CJA
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Abstract Freely available
Right arrow Résumé de cet Article
Right arrow Full Text (PDF)
Right arrow Additional Material
Right arrow Submit a scholarly reply
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by O’Connor, C. J.
Right arrow Articles by Valade, D. R.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by O’Connor, C. J., Jr
Right arrow Articles by Valade, D. R.
Canadian Journal of Anesthesia 52:199-204 (2005)
© Canadian Anesthesiologists' Society, 2005
Cardiothoracic Anesthesia, Respiration and Airway

Glottic insertion of the ProSealTM LMA occurs in 6% of cases: a review of 627 patients

[L’insertion glottique du ML ProSealTM survient dans 6 % des cas : une revue de 627 patients]

Cornelius J. O’Connor, Jr, MD, Michael S. Stix, MD PhD and Dennis R. Valade, CRNA

From the Department of Anesthesiology, Lahey Clinic, Burlington, Massachusetts, USA.

Address correspondence to: Dr. Michael S. Stix, Department of Anesthesiology, Lahey Clinic, 41 Mall Road, Burlington, MA 01805, USA. Phone: 781-744-8132, Anesthesiology Department; 781-744-3140 (voice mail); Fax: 781-744-2273; E-mail: michael.stix{at}lahey.org


   Abstract
TOP
 Abstract
Introduction
 Methods
 Results
 Discussion
 References
 
Purpose: Glottic insertion of the ProSealTM Laryngeal Mask Airway (PLMA) has received little attention in the anesthesiology literature. We investigated the incidence and depth of insertion associated with this important cause for a failed insertion attempt with the PLMA.

Methods: With Institutional Review Board approval, we reviewed 15-months’ use of the PLMA. Diagnosis of glottic insertion involved a test with children’s bubble solution placed on the drain tube port, as well as a fibreoptic examination of the airway of patients experiencing airway obstruction. Patients were anesthetized and paralyzed and the PLMA was inserted deflated with the fingertip method (women size 4, men size 5). The cuff was inflated and a soap membrane established on the drain tube port. Glottic insertion was diagnosed by applying fingertip pressure to the patient’s chest wall and observing pulmonary exhalation via the drain tube and bubble formation. The PLMA was then removed and reinserted without further assessment. For all patients, we used a fibrescope to determine the cause of unexplained airway obstruction after the PLMA was considered successfully inserted.

Results: There were 627 patients (391 women, 236 men). We diagnosed glottic insertion in 38/627 (6.1%) patients, 37 by the soap membrane test and one with airway obstruction and direct fibreoptic visualization of malposition. Following glottic insertion, successful reinsertion of the PLMA behind the larynx was always associated with greater depth of insertion by an average 2.0 cm.

Conclusion: Glottic insertion can be easily and quickly diagnosed and our results suggest the incidence and importance of malposition are under-reported in the literature.


   Introduction
TOP
 Abstract
 Introduction
Methods
 Results
 Discussion
 References
 
AN important malposition of the ProSealTM Laryngeal Mask Airway (PLMA) (Laryngeal Mask Company, Henley-on-Thames, UK) discussed in the introductory article and instruction manual is glottic insertion.1,2 This describes unsuccessful insertion of the PLMA during which the tip of the mask enters and then obstructs the laryngeal vestibule. As shown by the fibreoptic image in Figure 1Go, the drain tube orifice at the leading edge of the PLMA then merges end-to-end with the glottis and trachea. Rather than entering the esophageal inlet for channelling gastrointestinal contents to the outside, the drain tube acts as an extension of the pulmonary tract with this malposition. When positive pressure ventilation is attempted using the PLMA the patient experiences upper airway obstruction. Such upper airway obstruction worsens when the mask is pushed inwards because this obstructs the laryngeal inlet further.1,2 The malposition clearly represents an increased risk to the patient for ineffective ventilation and inadequate separation of gastrointestinal and respiratory tracts as intended for a properly positioned PLMA.1



View larger version (64K):
[in this window]
[in a new window]
  		FIGURE 1 Fibreoptic image from the tip of the drain tube during glottic insertion demonstrating view of trachea.

