1.5, 2.0, and 2.5 were 2.750 ± 0.2565, 4.951 ± 0.5378, 6.927 ± 0.6328, and 10.208 ± 1.4535 ml, respectively. The difference between the initial and the final cuff volumes and pressures in all laryngeal mask airway sizes were statistically significant(P = 0.000).

CONCLUSION

Lower cuff volumes are required to achieve a pressure of 60 cm H(2)O than those required if clinical end points are used as a sole guide for determining cuff inflation for patients receiving pediatric laryngeal mask airways.

A novel method for laryngeal mask airway size selection in paediatric patients

CONTEXT

The successful use of the laryngeal mask airway in children partly depends on the correct selection of size. Most anaesthesiologists rely on the weight-based table which is often difficult to remember. A simple method allowing an adequate choice of the correct size may be highly desirable.

OBJECTIVES

To test the hypothesis that the size of the external ear (pinna) of the child may be used as proxy for the required size of laryngeal mask airway.

DESIGN

A descriptive study.

SETTING

King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia.

PATIENTS

Two hundred and ten paediatric patients aged 6 months to 15 years, of either sex, American Society of Anesthesiologists (ASA) 1-2 and scheduled for routine ophthalmological procedures from 1 March to 31 December 2010. Emergency cases, patients with a full stomach or with a history of any oropharyngeal lesion other than tonsillar hypertrophy were excluded.

MAIN OUTCOME MEASURES

The size of the external ear was measured with a ruler in vertical and horizontal dimensions in the first 30 patients, and visually evaluated for the remaining patients. For all, the nearest corresponding size of partially inflated laryngeal mask airway was chosen and inserted after induction. The correct placement was assessed using predefined criteria.

RESULTS

Insertion and good ventilation was achieved in 196 (93.3%) on first attempt. Fourteen patients (6.7%) required a second attempt and the main reason for failure was an audible leak because of smaller size.

CONCLUSION

Choosing the size of the laryngeal mask airway in children according to the size of the external ear was associated with a success rate of 93% which is comparable with that reported in the literature when the tables are used. This simple method may allow a rapid choice of the correct size of laryngeal mask airway and may eliminate the need to remember different tables or formulae.

Pediatric airway management: current practices and future directions

Management of a pediatric airway can be a challenge, especially for the non-pediatric anesthesiologists. Structured algorithms for an unexpected difficult pediatric airway have been missing so far. A recent step wise algorithm, based on the Difficult Airway society (DAS) adult protocol, is a step in the right direction. There have been some exciting advances in development of pediatric extra-glottic devices for maintaining ventilation, and introduction of pediatric versions of new 'non line of sight' laryngoscopes and optical stylets. The exact role of these devices in routine and emergent situations is still evolving. Recent advances in simulation technology has become a valuable tool in imparting psychomotor and procedural skills to trainees and allied healthcare workers. Moving toward the goal of eliminating serious adverse events during the management of routine and difficult pediatric airway, authors propose that institutions develop a dedicated Difficult Airway Service comprising of a team of experts in advanced airway management.

A simple method of partial inflation of the LMA cuff before insertion in children to allow cuff pressure without adjustment after insertion

Background

The cuff of the laryngeal mask airway (LMA) is preferred to be partially inflated before insertion in pediatric cases. However, it is not known how much inflation is appropriate. In addition, intra-cuff pressure is not routinely monitored in many institutions despite the fact that a neglected high cuff pressure could cause several complications. This study was conducted to determine whether the cuff inflated with its resting volume before insertion could have a clinically tolerable intra-cuff pressure after insertion.

Methods

One hundred fifty unpremedicated children aged 0 to 9 yrs were enrolled. The pilot balloon valve was connected to a piston-free syringe to keep the valve open to the atmosphere and allowing the pressure within the cuff of to LMA to equalize to atmospheric pressure. Anesthesia was induced with 6 vol% of sevoflurane in oxygen. After insertion and final positioning of the LMA, the intra-cuff pressure was measured using a cuff pressure manometer.

