BJA Advance Access published online on June 29, 2007
British Journal of Anaesthesia, doi:10.1093/bja/aem172
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Analysis of 1000 consecutive uses of the ProSeal laryngeal mask airwayTM by one anaesthetist at a district general hospital
Royal United Hospital, Combe Park, Bath BA1 3NG, UK
* Corresponding author. E-mail: timcook007{at}googlemail.com
Accepted for publication May 6, 2007.
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Abstract |
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Background: The ProSeal laryngeal mask airway (PLMA), introduced to UK practice in late 2001, offers potential performance and safety benefits over other airways such as the classic laryngeal mask airway. There are no large series reporting its use.
Methods: Data from a prospective, consecutive series of 1000 size 3–5 PLMA uses, by one anaesthetist, were analysed to examine whether performance in routine and advanced practice is similar to that reported in formal trials.
Results: Patients were female in 52% of cases, median age 52 (range 8–101) yr, median weight 78 kg (10% over 100 kg, 24% over 90 kg). Procedures included 12% laparoscopic and 5% open abdominal surgery. Overall insertion success was 99.4%, (first and second attempt success 85% and 12%, respectively). Median insertion time was 12 s (93% <30 s). Insertion success did not differ between genders, or between mask sizes. Median airway seal was 32 cm H2O (range 8–40, 94% seal >20 cm H2O). Specific tests confirmed correct positioning in 98.5% of cases. Of six failures, two occurred during management of difficult airways. Minor airway obstruction occurred in 2.7%. Blood was visible on 8% of removed PLMAs and more commonly after more than one insertion attempt (38 vs 4.7%, 
2 P<0.0001). In three cases minor regurgitation without aspiration occurred.
Conclusions: In the hands of a regular user, the PLMA was associated with a high rate of insertion success during routine and advanced use in relatively unselected patients. Correct placement rates approached 100%. The incidence of complications was low.
Keywords: anaesthesia, audit; equipment, airway; equipment, masks anaesthesia
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Introduction |
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The ProSealTM laryngeal mask airway (PLMA) (Intavent Orthofix, Maidenhead, UK) was introduced into UK practice in 2001 (Fig. 1). It is similar in basic structure to the classic laryngeal mask airway (cLMA) with modifications designed to separate the respiratory and gastro-intestinal tract, improve airway seal, improve safety and efficacy of controlled ventilation, and enable diagnosis of misplacement.1 The modifications are:1
- A larger and deeper mask bowl with no bars.
- A posterior extension of the mask cuff.
- A drainage tube (DT) running parallel to the airway tube and exiting at the mask tip. This enables passage of an orogastric tube to allow drainage of stomach contents. The DT also enables a number of tests to be performed that confirm correct placement or diagnose the nature of misplacement. Among these tests misplacement of the tip either through folding over or placement into the glottis can be detected by firm tapping on the suprasternal notch or pressure on the chest, respectively.
- An integral, silicone bite block.
- An anterior pocket for seating an introducer or finger during insertion.
- The mask bowl lacks the ‘semi-rigid shell’ of the cLMA.
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These design features are expected to reduce gastric inflation, regurgitation, and subsequent pulmonary aspiration when compared with the cLMA.1 Earlier reports under study conditions have shown that the PLMA has a high success rate of insertion (first attempt 87.3%, overall 98.4%),2 although a greater depth of anaesthesia is required for placement of the PLMA compared with the cLMA.3 Average airway seal pressures have been found to be consistently about 50% higher than with the cLMA4 with most authors reporting an average seal pressure of 28–32 cm H2O.2 Under study conditions, mucosal damage from the PLMA, indicated by blood on the cuff at removal, ranges from 3 to 28% (mean 10.8%) of cases. This is similar or below levels quoted for the cLMA.2
There are no large series in the literature reporting performance or safety of use of the PLMA during routine practice. Most data come from studies in which higher risk patients will have been excluded. We have therefore examined the performance of the PLMA in a series of cases, in routine clinical practice, in a less selected population.