 
Diagnosis of glottic insertion is possible using a soap membrane test, described previously, to detect pulmonary airway pressures in the drain tube.3 We have used this simple test for over two years to rapidly identify insertion attempts resulting in glottic insertion. We have also used a fibrescope for two years to examine unexplained airway obstruction occurring in our patients.4 Here we summarize our regular use of this soap membrane test and fibreoptic examination to report the incidence of glottic insertion of the PLMA.


   Methods
TOP
 Abstract
 Introduction
 Methods
Results
 Discussion
 References
 
Hospital Institutional Review Board approval was obtained for this 15-month retrospective study of PLMA utilization by two physicians (C.J.O. and M.S.S.) from May 2002 through July 2003. We have used the soap membrane test since 2001 and began documenting glottic insertion in our patients at the beginning of May 2002. We used a fibrescope in the operating room regularly from October 2001. Patients were not excluded from PLMA use due to gastroesophageal reflux, hiatal hernia, or obesity.

PLMAs were prepared by careful manual deflation without use of the deflator tool and were lubricated with a water-soluble gel. Patients had an iv induction of anesthesia, ventilation by facemask with 100% oxygen, and neuromuscular blockade. The PLMA was then inserted with the fingertip method,2 using size 4 masks in women and size 5 masks in men, and the cuff inflated to 60 cm H20 (Portex Inc., Cuff Pressure Indicator #660001, Keene, NH, USA).5 Following insertion, we recorded the depth of insertion of the mask with a scoring system comparing positioning of the integral bite block to the upper incisors.6

Using a non-toxic children’s soap bubble solution, a soap membrane was placed on the drain tube by wetting a fingertip and then touching the port.7 Glottic insertion was diagnosed with: 1) large and rapid centimetre-scale oscillation of the soap membrane associated with cardiac pulsation; and 2) formation of a soap bubble from the drain tube following gentle fingertip pressure applied to the patient’s chest wall in the infraclavicular area. The first indication of malposition was the important oscillation of the soap membrane. For complete confidence, however, it was required to observe pulmonary exhalation via the drain tube and bubble formation following fingertip chest compression. Once diagnosed, the PLMA was removed without further assessment and reinserted. Videos demonstrating the soap membrane test and glottic insertion of the PLMA are available as Additional Material on the Journal’s website (www.cja-jca.org).

Next, we tested a second common malposition of the PLMA – foldover of the tip of the mask.2,8,9 With a soap membrane on the drain tube port we pressed the patient’s suprasternal notch. If the soap membrane remained entirely flat we determined that the tip of the PLMA was folded backward.9–11 The PLMA was then removed and reinserted. If the membrane bulged while pressing the suprasternal notch, the PLMA was considered satisfactorily positioned and the device was secured in place with tape over both maxillae.10

Because airway obstruction is a common feature with the PLMA,12,13 the anesthesia circuit was then attached and airway patency carefully assessed. We judged feel of the anesthesia bag and slowed-refilling,14 assessed chest rise and fall, listened for stridor, examined the capnograph, and measured maximum minute ventilation.4 Whenever significant upper airway obstruction was present, we performed a fibreoptic endoscopy. All changes in airway management and adverse perioperative complications attributable to the PLMA were recorded.

Incidences of glottic insertion were contrasted for anesthesiologists C.J.O. vs M.S.S. and for women vs men using a 2 x 2 Chi-squared test and considered statistically significant if P < 0.05.


   Results
TOP
 Abstract
 Introduction
 Methods
 Results
Discussion
 References
 
The retrospective study included 627 patients with demographics presented in the TableGo. Glottic insertion occurred in 38/627 (6.1%) patients, 20/391 (5.1%) women and 18/236 (7.6%) men. Incidence of glottic insertion in women was not statistically different from that encountered in men. Incidence of glottic insertion for anesthesiologist C.J.O. was not statistically different from M.S.S. The PLMA was successfully reinserted in all patients except one with repeated glottic insertion; endotracheal intubation was used without complication.


