BJA Advance Access originally published online on November 25, 2005
British Journal of Anaesthesia 2006 96(2):238-241; doi:10.1093/bja/aei290
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PAEDIATRIC ANAESTHESIA |
Bougie-guided insertion of the ProSealTM laryngeal mask airway has higher first attempt success rate than the digital technique in children
1 Department of Anaesthesia and Reanimation, Maranon University Hospital, Madrid, Spain. 2 Department of Anaesthesia and Intensive Care, Cairns Base Hospital, Cairns, Australia. 3 Department of Anaesthesia and Intensive Care Medicine, Medical University, Innsbruck, Austria
* Corresponding author: Department of Anaesthesia and Intensive Care, Cairns Base Hospital, The Esplanade, Cairns 4870, Australia. E-mail: jbrimaco{at}bigpond.net.au
Accepted for publication October 26, 2005.
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Abstract |
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Background. We tested the hypothesis that bougie-guided insertion of the ProSealTM laryngeal mask airway (ProSealTM LMA) has higher success rate than the digital technique in children.
Methods. One hundred and twenty children (ASA I–II, aged 1–16 yr) were randomly allocated for ProSealTM LMA insertion using the digital or bougie-guided technique. The digital technique was performed according to the manufacturer's instructions. The bougie-guided technique involved priming the drain tube with a bougie, placing the bougie in the oesophagus under direct vision and railroading the ProSealTM LMA into position. Unblinded data were collected about ease of insertion (number of attempts and time taken to provide an effective airway), efficacy of seal, ease of gastric tube placement, haemodynamic responses and blood staining. Blinded data were collected about postoperative airway morbidity.
Results. The first attempt success rate was higher for the bougie-guided technique (59/60 vs 52/60, P=0.015), but effective airway time was longer (37 vs 32 s, P<0.001). There were no differences in efficacy of seal, ease of gastric tube placement, haemodynamic responses, blood staining or postoperative airway morbidity.
Conclusion. We conclude that bougie-guided insertion of the ProSealTM LMA has a higher first attempt success rate than the digital technique in children.
Keywords: airway, technique; complications, children; equipment, ProSealTM laryngeal mask airway
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Introduction |
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The ProSealTM laryngeal mask airway (ProSealTM LMA) is a relatively new laryngeal mask device with a modified cuff to improve the seal and a drain tube to prevent aspiration and gastric insufflation.1 The manufacturer recommends inserting the ProSeal LMA using digital manipulation, like the ClassicTM LMA, or with an introducer tool, like the IntubatingTM LMA.2 However, an adult study showed that guiding the ProSealTM LMA into position along a gum elastic bougie placed in the oesophagus under pharyngoscopy with the aid of a laryngoscope was more frequently successful.3 In the following prospective randomized study, we have tested the hypothesis that bougie-guided insertion of the ProSealTM LMA is more frequently successful than the digital technique in children.
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Methods |
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One hundred and twenty ASA I–II children, aged 1–16 yr and weighing 10–50 kg, undergoing minor non-head and neck surgery in the supine position were randomized for ProSealTM LMA insertion using either digital or bougie-guided technique. Equal numbers of both the sexes (30 males and 30 females) and equal numbers of ProSealTMLMA sizes (20 size 2, 20 size 2.5, 20 size 3) were used in each group. Randomization was by opening an opaque sealed envelope. Ethical committee approval and written parental consent were obtained. Patients were excluded if they had a known or predicted difficult airway or were at risk of aspiration. All patients were managed by experienced LMA users with >30 uses with each technique.
Patients were fasted for at least 6 h for solids and 4 h for liquids. Premedication was with midazolam 0.5 mg kg–1 given orally 30 min before induction of anaesthesia. A standard anaesthesia protocol was followed and routine monitoring applied, including an ECG, pulse oximeter, gas analyzer, noninvasive blood pressure monitor, tidal volume monitor and airway pressure monitor. Patients underwent either i.v. induction of anaesthesia with propofol 3 mg kg–1 or inhalational induction with sevoflurane 8%, according to the preference of the clinician. Following induction, face mask ventilation was performed using sevoflurane 2–4% in oxygen until conditions were suitable for ProSealTM LMA insertion (apnoea and lack of response to jaw thrust4). The sizes 2, 2.5 and 3 were used in children weighing 10–20, >20–30 and >30–50 kg, respectively.