Results

The mean intra-cuff pressure was 50 ± 12.9 cmH₂O; intra-cuff pressures were 39.1 ± 9.3, 51.6 ± 11.2, and 64.6 ± 12.5 cmH₂O for LMAs of sizes 1.5, 2, and 2.5, respectively. Intra-cuff pressure of more than 60 cmH₂O was measured in 26 patients, and the median value was 70 cmH₂O. There was weak statistical correlation among age, height, and weight with intra-cuff pressure.

Conclusions

The cuff inflated by the resting volume before insertion may be a simple method for guaranteeing tolerable cuff pressure after insertion.

The laryngeal mask in infants and children: what is the cuff pressure?

BACKGROUND

Unintended hyperinflation of the cuff of a laryngeal mask airway (LMA) has been associated with increased airway morbidity and postoperative pain. While the manufacturers recommend a cuff pressure of less than 60 cmH(2)O, in usual clinical practice, there is no method used to determine intracuff pressure of an LMA. The purpose of this prospective quality assurance study is to evaluate the incidence of LMA hyperinflation and excessive intracuff pressure in a busy tertiary care pediatric hospital.

METHODS

There was no change dictated in clinical practice for these patients. Per our usual practice, the LMA was removed from the package and inserted with the cuff partially inflated. The cuff was further inflated as needed to ensure a seal during positive pressure ventilation to a peak inflating pressure of 20-25 cmH(2)O. During the first 30 min of the case, the pressure in the cuff of the LMA was measured using a hand held manometer. Additional data collected included the patient's demographic data (age, weight, and gender), the size of the ETT, and whether nitrous oxide was in use.

RESULTS

Of the 200 subjects in the current study, 106 had an LMA cuff pressure ≥ 60 cmH(2)O (53%). Patients who were greater than 8 years of age had significantly higher average cuff pressures and significantly more LMAs with an intracuff pressure ≥ 60 cmH(2)O when compared to patients younger than 4 years of age and patients 4-8 years of age. Similarly, larger LMAs were found to have significantly higher intracuff pressures.

CONCLUSIONS

Using current clinical practice to inflate the cuff of the LMA, a significant percentage of pediatric patients have an intracuff pressure greater than the generally recommended upper limit of 60 cmH(2)O. Risk factors identified in our study included age of the patient and the size of the 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.

Prospective evaluation of the self-pressurized air-Q intubating laryngeal airway in children

OBJECTIVES

To assess the clinical efficacy of the self-pressurized air-Q ILA™ (ILA-SP).

AIM

  The purpose of this prospective audit was to evaluate the feasibility of the ILA-SP in clinical practice and generate data for future comparison trials.

BACKGROUND

The ILA-SP is a new first-generation supraglottic airway for children with a self-adjusting cuff and lack of a pilot balloon.

METHODS

Over a 4-month period, 352 children with an ASA physical status of I-III, newborn to 18 years of age, undergoing various procedures were studied. Data points assessed included insertion success rates, airway leak pressures, quality of ventilation, and perioperative complications associated with the use of this device.

RESULTS

In 349 of the 352 patients in this study, the ILA-SP was used successfully as a primary supraglottic airway device in a variety of patients. Three patients required conversion to a standard laryngeal mask airway or a tracheal tube. The mean initial airway leak pressure for all patients was 17.8 ± 5.4 cm H(2)O, and 20.4 ± 5.5 cm H(2)O when re-checked at 10 min, which was statistically significant (P < 0.001). Complications were limited to 14 patients and related to reflex activation of the airway (coughing, laryngospasm, and bronchospasm) (n = 10), sore throat (n = 3), and blood staining on removal of the device (n = 1). There were no episodes of regurgitation, aspiration, or hoarseness.

CONCLUSIONS

Acceptable clinical performance was demonstrated with the ILA-SP for a variety of procedures in infants and children with spontaneous and positive pressure ventilation. Future studies comparing this device to other supraglottic airways may provide useful information regarding the safety of the ILA-SP in pediatric clinical practice.

Crossover comparison of airway sealing pressures of 1.5 and 2 size LMA-ProSeal™ and LMA-Classic™ in children, measured with the manometric stability test

OBJECTIVES

To compare airway sealing pressures, air leak, optimal positioning of the LMA-ProSeal™ and LMA-Classic™ in children.