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Methods |
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The first author's personal database was interrogated for all general anaesthetic cases in which a PLMA was used or its use attempted. Patient age, gender, weight, operation, number of attempts, and time to placement (from observation of the theatre clock), misplacements, peak airway pressures, and airway seal pressure were recorded routinely. Any blood on the mask (representing mucosal damage) and problems encountered were also recorded prospectively. In the last 317 cases of the series formal tests of correct positioning (gel tests) were performed once the PLMA had been successfully placed (Table 1). The series runs from the first use of the device in November 2000 to the 1000th use in January 2007: and represents 35% of the author's adult general anaesthetic cases.
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The insertion techniques used evolved during the course of the series. Initially, only the digital and introducer techniques were used.2 The gum elastic bougie technique was described in October 2002.5 For the latter half of the series the author’s standard practice was to insert the PLMA with the introducer first, digitally if that failed and to consider using a gum elastic bougie assisted technique if this also failed. Controlled ventilation was used routinely but muscle relaxation is used only when considered surgically necessary. For the last 800 cases, PLMA cuff pressure was measrued and maintained at a pressure of 60 cm H2O.
Airway seal pressure is a measure of how well the PLMA fits the airway and was measured with fresh gas flow set at 5 litre min–1 and the airway pressure release valve closed. Airway pressure was allowed to rise until it plateaued or reached 40 cm H2O. Seal pressures were measured using the anaesthetic machine (Datex S/3 or S/5 ADU, Datex–Ohmeda, Madison, WI, USA).
Total i.v. anaesthesia with propofol 1% was used for 95% of cases.
2 testing was used to compare categorical data where appropriate.
Publication of these data was discussed with the Chair of the Research Ethics Committee, who considered this an audit of practice that did not need ethical approval.
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Results |
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Patients
The first author's personal database included 1000 consecutive patients in whom the PLMA was used. Sizes 3–5 were available throughout the data collection period. Fifty-two per cent of patients were female, median patient age was 52 yr (range 8–101 yr) with median weight 78 kg (range 24–150 kg). Ten per cent of patients weighed over 100 kg and 24% over 90 kg. Surgical specialties were general surgery 34.4%, orthopaedics 29.4%, urology 17.6%, gynaecology 11.2%, ENT 5.8%, and ophthalmology and vascular surgery each 0.8%. Most procedures were peripheral or external surgeries but included 12% laparoscopic procedures and 5% open abdominal (mostly gynaecological) procedures.
Insertion success
Successful insertion was achieved on the first attempt on 84.5% (845/1000) occasions, second attempt 12%, third attempt 3.1% and fourth attempt 0.5%. Overall success was 99.4% (994/1000) with PLMA use being abandoned in six cases. Gum elastic bougie-guided insertion was attempted on 12 occasions and failed twice. Median time for PLMA placement (picking up the device to ventilation of lungs) was 12 s with 75% (750/994) of masks placed within 15 s and in 93% (921/994) within 30 s. For women sizes 3, 4, and 5 PLMAs were used in 5%, 92%, and 3% of cases: first time success rates were 76%, 84% and 89% respectively (2 P=0.45). For men sizes 4 and 5 PLMAs were used in 13% and 87% of cases: first time success rates were 94% and 88% respectively (2 P=0.24).
Insertion failures
Of the six failures, all occurred at the time of placement and no PLMA was abandoned intra-operatively, though four required repositioning intra-operatively. Three failures occurred before the gum elastic bougie insertion technique was reported and this technique was not used. In one case of failure, insertion of a cLMA was successful: and tracheal intubation was required on five occasions. Two failures were in patients who had had radiotherapy to the neck and whose airway management was complex.6 7
Pressures
Median airway seal pressure was measured in 996 patients. Median seal pressure was 32 cm H2O (range 8–40). Seal pressure was >12 cm H2O in 99.4%, >20 cm H2O in 94%, >30 cm H2O in 63%, and >40 cm H2O in 24% of cases. Median peak airway pressure during ventilation at 7 ml kg–1 was 15 cm H2O.