The digital insertion technique was performed according to the manufacturer's instructions and involved the use of the index finger to press the ProSealTM LMA into, and advance it around, the palatopharyngeal curve.2 For the bougie-guided technique, the drain tube of the ProSealTM LMA was primed with a lubricated bougie with its straight end first, leaving the 5 cm bent portion protruding from the proximal end (for the assistant to grip), and the maximum length protruding from the distal end (for the anaesthesiologist to manipulate). The bougie-guided technique involved the following steps: (i) under pharyngoscopy with the aid of a laryngoscope, the distal portion of the bougie was placed 5 cm into the oesophagus while the assistant held the ProSealTM LMA and proximal portion; (ii) the laryngoscope was removed; (iii) the ProSealTM LMA was inserted using the digital insertion technique while the assistant stabilized the proximal end of the bougie so it did not penetrate further into the oesophagus; and (iv) the bougie was removed while the ProSealTM LMA was held in position.5 All techniques were performed in the sniffing position with the cuff fully deflated and using a midline or slight lateral approach. Once the ProSealTM LMA was inserted into the pharynx, the cuff was inflated with air until effective ventilation was established or the maximum recommended inflation volume was reached. Fixation was according to the manufacturer's instructions.2 A well-lubricated 60 cm long gastric tube (10F for size 2; 12F for size 2.5; 14F for size 3) was inserted through the drain tube if there was no air leak up the drain tube. Correct gastric tube placement was assessed by suction of fluid or detection of injected air by epigastric stethoscopy.6
Three attempts were allowed before insertion was considered a failure. Failed insertion was defined by any of the following criteria: (i) oropharyngeal impaction (failed passage into the pharynx); (ii) glottic impaction (airway obstruction, mid-portion of bite block protruding from the mouth7); (iii) mechanical airway obstruction (airway obstruction, mid-portion of bite block between teeth, no improvement with propofol); (iv) reflex airway obstruction (airway obstruction, mid-portion of bite block between the teeth, improvement with propofol); (v) folding over of the cuff (clear airway, mid-portion of bite block protruding from mouth, failure to insert the gastric tube); and (vi) inadequate seal (clear airway, mid-portion of bite block between teeth, low airway pressure oropharyngeal air leaks). The time between picking up the laryngoscope or prepared ProSealTM LMA (cuff deflated, lubricated, guide attached) and successful placement was recorded. The aetiology of failed insertion was documented. If insertion failed after three attempts, a single attempt was permitted with the alternative technique. Once insertion was successful, the intracuff pressure was set at 60 cm H2O using a digital manometer (Mallinckrodt Medical, Athlone, Ireland) and the oropharyngeal leak pressure was determined up to a maximum of 40 cm H2O.8 Heart rate and mean blood pressure were recorded 1 min before and 1 min after insertion. Any episodes of hypoxia (SpO2<90%) or other adverse events were documented. Any visible blood staining on the guide, laryngoscope, or ProSealTM LMA was noted at removal. The mouth, lips and tongue were inspected for evidence of trauma.
Patients and their parents underwent a structured interview 18–24 h after surgery. Patients/parents were asked about sore throat (constant pain, independent of swallowing), dysphonia (difficulty/pain on speaking) and dysphagia (difficulty/pain on swallowing). Symptoms were graded by the patient as mild, moderate or severe. Patients and/or parents were unaware of the insertion technique used. Unblinded trained observers collected the data during anaesthesia and a blinded trained observer collected the data the following day.