METHODS

A crossover, randomized study was conducted in children aged 6 months-7 years weighing <20 kg scheduled for minor elective surgery under GA with sevoflurane. Either a 1.5 or 2-size LMA-ProSeal™ or LMA-Classic™ was inserted first. Optimal position of the devices was evaluated by fiberoptic bronchoscopy (FOB). Airway sealing pressures were determined under standardized conditions by the manometric stability test at the proximal end of the LMA device. Gas leak observed by auscultation over the neck and epigastrium was noted at these pressures.

RESULTS

Twenty-seven children of mean ages 29.48 ± 19.81 months and mean weight 11.23 ± 3.28 kg were included for evaluation. Airway sealing pressures were noted to be similar: 23.11 ± 8.28 cm H(2)O with LMA-ProSeal™ and 23.26 ± 8.21 cm H(2)O with LMA-Classic™. At these sealing pressures, air leak in the neck was observed in 21/27 children with LMA-ProSeal™ compared with 24/27 with LMA-Classic™ (P = 0.467). Optimal device positioning as viewed by FOB was seen in 14/27(51.8%) children with LMA-ProSeal™ and 15/27(55.6%) with LMA-Classic™. Airway sealing pressures with suboptimal position of LMA-ProSeal™ was 22.23 ± 10.23 cm H(2)O and with optimal position 23.93 ± 6.25 cm H(2)O (P = 0.612).

CONCLUSION

The LMA-ProSeal™ and LMA-Classic™ size 1.5 and 2 provide similar mean airway sealing pressures as assessed by the manometric stability test under standardized conditions, with similar air leak and optimal positioning.

Reduced air leakage by adjusting the cuff pressure in pediatric laryngeal mask airways during spontaneous ventilation

BACKGROUND

Optimal inflation of the laryngeal mask airway (LMA) cuff should allow ventilation with low leakage volumes and minimal airway morbidity. Manufacturer's recommendations vary, and clinical end-points have been shown to be associated with cuff hyperinflation and increased leak around the LMA. However, measurement of the intra-cuff pressure of the LMA is not routine in most pediatric institutions, and the optimal intra-cuff pressure in the LMA has not been determined in clinical studies.

METHODS

This was a prospective audit in 100 pediatric patients undergoing elective general anesthesia breathing spontaneously via LMA (size 1.5-3). Cuff pressure within the LMA was adjusted using a calibrated pressure gauge to three different values (60, 40, and 20 cmH2O) within the manufacturers' recommended LMA cuff pressure range (< or = 60 cmH2O). Three corresponding inspiratory and expiratory tidal volumes were recorded, and the differences were calculated as the 'leak volume'.

RESULTS

Compared with 20 and 60 cmH2O intra-cuff pressure, measured leakage volumes were the lowest at cuff inflation pressures of 40 cmH2O [median (range) 0.42 (0.09-1.00) ml x kg(-1)] in most patients (83%), while 17% of children demonstrated minimally smaller leakages at 20 cmH2O [0.51 (0.11-1.79) ml x kg(-1)]. Maximum leakage values occurred with cuff pressures of 60 cmH2O in all groups [0.65 (0.18-1.27) ml x kg(-1)] and were not associated with the smallest value of air leakage in any patient.

CONCLUSION

Using cuff manometry, an intra-cuff pressure of 40 cmH2O was associated with reduced leak around the LMA while higher (60 cmH2O) and lower (20 cmH2O) cuff pressures resulted in higher leak volumes during spontaneous ventilation. In spontaneously breathing children, reducing the intra-cuff pressure of pediatric-sized LMAs even below the manufacturers' recommendations allows ventilation with minimized leakage around the LMA cuff.

Recent advances in airway management in children

Recent anatomic findings, technological progress, and both in vitro and in vivo studies of the pressure generated in the cuff of endotracheal tubes and supraglottic airways should lead to modification of the way we control the pediatric upper airway.

Laryngeal mask airways--to inflate or to deflate after insertion?

BACKGROUND

Hyperinflation of the laryngeal mask airway (LMA) cuff is known to be a risk factor for airway morbidity and increased leakage around the LMA. While the manufacturers' recommendation is to inflate the cuff with the maximum recommended volumes and/or to adjust the cuff pressure to <60 cmH2O, cuff pressures below 40 cmH2O have been shown to be associated with a minimal rate of sore throat and minimal leakage. However, it remains to be determined whether inflation or deflation is needed to achieve favorable pressures. Therefore, we assessed the need for cuff-volume adjustment following insertion of the LMA unchanged straight from the sterile packaging in a prospective audit.