View this table:
[in this window]
[in a new window]
  		TABLE Demographics of 627 patients
 
Most diagnoses of glottic insertion, 37 of 38, were identified with the soap membrane method. The PLMA was simply removed without further assessment and then reinserted. Once the PLMA was considered satisfactorily inserted, we used a fibrescope to diagnose the cause for airway obstruction (in roughly 5% of the 627 patients). During the 15-month study only one patient experienced a severe airway obstruction resulting from glottic insertion of the PLMA diagnosed by fibreoptic examination. Other patients experiencing airway obstruction were all found to have the PLMA situated behind the larynx and cause was usually compression of the laryngeal inlet by the bulky cuff and tip of the mask.

Depth of insertion was measured in 17/20 of the women with glottic insertion and in 15/18 of the men. In each of these patients the glottic insertion depth was subtracted from normal positioning depth after the device was successfully inserted. Normal positioning of the PLMA always had a greater depth of insertion. For women range was 0.8 to 3.1 cm and average was 1.9 cm deeper. For men range was 1.1 to 3.9 cm and average was 2.1 cm deeper.


   Discussion
TOP
 Abstract
 Introduction
 Methods
 Results
 Discussion
References
 
We have presented our clinical findings pertaining to glottic insertion of the PLMA based largely on our regular use of a simple soap-membrane test, supplemented with occasional fibreoptic examination of patients with severe airway obstruction. Although glottic insertion is a relatively uncommon malposition with the ClassicTM LMA,15,16 we found an occurrence during insertion of 6% of cases using the PLMA in anesthetized and paralyzed patients. It is certainly possible that a lack of experience may have contributed to finite incidence of this malposition. We suspect that we are not alone in, occasionally, requiring more than one insertion attempt to place the PLMA successfully. For example, an original article by experienced users of the prototype gastric-LMA encountered a 6.7% failure rate to establish a patent airway within two insertion attempts with the PLMA.17 This failure rate is strikingly similar to our incidence of glottic impaction. Brimacombe and colleagues have also recently documented difficulty using the fingertip and insertion tool techniques with first insertion success rates of only 87% and 84% respectively.11 It would appear that malposition is more common during insertion of the PLMA compared to the ClassicTM LMA. Although effort in an improved insertion technique is warranted, it is just as important for clinicians to understand the common malpositions of the PLMA and means for rapid diagnosis and recognition.

We were interested in the depth of glottic insertion and, due to the absence of centimetre depth markings, we recorded distances with a system observing positioning of the integral bite block compared to the upper incisors.6 We found that glottic insertion occurred at depths that appeared normal and the bite block was always situated between the patient’s teeth. Unlike the foldover malposition where the bite block frequently protrudes entirely from the mouth providing instant diagnosis,6 glottic insertion could not be diagnosed solely by observing insertion depth. However, we did find that when the PLMA was successfully reinserted it achieved a greater depth of insertion by, on average, 2 cm (the approximate height of the cricoid cartilage).18 This provided an important element of feedback related to repeat insertion attempts.

Because the insertion depth can appear normal, the diagnosis of glottic insertion can be difficult and potentially confusing. The bite block is between the teeth, yet the patient experiences near complete upper airway obstruction when positive pressure ventilation is attempted. In the absence of muscle relaxation it can easily be mistaken for laryngospasm. Little gas appears to reach the lungs, capnography fails to display evidence of gas exchange, and there is absence of chest rise and fall. Pushing the mask inwards does not improve the situation. Passage of a fibrescope through the airway tube characteristically demonstrates a shallower than normal depth of insertion with excessive view of the base of the tongue and tip of the epiglottis visible in the distance draped over on top of the distal drain tube (videos available as Additional Material at www.cja-jca.org). Negotiating the fibrescope under the epiglottis shows the tip of the PLMA obstructing the entire laryngeal vestibule. Alternatively, passage of the fibrescope through the drain tube shows the drain tube emerging at the glottis and trachea.