Tests of position and malposition
In the last 317 cases of the series, formal tests of correct positioning were performed once the PLMA had been placed. In 98.5% of cases, the mask was clinically correctly placed and all four tests were passed. In two cases, the bite block was protruding but performance was normal, in one the suprasternal notch test was negative but passage of a gastric tube showed this to be a false negative, and in one case hiccoughing led to in-drawing of gel from the drain tube. There were no cases of glottic insertion of the tip of the PLMA.
Problems and complications
Twenty-five (2.7%) cases showed partial airway obstruction. However, this required removal of the device in only one case. Folding over of the PLMA tip required reinsertion in 15 cases (1.7%). It was noted that in patients who moved during PLMA insertion positioning was often imperfect but this was not formally studied. The PLMA was removed and repositioned because of intra-operative problems in four cases (0.4%), due to airway obstruction, which was partial in three cases and complete in one.
Blood (usually minor) was visible on the PLMA at the time of removal in 8% of cases. Blood was more commonly seen when insertion required more than one insertion attempt (42 of 151 cases, 38%) than when successful on the first attempt (38 of 838 cases, 4.7%) (P<0.0001).
In three cases, minor regurgitation without aspiration occurred in elective starved patients. In all cases, the drain tube vented the regurgitant fluid. Fibreoptic and clinical examination confirmed no aspiration had occurred. In one of these cases, 240 ml of fluid was aspirated from the patient's stomach and in another who did not regurgitate, 500 ml was aspirated. One patient developed a hypoglossal nerve palsy after prolonged use of the PLMA, without cuff pressure monitoring.8
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Discussion |
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The authors' data are is the largest series of ProSeal LMA use published to date. Our results indicate that ‘everyday use’ by an experienced PLMA user can be associated with as low a failure rate as reported for the cLMA. First attempt insertion success, overall success, and airway leak pressure are remarkably similar to those reported in the literature.2 Use of the PLMA is associated with lower mucosal damage rates than with the cLMA, in both this series and previously published data.6 The reasons for this are unclear, but may be due to either lower cuff pressures in the PLMA, lack of the semi-rigid shell of the mask bowl reducing trauma on insertion, or the greater volume of the cuff allowing more widespread distribution of pressure effects.9
The use of the Proseal LMA offers clear advantages over the cLMA in certain situations, with little cost in terms of ease of insertion success. There is evidence that the PLMA may also have a useful role as a conduit during the management of patients with difficult airways and for airway rescue (in particular, during rapid sequence induction).10–15
Use of the PLMA is one of the recommendations in the Difficult Airway Society guidelines for management of failed intubation at rapid sequence induction.16 This series, including almost a quarter of patients weighing over 90 kg, whom some would consider inappropriate for management with a CLMA offers some evidence of the safety and clinical utility of the PLMA.
One of Dr Brain's design goals for the PLMA was to design a device that allowed confirmation of correct positioning of the airway and diagnosis of misplacement. In the latter third of this series that goal was achieved. The PLMA was correctly positioned both clinically and according to use of the specific tests in 98.5%. Malpositions were readily diagnosed. Of note, there were no glottic insertions of the PLMA tip, which contrasts with a 6% incidence in a previous report.17
In conclusion, analysis of a large consecutive series of PLMA uses by an experienced user shows that, even when used in a less selected and probably more clinically demanding population than would be studied in clinical trials, its use is associated with a high success rate, high levels of clinical utility, and low rates of complications.
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Footnotes |
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Declaration of interest. Dr Tim Cook has been paid by Intavent Orthofix and the LMA company, both of which manufacture laryngeal masks, for lecturing. Neither company had any involvement in this paper. 