METHODS

One thousand children (0-16 years) undergoing elective surgery were consecutively included in this quality of care audit. After taking the LMA from its sterile packaging, the LMA cuff was emptied and the amount of air recorded. Then, the same amount of air was returned into the LMA, the LMA was inserted into the patient, and the cuff pressure was measured using a calibrated cuff manometer.

RESULTS

Following insertion of the LMA (without further inflation or deflation of the cuff), 20.5% of children had cuff pressures > or = 60 cmH2, while 55.7% had LMA cuff pressures <40 cmH2O. Cuff pressures were also significantly higher in size 1 LMAs (66.6% had cuff pressures > or = 60 cmH2O and 2% <40 cmH2O) compared with all other sizes (P < 0.05). Furthermore, cuff pressures in LMAs with a poly vinyl chloride (PVC) surface were higher compared to LMAs with a silicone surface (65.2% > or = 60 cmH2O and 9.3% <40 cmH2O vs 9% > or = 60 cmH2O and 67.6% <40 cmH2O, respectively).

CONCLUSIONS

This study demonstrates that LMAs, particularly when using small-sized LMAs or LMAs with a more rigid PVC surface, need to be deflated following insertion of the device rather than inflated to avoid cuff hyperinflation. Hence, cuff pressures should be measured routinely using a manometer to minimize potential pressure-related airway complications.

Comparison of different techniques of laryngeal mask placement in children

PURPOSE OF REVIEW

The insertion of laryngeal mask airway is not always easy in children, and many techniques are described to improve success rate of placement. It is very important to determine the optimal insertion technique as unsuccessful prolonged insertion and multiple attempts are associated with adverse respiratory events and trauma in children. This article will review different techniques studied recently for the placement of classical laryngeal mask airway in children as well as recent findings of cuff pressure and depth of anesthesia for laryngeal mask airway placement. Laryngeal mask airway in children has undergone many modifications such as ProSeal laryngeal mask airway to improve its functioning. This article will also review different insertion techniques for ProSeal laryngeal mask airway.

RECENT FINDINGS

Rotational technique with partially inflated cuff is reported to have the highest success rate of insertion and lowest incidence of complications for classical laryngeal mask airway in children. Clinical endpoints for cuff inflation are associated with significant hyperinflation and increased leakage around the laryngeal mask airway cuff. The inferences regarding the dosage of intravenous anesthetic agents and end-tidal concentration of volatile anesthetics in children to achieve adequate depth for laryngeal mask airway placement are very difficult to draw. ProSeal laryngeal mask airway is associated with a very high first attempt success and overall success of insertion in children.

SUMMARY

Rotational technique may be considered as the first technique of choice for classical laryngeal mask airway insertion in children. The routine use of cuff pressure monitoring is mandatory during the use of laryngeal mask airway in children. Modification of laryngeal mask airway in children, that is ProSeal laryngeal mask airway, is promising and improves the success rate of insertion.

Impact of laryngeal mask airway cuff pressures on the incidence of sore throat in children

BACKGROUND

Hyperinflation of laryngeal mask airway cuffs can cause harm to the upper airway mainly by exerting high pressures on pharyngeal and laryngeal structures thus impairing mucosal perfusion. Although cuff manometers can be used to guide the monitoring of cuff pressures, their use is not routine in many institutions. In a prospective audit, we assessed the incidence of sore throat following day-case-surgery in relation to the intracuff pressure within the laryngeal mask airway.

METHODS

Four hundred children (3-21 years) were consecutively included in this study. The laryngeal mask airway was inflated as deemed necessary by the attending anesthetist. Cuff pressures were measured using a calibrated cuff manometer (Portex Limited, Hythe, Kent, UK, 0-120 cm H2O, pressures exceeding the measurement range were set at 140 cm H2O for statistical purposes) at induction of anesthesia.