Once we realized that the soap membrane test provided an easy and rapid diagnosis of glottic insertion, and after many confirmations of this malposition using a fibrescope, we soon began relying on this test completely during initial assessment of PLMA positioning. We simply removed the device without further testing and immediately began preparations for another insertion attempt. After gaining confidence, there was little temptation to spend time confirming the diagnosis by proving airway obstruction or passing a fibrescope. In addition, we frequently found that it could take three to five more insertion attempts before we were successful and assessment of airway patency following each attempt was inefficient. We can be criticized, therefore, for relying so heavily on a blind test for glottic insertion without even testing airway patency to determine positioning of the PLMA. In all cases hindsight assured us of proper judgement; successful reinsertion made the soap membrane signs disappear and the depth of insertion was noted to increase.

One subtlety of the soap membrane test deserves discussion with the help of Figure 2Go. Occasionally, following insertion of the PLMA the esophagus can be found to be "open," as opposed to the usual state where it is "closed" and completely collapsed as a virtual space. The incidence of an open esophagus has been quoted to range between 3 to 9%.19,20 Both "open" and "closed" views of the esophagus are shown in Figure 2Go. When the esophagus is "open" and a soap membrane is positioned on the drain tube the membrane shows large up and down oscillations. This occurs because cardiac contractions distort the esophageal lumen and drive esophageal air up and down the drain tube. A similar effect occurs with glottic insertion when cardiac pulsations drive tracheal gases up and down in the drain tube. Large oscillations of the soap membrane therefore characterize both an open esophagus as well as a glottic insertion. To distinguish one from the other it is necessary to observe pulmonary exhalation via the drain tube and formation of a soap bubble. This is an easy test, pressing gently on the patient’s chest wall with one or two fingers in the infraclavicular area, and watching for bubble formation. Bubble formation occurs with glottic insertion and not with an open esophagus.



View larger version (90K):
[in this window]
[in a new window]
  		FIGURE 2 Fibreoptic views from the tip of the drain tube during normal positioning demonstrating both "closed" and "open" states of esophageal lumen.

 
Another subtlety of the soap membrane test involves use of neuromuscular blockade. As described, we used these drugs in all of our patients. However, if a clinician does not use these drugs laryngospasm can occur. Laryngospasm would make the soap membrane diagnosis of glottic insertion difficult.

We have described use of a soap membrane test using the drain tube to diagnose glottic insertion of the PLMA. The drain tube size is considerable, comparable to a 6.0 or 7.0 mm internal diameter endotracheal tube for a size 4 and 5 PLMA respectively, and it is important to realize its role in diagnosis of PLMA malpositioning. In addition to the soap membrane method there are at least two other simple tests of the drain tube that offer quick diagnosis of glottic insertion. We have used a self-inflating bulb21 illustrated in Figure 3Go, to confirm glottic insertion of the PLMA. With normal positioning of the PLMA the bulb injects easily and then remains collapsed whereas during glottic insertion the bulb injects easily and re-inflates. The self-inflating bulb technique has been described previously for use with a supraglottic airway device, the esophageal tracheal CombitubeTM (Kendall-Sheridan Catheter Corp., Argyle, NY, USA).22 Another simple method involves a TrachlightTM (Laerdal Medical, Wappingers Falls, NY, USA) with stylet removed passed via the drain tube, a technique recently described to diagnose the foldover malposition.23 Just as for blind endotracheal intubation, the TrachlightTM could provide means to quickly distinguish glottic from esophageal location of the tip of the PLMA mask. The drain tube therefore provides a minimum of three simple options to diagnose glottic insertion – 1) soap membrane, 2) self-inflating bulb, and 3) TrachlightTM – all without resorting to a ventilatory trial. We have most experience and most confidence with the soap membrane method but all three techniques should be worthy of consideration.