Sample size was based upon a projected difference of 10% between the groups for first attempt success rate, a type I error of 0.05 and a power of 0.9, and was based on a study comparing the digital and bougie-guided technique in adults.3 If the randomized device failed, all variables (other than oropharyngeal leak pressure) were assigned to the initial randomized device (intention to treat). The distribution of data was determined using Kolmogorov–Smirnov analysis.9 Statistical analysis was with two-tailed unpaired t-test and 
2-test. Data are given as mean (SD) unless otherwise stated. Significance was taken at P<0.05.
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Results |
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All data are presented in Table 1. There were no demographic differences and the ratio of i.v. to gaseous induction of anaesthesia was similar. The first attempt success rate was higher for the bougie-guided technique (P=0.015), but effective airway time was longer (P<0.0001). The aetiology of failed insertion with the digital technique was oropharyngeal impaction in two patients and glottic impaction in six patients. The aetiology of failed insertion with the bougie-guided technique was resistance at the level of the hypopharynx during placement of the bougie (n=1). There were no differences in oropharyngeal leak pressure, number of attempts for gastric tube insertion and blood straining. The aetiology of failed insertion of the gastric tube was inadequate lubrication in all patients. In seven patients, there was a trace of blood on the laryngoscope and bougie, which was associated with minor injuries to the lip, mouth or tonsils caused by the laryngoscope. There were no differences in postoperative airway morbidity. There were no haemodynamic responses to insertion in either group.
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Discussion |
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The first attempt success rate was higher for the bougie-guided than the digital technique. This is because it directs the distal cuff around the back of the mouth (thereby avoiding oropharyngeal impaction, which occurred in 3% with the digital technique) and into the hypopharynx (thereby avoiding glottic impaction, which occurred in 10% with the digital technique). Our success rates for the digital and bougie-guided technique were similar to previous studies in children10 11 and adults,3–5 respectively. Interestingly, O'Connor and colleagues12 found that the frequency of glottic impaction was 6% in adults using non-guided techniques. Obtaining an effective airway took slightly longer with the bougie-guided technique; however, we consider the additional 5 s to be clinically unimportant.
A major advantage of the bougie-guided technique is that it prevents the cuff folding over, which is the most dangerous of the ProSealTM LMA malpositions, as it is compatible with a clear airway and a good seal but the drain tube is occluded, which puts the patient at risk of aspiration13 and gastric insufflation.14 Another advantage is that gastric tube insertion rarely fails, as the drain tube and oesophagus are in alignment. Our high failure rate for gastric tube placement was due to inadequate lubrication. There is a very high coefficient of friction between silicone (drain tube) and plastic (gastric tube). Yet another advantage is that diagnosing the aetiology of subsequent ventilatory failure is easier, as malposition of the distal cuff can be eliminated from the list of possible causes.
The disadvantages of the bougie-guided technique are the potential for stimulation and trauma. However, there were no episodes of airway protective reflex activation, and there were no differences in haemodynamic responses, blood staining or postoperative airway morbidity. This is because only slight force is needed to view the hypopharynx compared with the larynx. In fact, ‘pharyngoscopy’ is a better word than ‘laryngoscopy’ to describe the viewing requirements for the bougie-guided technique. Avoiding force during insertion of the laryngoscope and passage of the bougie should reduce the risk of trauma. Interestingly, in the adult study3 the bougie-guided technique was found to be less traumatic than the digital technique, as evidenced by a lower frequency of occult blood, which was probably related to the lack of oropharyngeal impaction and the need for fewer insertion attempts. We have used it on over 10 000 occasions in mostly adults without any major complications. However, until further data are available perhaps bougie-guided technique should be used as a backup when the digital or introducer techniques fail. A bougie will soon be available which has an atraumatic distal portion to further reduce risk.