RESULTS

Forty-five children (11.25%) developed sore throat, 32 (8%) sore neck and 17 (4.25%) sore jaw. Of those that developed sore throat, 56.5% had cuff pressures exceeding >100 cm H2O. In contrast, when cuff pressures were <40 cm H2O, there were no episodes of sore throat, whilst there was only a 4.6% occurrence of sore throat if cuff pressures were between 40-60 cm H2O.

CONCLUSION

We have demonstrated that intra cuff pressure in laryngeal mask airways is closely related to the development of sore throat with higher pressures increasing its likelihood. Hence, cuff pressures should be measured routinely using a manometer to minimize the incidence of sore throat.

Lower cuff pressures improve the seal of pediatric laryngeal mask airways

BACKGROUND

Hyperinflation of laryngeal mask airway (LMA) cuffs may be harmful because of the exertion of high pressures on pharyngeal and laryngeal structures. Although cuff manometers may be used to monitor cuff pressure, their use is not routine in many institutions and clinical endpoints are used instead. Furthermore, it is common clinical practice to add air to the cuff in the presence of an air leak to obtain a better seal.

METHODS

In a prospective audit, the authors assessed air leakage around pediatric sized LMAs (n = 200) following inflation guided by common clinical endpoints (slight outward movement of the LMA) and then following adjustment of the cuff pressure to the recommended pressure range (<60 cmH(2)O) according to institutional guidelines with the use of a calibrated cuff manometer, directly after induction of anesthesia. Following induction, all children were gently ventilated with pressure control ventilation with 10 cmH(2)O and a positive end-expiratory pressure of 5 cmH(2)O.

RESULTS

Following inflation of the cuff guided by clinical endpoints, the median initial cuff pressure (LMA size 1-3) was 92 (size 3) to >120 cmH(2)O (size 1) and the median leakage around the cuff ranged from 0.66 to 1.07 ml x kg(-1). Following cuff pressure adjustment according to the recommended pressure range (<60 cmH(2)O), the leakage decreased significantly to 0.51-0.79 ml x kg(-1) (P = 0.002 for size 1, P < 0.001 for size 1.5-3).

CONCLUSION

The use of clinical endpoints to inflate LMA cuffs is not only associated with significant hyperinflation in the majority of patients but also with an increased leakage around the LMA cuff when compared with adjusted LMA cuff pressures. Therefore, cuff manometers should routinely be used not only to avoid unnecessary hyperinflation but also to improve cuff sealing of LMA in children.

Larynxmaske

Introduction of the laryngeal mask airway (LMA) has been a revolutionary development in airway management over the last decades. It was first used clinically in 1981 by A. Brain and has been widely used in Germany since 1990. Originally intended as a substitute for conventional mask respiration for short periods of general anaesthesia, the laryngeal mask is in the meantime used in many areas as an alternative to elective endotracheal intubation as well as an option for controlling difficult airways. This contribution provides an overview of the basics as well as practical aspects of LMA use, and discusses the possibilities and limitations of the laryngeal mask in daily practice.

A randomized prospective study comparing the Cobra Perilaryngeal Airway and Laryngeal Mask Airway-Classic during controlled ventilation for gynecological laparoscopy

BACKGROUND

An increasing number of noninvasive, supraglottic airway devices are currently available. In this randomized single-blind study, we compared the Cobra Perilaryngeal Airway (CobraPLA) to the [Laryngeal Mask Airway (LMA)-Classic] during gynecological laparoscopy.

METHODS

Forty patients received either an LMA-Classic or a CobraPLA. Insertion, ventilation and removal characteristics were noted, as well as any throat morbidity.

RESULTS

Devices were similar for insertion characteristics, adverse events, and throat morbidity. Before pneumoperitoneum, peak airway pressures were 20.3 +/- 4.9 cm H2O in the LMA-Classic group versus 25.5 +/- 7.9 cm H2O in the CobraPLA group, P = 0.01. This difference was maintained during pneumoperitoneum; LMA-Classic (22.8 +/- 6.1 cm H2O) and CobraPLA (28.1 +/- 8.5 cm H2O), P = 0.04. Macroscopic blood occurred only on the CobraPLA, seen on 40% of the devices after removal, P = 0.001.

CONCLUSION

During gynecological laparoscopy, the CobraPLA provides similar insertion characteristics, but higher airway sealing pressures than the LMA-Classic. The usefulness of this finding requires further investigation.