View larger version (125K):
[in this window]
[in a new window]
  		FIGURE 3 Use of self-inflating bulb. With normal positioning of the ProSealTM laryngeal mask airway the bulb injects easily and then remains collapsed, as shown. With glottic insertion the bulb re-inflates.

 
In summary, we used the PLMA during 15 months in 627 patients and a simple soap membrane test to document insertion attempts resulting in glottic impaction. Glottic insertion occurred in 6% of cases and represents the largest reported incidence of such malposition to date in the anesthesia literature. It is important for clinicians to understand the common malpositions of the PLMA and simple means for rapid diagnosis and recognition.


   Footnotes
 
Assessed May 3, 2004. Accepted for publication September 2, 2004. Revision accepted November 8, 2004.


   References
TOP
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
1 Brain AI, Verghese C, Strube PJ. The LMA ‘ProSeal’ –a laryngeal mask with an oesophageal vent. Br J Anaesth 2000; 84: 650–4.[Abstract/Free Full Text]

2 Anonymous. LMA ProSealTM/LMA FlexibleTM/LMA ClassicTM/LMA UniqueTM Instruction Manual, Revised 2003. San Diego, CA: LMA North America; 2003.

3 O’Connor CJ Jr, Stix MS. Bubble solution diagnoses ProSealTM insertion into the glottis (Letter). Anesth Analg 2002; 94: 1671.[Free Full Text]

4 Stix MS, O’Connor CJ Jr. Maximum minute ventilation test for the ProSealTM laryngeal mask airway. Anesth Analg 2002; 95: 1782–7.[Abstract/Free Full Text]

5 Kihara S, Brimacombe J. Sex-based ProSealTM laryngeal mask airway size selection: a randomized crossover study of anesthetized, paralyzed male and female adult patients. Anesth Analg 2003; 97: 280–4.[Abstract/Free Full Text]

6 Stix MS, O’Connor CJ Jr. Depth of insertion of the ProSealTM laryngeal mask airway. Br J Anaesth 2003; 90: 235–7.[Abstract/Free Full Text]

7 O’Connor CJ Jr, Stix MS. Place the bubble solution with your fingertip (Letter). Anesth Analg 2002; 94: 763.[Free Full Text]

8 Brimacombe J, Keller C, Berry A. Gastric insufflation with the ProSeal laryngeal mask. Anesth Analg 2001; 92: 1614–5.[Free Full Text]

9 Brimacombe J, Keller C. Aspiration of gastric contents during use of a ProSealTM laryngeal mask airway secondary to unidentified foldover malposition. Anesth Analg 2003; 97: 1192–4.[Abstract/Free Full Text]

10 O’Connor CJ Jr, Borromeo CJ, Stix MS. Assessing ProSeal laryngeal mask positioning: the suprasternal notch test (Letter). Anesth Analg 2002; 94: 1374.[Free Full Text]

11 Brimacombe J, Keller C, Judd DV. 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.[Medline]

12 Brimacombe J, Richardson C, Keller C, Donald S. Mechanical closure of the vocal cords with the laryngeal mask airway ProSealTM. Br J Anaesth 2002; 88: 296–7.[Abstract/Free Full Text]

13 Natalini G, Rosano A, Lanza G, Martinelli E, Pletti C, Bernardini A. Resistive load of laryngeal mask airway and ProSealTM laryngeal mask airway in mechanically ventilated patients. Acta Anaesthesiol Scand 2003; 47: 761–4.[Medline]

14 Stix MS, Rodriguez-Sallaberry FE, Cameron EM, Teague PD, O’Connor CJ Jr. Esophageal aspiration of air through the drain tube of the ProSealTM laryngeal mask. Anesth Analg 2001; 93: 1354–7.[Abstract/Free Full Text]

15 Brimacombe J, Berry A. Insertion of the laryngeal mask airway – a prospective study of four techniques. Anaesth Intensive Care 1993; 21: 89–92.[Medline]