Our study has several limitations. First, all the devices were inserted by experienced personnel and our data may not be applicable to those with less experience. However, we consider that the digital technique requires more skill than the bougie-guided technique, and that anaesthesiologists with laryngoscope skills but little experience with the ProSealTM LMA will have a higher success rate with the bougie-guided technique. Second, we did not include a group where the ProSealTM LMA was inserted using laryngoscope-guidance, but without bougie-guidance. In principle, laryngoscopy might have improved insertion conditions by widening the pharynx even after removal; however, we consider this unlikely. Fourth, we did not include a group where the ProSealTM LMA was inserted using the introducer tool and it is possible that this might be more successful than the digital technique; however, the success rate for the digital and introducer tool techniques are similar in adults3 and with similar causes of failure.15 We consider it likely that the bougie-guided technique will be better than the introducer tool technique in children. Fifth, although we detected no differences in insertion success between males and females or among different sizes of ProSealTM LMA, the study was not sufficiently powered to be confident of these results. Finally, there was no blinding in the intraoperative data collection, a possible source of bias.
We conclude that bougie-guided insertion of the ProSealTM LMA has a higher first attempt success rate than the digital technique in children.
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Acknowledgments |
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This project was supported solely by departmental resources.
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Footnotes |
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Declaration of interest. Dr Brimacombe and Dr Keller have worked as consultants for the Laryngeal Mask Company, who manufacture ProSealTM LMA. 
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References |
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1 Brain AIJ, Verghese C, Strube PJ. The LMA ‘ProSeal’—a laryngeal mask with an oesophageal vent. Br J Anaesth 2000; 84: 650–4
2 LMA. LMA ProSealTM Instruction Manual, 1st edn. San Diego: LMA North America Inc, 2000
3 Brimacombe J, Keller C, Vosoba Judd D. Gum elastic bougie-guided insertion of the ProSealTM laryngeal mask airway is superior to the digital and introducer tool techniques. Anesthesiology 2004; 100: 25–9[CrossRef][Web of Science][Medline]
4 Drage MP, Nunez J, Vaughan RS, Asai T. Jaw thrusting as a clinical test to assess the adequate depth of anaesthesia for insertion of the laryngeal mask. Anaesthesia 1996; 51: 1167–70[Web of Science][Medline]
5 Howarth A, Brimacombe J, Keller C. Gum elastic bougie-guided insertion of the ProSeal laryngeal mask airway. A new technique. Anaesth Intensive Care 2002; 30: 624–7[Web of Science][Medline]
6 Brimacombe J, Keller C, Kurian S, Myles J. Reliability of epigastric auscultation to detect gastric insufflation. Br J Anaesth 2002; 88: 127–9
7 Stix MS, O'Connor CJ. Depth of insertion of the ProSealTM laryngeal mask airway. Br J Anaesth 2003; 90: 235–7
8 Keller C, Brimacombe J, Keller K, Morris R. A comparison of four methods for assessing airway sealing pressure with the laryngeal mask airway in adult patients. Br J Anaesth 1999; 82: 286–7
9 Gaddis GM, Gaddis ML. Introduction to biostatistics: part 5, statistical inference techniques for hypothesis testing with nonparametric data. Ann Emerg Med 1990; 19: 1054–9[CrossRef][Web of Science][Medline]
10 Lopez-Gil M, Brimacombe J. The ProSeal laryngeal mask airway in children. Paediatr Anaesth 2005; 15: 229–34[Medline]
11 Shimbori H, Ono K, Miwa T, Morimura N, Noguchi M, Hiroki K. Comparison of the LMA-ProSeal and LMA-Classic in children. Br J Anaesth 2004; 93: 528–31
12 Brimacombe J. Other extraglottic devices. In: Laryngeal Mask Anesthesia. Principles and Practice. London: WB Saunders, 2005; 577–632
13 Brimacombe J, Keller C. Aspiration of gastric contents during use of a ProSeal laryngeal mask airway secondary to unidentified foldover malposition. Anesth Analg 2003; 97: 1192–4
14 Brimacombe J, Keller C, Berry A. Gastric insufflation with the ProSeal laryngeal mask. Anesth Analg 2001; 92: 1614–15
15 Brimacombe J, Keller C. Gum elastic bougie-guided insertion of the ProSealTM laryngeal mask airway. Anaesth Intensive Care 2004; 32: 681–4[Web of Science][Medline]
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