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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 Cook TM, Lee G, Nolan JP. The ProSealTM laryngeal mask airway: a review of the literature. Can J Anesth (2005) 52:739–60.[Web of Science][Medline]
3 Kodaka M, Okamoto Y, Koyama K, Miyao H. Predicted values of propofol EC50 and sevoflurane concentration for insertion of laryngeal mask ClassicTM and ProSealTM. Br J Anaesth (2003) 92:242–5.[CrossRef][Web of Science]
4 Cook TM, Nolan JP, Verghese C, et al. A randomised crossover comparison of the Pro-Seal with the classic laryngeal mask airway in unparalysed anaesthetised patients. Br J Anaesth (2002) 88:527–33.
5 Howarth A, Brimacombe J, Keller C. Gum-elastic bougie-guided insertion of the ProSeal laryngeal mask airway: a new technique. Anaesth Intens Care (2002) 30:624–7.[Web of Science][Medline]
6 Cook TM, Seller C, Gupta K, Thornton M, O'Sullivan E. Non-conventional uses of the Aintree Intubating catheter in management of the difficult airway: fourteen reports. Anaesthesia (2007) 62:169–74.[CrossRef][Web of Science][Medline]
7 Cook TM, Bigwood B, Cranshaw J. A complication of TTJV and use of the Aintree Intubating Catheter during airway resuscitation. Anaesthesia (2006) 61:692–7.[CrossRef][Web of Science][Medline]
8 Trumplemann P, Cook TM. Unilateral hypoglossal nerve injury following use of a ProSeal laryngeal mask. Anaesthesia (2005) 60:101–2.[CrossRef][Web of Science][Medline]
9 Keller C, Brimacombe J. Mucosal pressure and oropharyngeal leak pressure with the ProSeal versus laryngeal mask airway in anaesthetised paralyzed patients. Br J Anaesth (2000) 85:262–6.
10 Craven R, Laver S, Cook TM, Nolan JP. Use of the Proseal LMA facilitates percutaneous tracheostomy. Can J Anaesth (2003) 50:718–20.[Web of Science][Medline]
11 Cook TM, Silsby J, Simpson TP. Airway rescue in acute upper airway obstruction using a ProSealTM Laryngeal mask airway and an Aintree CatheterTM – a review of the ProSealTM Laryngeal mask airway in the management of the difficult airway. Anaesthesia (2005) 60:1129–36.[CrossRef][Web of Science][Medline]
12 Brimacombe J, Keller C. A modified rapid sequence induction using the ProSeal laryngeal mask airway and an Eschmann tracheal tube introducer or gum elastic bougie. Anesthesiology (2004) 101:1251–2.[CrossRef][Web of Science][Medline]
13 Awan R, Nolan JP, Cook TM. Use of the ProSeal LMA for airway maintenance during emergency Caesarean section after failed intubation. Br J Anaesth (2004) 92:144–6.
14 Baxter S, Brooks A, Cook TM. Use of the ProSeal LMA for airway management after failed rapid sequence induction. Anaesthesia (2003) 58:1132–3.[CrossRef][Web of Science][Medline]
15 Cook TM, Brooks TS, Van der Westhuizen J, Clarke M. The ProsealTM LMA is a useful rescue device during failed rapid sequence intubation: two additional cases. Can J Anesth (2005) 52:630–3.[Web of Science][Medline]
16 Henderson JJ, Popat MT, Latto IP, Pearce AC. Difficult Airway Society guidelines for management of the unanticipated difficult intubation. Anaesthesia (2004) 59:675–94.[CrossRef][Web of Science][Medline]
17 O'Connor CJ Jr, Stix MS, Valade DR. Glottic insertion of the ProSeal LMA occurs in 6% of cases: a review of 627 patients. Can J Anaesth (2005) 52:199–204.[Web of Science][Medline]
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