16 Brimacombe J. Analysis of 1500 laryngeal mask uses by one anaesthetist in adults undergoing routine anaesthesia. Anaesthesia 1996; 51: 76–80.[Medline]

17 Agro F, Antonelli S, Cataldo R, Montecchia F, Barzoi G, Petitti T. The ProSeal laryngeal mask airway: fibre-optic visualization of the glottic opening is associated with ease of insertion of the gastric tube. Can J Anesth 2002; 49: 867–70.[Abstract/Free Full Text]

18 Williams PL, Warwick R, Dyson M, Bannister LH. Gray’s Anatomy, 37th ed. London: Churchill Livingstone; 1989: 1251.

19 Brimacombe J, Keller C. The ProSeal laryngeal mask airway. A randomized, crossover study with the standard laryngeal mask airway in paralyzed, anesthetized patients. Anesthesiology 2000; 93: 104–9.[Medline]

20 Brimacombe J, Keller C, Fullekrug B, et al. A multicenter study comparing the ProSealTM with the ClassicTM laryngeal mask airway in anesthetized, nonparalyzed patients. Anesthesiology 2002; 96: 289–95.[Medline]

21 Finucane BT, Santora AH. Principles of Airway Management, 3rd ed. New York: Springer-Verlag; 2003: 196–8.

22 Wafai Y, Salem MR, Baraka A, Joseph NJ, Czinn EA, Paulissian R. Effectiveness of the self-inflating bulb for verification of proper placement of the esophageal tracheal Combitube®. Anesth Analg 1995; 80: 122–6.[Abstract]

23 Christodoulou C. ProSeal laryngeal mask foldover detection (Letter). Anesth Analg 2004; 99: 312.[Free Full Text]




This article has been cited by other articles:


Home page
 Br J AnaesthHome page
T. M. Cook and B. Gibbison
Analysis of 1000 consecutive uses of the ProSeal laryngeal mask airwayTM by one anaesthetist at a district general hospital
Br. J. Anaesth., September 1, 2007; 99(3): 436 - 439.
[Abstract] [Full Text] [PDF]

Home page
 Canadian J. AnesthesiaHome page
L. W. Lee
Insertion of the LMA ProSealTM using the Satin-Slip(R) intubating stylet
Can J Anesth, January 1, 2007; 54(1): 81 - 82.
[Full Text] [PDF]

Home page
 Canadian J. AnesthesiaHome page
W. A. C. Mutch
Facilitated insertion of the ProSealTM laryngeal mask airway using a lightwand.
Can J Anesth, June 1, 2006; 53(6): 635 - 636.
[Full Text] [PDF]

Home page
 Canadian J. AnesthesiaHome page
K. J. Chin and V. W.T. Chee
Laryngeal edema associated with the ProSealTM laryngeal mask airway in upper respiratory tract infection: [OEdeme larynge associe au masque larynge ProSealTM dans une infection des voies respiratoires superieures].
Can J Anesth, April 1, 2006; 53(4): 389 - 392.
[Abstract] [Full Text] [PDF]

Home page
 Canadian J. AnesthesiaHome page
T. Cook
Optimizing insertion of the ProSeal laryngeal mask airway
Can J Anesth, October 1, 2005; 52(8): 885 - 886.
[Full Text] [PDF]

Home page
 Canadian J. AnesthesiaHome page
T. M. Cook, G. Lee, and J. P. Nolan
The ProSealTM laryngeal mask airway: a review of the literature: [Le masque larynge ProSealTM : un examen des publications]
Can J Anesth, August 1, 2005; 52(7): 739 - 760.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Résumé de cet Article
Right arrow Full Text (PDF)
Right arrow Additional Material
Right arrow Submit a scholarly reply
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by O’Connor, C. J.
Right arrow Articles by Valade, D. R.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by O’Connor, C. J., Jr
Right arrow Articles by Valade, D. R.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS