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Canadian Journal of Anesthesia 53:398-403 (2006)
© Canadian Anesthesiologists' Society, 2006
Cardiothoracic Anesthesia, Respiration and Airway

Suction catheter guided insertion of the ProSealTM laryngeal mask airway is superior to the digital technique

[L’insertion du masque laryngé ProSealTM, guidée par une sonde d’aspiration, est supérieure à la technique digitale]

Roberto García-Aguado, MD PhD*, Juan Viñoles, MD{dagger}, Joseph Brimacombe, MB CHB FRCA MD{ddagger}, Miguel Vivó, MD*, Rosario López-Estudillo, MD{dagger} and Guillermo Ayala, PhD§

* From the Servicio Anestesia, Reanimación y Terapeútica del Dolor, Consorcio Hospital General Universitario de Valencia; Valencia; the
{dagger} Servicio Anestesia, Reanimación y Terapeútica del Dolor, Hospital Universitario Dr. Peset, Valencia; the
{ddagger} Department of Anaesthesia and Intensive Care, James Cook University, Cairns Base Hospital, Cairns, Australia; and the
§ Department of Statistics, University of Valencia, Valencia, Spain.

Address correspondence to: Dr. Joseph Brimacombe, Department of Anaesthesia and Intensive Care, Cairns Base Hospital, The Esplanade, Cairns 4870, Australia. E-mail: jbrimaco{at}bigpond.net.au


   Abstract
TOP
 Abstract
Introduction
 Methods
 Results
 Discussion
 References
 
Purpose: We tested the hypothesis that digital insertion of the ProSealTM laryngeal mask airway (ProSealTM LMA) is more successful when using a suction catheter (SC) as a guide.

Methods: Two hundred and forty-three patients (ASA physical status I–III; aged 18–84 yr) were randomly allocated for the digital or SC-guided technique. The digital technique was performed according to the manufacturer’s instructions. The SC technique involved priming the drain tube with the SC so that it protruded by 15 cm, blindly inserting the SC into the pharynx to a depth of 15 cm, followed by the digital technique. Failed insertion was defined by any of the following criteria: 1) failed passage into the pharynx; 2) malposition; and 3) ineffective ventilation. Any airway trauma, and visible or occult blood was noted. Sore throat, dysphonia and dysphagia were assessed 16 to 24 hr postoperatively.

Results: Fewer insertion attempts were required with the SC-guided technique (P = 0.02), but first attempt and overall success were similar. The time taken to provide an effective airway was shorter for the SC-guided technique (36 ± 24 sec vs 44 ± 28 sec, P = 0.02). A lateral approach was required less frequently with the SC-guided technique (0% vs 4%, P = 0.0004). There were no adverse events. Mouth trauma was more frequent with the digital technique (P = 0.04), but overall trauma was similar. There were no differences in the frequency of visible or occult blood. There were no differences in postoperative airway morbidity.

Conclusions: The SC-guided technique is more frequently successful than the digital technique and is associated with less mouth trauma during insertion of the ProSealTM LMA. We suggest that the SC technique may be a useful alternative when the digital technique fails.


   Introduction
TOP
 Abstract
 Introduction
Methods
 Results
 Discussion
 References
 
THE ProSealTM laryngeal mask airway (ProSealTM LMA; Intavent Orthofix, Maidenhead, UK) is a relatively new LMA device with a modified cuff to improve the seal and a drain tube to help prevent aspiration and gastric insufflation, facilitate passage of a gastric tube, and provide information about malposition.1 The manufacturer recommends inserting the ProSealTM LMA using digital manipulation or with an introducer tool, but both these techniques have lower success rates than the classic LMA.2 Four new techniques have recently been described to facilitate insertion; all involve priming the drain tube with a guide that is directed into the proximal esophagus. Our group described the use of a suction catheter (SC);3 Drolet and Girard4 the use of a gastric tube; Brimacombe et al.5 the use of a fibreoptic scope; and Howarth et al.6 the use of a gum elastic bougie. However, only the gum elastic bougie technique has been the subject of a randomized control trial. In this study, we test the hypothesis that the success rate of the ProSealTM LMA insertion is increased when using an SC as a guide.


   Methods
TOP
 Abstract
 Introduction
 Methods
Results
 Discussion
 References
 
Ethical Committee approval and written informed consent were obtained. Two hundred and forty-three patients (ASA physical status I–III, aged 18–84 yr) undergoing ambulatory surgery in the supine position were randomly allocated (according to whether the last digit of the hospital number was odd or even) into two groups for ProSealTM LMA insertion using the digital (even) or SC-guided (odd) techniques. Patients were excluded if they were < 18 yr, < 50 kg, had a known or predicted difficult airway, mouth opening < 2.5 cm, a body mass index > 35 kg·m2, or were at risk of aspiration.

Patients were premedicated with midazolam 0.02 mg·kg–1 iv 15 min before induction. A standard anesthesia protocol was followed and routine monitoring was applied. Anesthesia was in the supine position with the patient’s head on a standard pillow, 7 cm in height. Following preoxygenation for three minutes, anesthesia was induced with a propofol infusion set to a target concentration of 7 µg·mL–1 and remifentanil 0.4 µg·kg–1 iv. The ProSealTM LMA was inserted when there was loss of corneal reflex, apnea and no response to jaw thrust.7 Additional boluses of propofol 0.5 mg·kg–1 iv were given as required until an adequate level of anesthesia was achieved for the ProSealTM LMA placement. The manufacturer’s weight-based recommendations were used for size selection.8 Neuromuscular blocking drugs were not administered. Anesthesia was maintained with a propofol infusion set to a target concentration of 2 to 3 µg·mL–1 and an infusion of remifentanil at 0.05 to 0.2 µg·kg–1·min–1 Face mask ventilation was performed until conditions were suitable for insertion. Patients underwent volume controlled ventilation using O2 33% and air with the tidal volume set at 10 mL·kg–1 and the rate adjusted to maintain the end-tidal CO2 between 35 to 45 mmHg.

The digital technique was performed according to the manufacturer’s instructions8 and involved the use of the index finger to press the ProSealTM LMA into, and advance it around, the palatopharyngeal curve. The SC-guided technique involved the following steps: 1) priming the drain tube with a well-lubricated (KYTM, Johnson and Johnson, Maidenhead, UK) water-based gel 18-FG SC (Vygon Corporation, Norristown, PA, USA) so that it protruded 15 cm beyond the distal aperture of the drain tube (FigureGo); 2) opening the mouth and blindly inserting the SC into the pharynx to a depth of 15 cm at the incisors – slight changes in the trajectory of the SC were permitted, but if persistent tactile resistance was encountered, the SC was placed using a laryngoscope; and 3) digital insertion as above. All insertions were in the sniffing position with the cuff fully deflated and using a midline approach. If tactile resistance was felt at the back of the mouth, a lateral approach was used.9 The lateral approach is identical to the midline approach except that the cuff is not placed symmetrically across the hard palate, but rather placed across it at an angle of approximately 45° with the proximal end pressed against one side and the distal end pressed against the other. The cuff is advanced into the oropharynx with its lateral distal side as the leading edge, and then straightened out once in the laryngopharynx. 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.8 The presence/absence of oropharyngeal air leaks (detected by listening over the mouth),10 gastric air leaks (detected by listening with a stethoscope over the epigastrium),11 drain tube air leaks (detected by placing a lubricant over the proximal end of the drain tube), or an end-tidal CO2 > 45 mmHg was recorded.


Figure 1
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  		FIGURE The ProSealTM laryngeal mask airway drain tube primed with the suction catheter.

 
Three attempts were allowed before insertion was considered a failure. Failed insertion was defined by any of the following criteria: 1) failed passage into the pharynx; 2) malposition (air leaks,11 failed SC insertion if pharyngeal placement successful);12 and 3) ineffective ventilation (no end-tidal CO2 trace, or maximum expired tidal volume < 8 mL·kg–1 or end-tidal CO2 > 45 mmHg if correctly positioned). The time between picking up the prepared ProSealTM LMA (cuff deflated, lubricated, SC attached) and successful placement was recorded. The etiology of failed insertion was documented. If insertion failed after three attempts, an alternative airway management strategy was used. 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 using the manometric stability technique.10

Any episodes of hypoxia (SpO2 < 90%) or other adverse events were documented. All cases were conducted by four experienced users (> 1,000 uses each technique). Any visible or occult blood staining on the ProSealTM LMA or SC was noted at removal. Occult blood was detected by washing each item of equipment in 100 mL water for two minutes and testing it with a dipstick for hemoglobin, as described by Parker and Day.13 The teeth, mouth, lips and tongue were inspected for evidence of trauma.

Patients underwent a structured telephone interview 16 to 24 hr after surgery. Patients 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 were unaware of the insertion technique used. Unblinded trained observers collected the perioperative data, and blinded trained observers collected the data the following day.

Statistics
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 0.915, and was based on studies reporting first attempt success rates.6,14–23 The distribution of data was determined using Kolmogorov-Smirnov analysis.24 Data were compared using a paired t test for parametric data and Chi-squared test for non-parametric data. Data are presented as mean ± standard deviation unless otherwise stated. Significance was taken as P < 0.05. Statistical analysis was performed using SPSS v. 12.0 program (SPSS Inc, Chicago, IL, USA) running on a personal computer.


   Results
TOP
 Abstract
 Introduction
 Methods
 Results
Discussion
 References
 
Demographic data and the mean induction dose of propofol were similar in the two groups (Table IGo). The type/frequency/duration of surgical procedures were similar in the two groups. Insertion success rates, insertion time, etiology of failed insertion, and oropharyngeal leak pressure data are presented in Table IIGo. No patient required laryngoscope guided placement of the SC. Fewer insertion attempts were required with the SC-guided technique (P = 0.02), but first attempt and overall success were similar. The time required to establish an effective airway was shorter for the SC-guided technique (P = 0.02). A lateral approach was required less frequently with the SC-guided technique (P = 0.0004). Mean oropharyngeal leak pressures were similar in the two groups, and there were no adverse events. Airway trauma data are summarized in Table IIIGo. Mouth trauma was more frequent with the digital technique (P = 0.04). There were no differences with respect to the frequency of visible or occult blood, or postoperative airway morbidity (Table IVGo). There were no differences in performance among anesthesiologists.


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  		TABLE I Demographic data and total induction dose of propofol for the suction catheter and digital techniques
 

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  		TABLE II Insertion success, insertion time, etiology of failed insertion and oropharyngeal leak pressure for the suction catheter and digital techniques
 

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  		TABLE III Incidence of airway trauma, and visible and occult blood on the ProSealTM LMA and airway instruments
 

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  		TABLE IV Incidence of airway morbidity at 16 to 24 hr postoperatively
 

   Discussion
TOP
 Abstract
 Introduction
 Methods
 Results
 Discussion
References
 
We found that insertion of the ProSealTM LMA was more successful using the SC-guided technique. Our success rate for the digital technique was similar to previous studies.14,20 The two main causes of failed insertion with the digital technique are impaction with the back of the mouth and glottic inlet.14,17,19,25 The SC-guided technique is more frequently successful because it directs the distal cuff around the oropharyngeal inlet and toward the esophagus; however, impaction can still occur, albeit rarely, as the SC can enter the glottic inlet and the SC may be insufficiently rigid to guide the distal cuff around the oropharynx, where the oropharyngeal axis is < 90°. Insertion can also occasionally fail due to the tongue buckling up at the back of the mouth. One solution to all these problems is to place the SC under direct vision using a laryngoscope, as recommended for the gum elastic bougie-guided technique.15 We used the largest size SC that would fit down the drain tube to increase stiffness. Another useful method for increasing stiffness that we did not evaluate is to cool the SC in a fridge. Magill forceps may occasionally be required to feed the SC into the esophagus. Other potential advantages of the SC-guided technique are (i) the distal cuff is less likely to fold over as the drain tube is stiffer; (ii) the SC is already in the esophagus providing some protection against regurgitation; and (iii) the SC can be used as a guide to reinsertion if the ProSealTM LMA is displaced.

There are three other guides which have been used to facilitate insertion of the ProSealTM LMA. Brimacombe et al. showed that the laryngoscope-guided, gum elastic bougie-guided technique was superior to the digital technique15 and superior to the introducer tool technique if the digital technique failed.26 The advantages over the SC are that the gum elastic bougie is sufficiently rigid to eliminate impaction at the back of the mouth, and can be more easily directed into the esophagus. The disadvantage is that laryngoscope-guidance is required as the bougie is too stiff to be placed blindly. Drolet and Girard4 described the use of a blindly placed gastric tube: the advantage over the SC is that there is no need to insert a gastric tube; and the disadvantage is that it is usually softer, making impaction and misplacement more likely. Brimacombe et al.5 described the use of a fibreoptic scope: the advantage over the SC is that it can easily be directed around the oropharynx and into the esophagus; disadvantages are increased costs and a potential increase in the time required to secure the airway. Perhaps the ideal aid for placement is a guide combining the best features of the SC and gum elastic bougie. Such a guide would have its distal portion like the SC, and the proximal portion resembling the gum elastic bougie.

We found that mouth trauma was more frequent with the digital technique. This is probably related to the increased difficulty with insertion. In principle, it might be related to increased use of the lateral approach, but we consider this unlikely as less resistance is encountered with the lateral approach. There was a trend for increased frequency of airway morbidity with the SC technique (sore throat 11 vs 7%; dysphagia 12 vs 9%; dysphonia 7 vs 3%). A much larger study will be required to confirm or refute this trend. We also found that occult blood was detected on the SC in four of 135 patients. This is higher than reported by Brimacombe et al.15 for the laryngoscope-guided, gum elastic bougie guided technique where no occult blood was detected on the gum elastic bougie in a cohort of 80 patients. We speculate that microscopic mucosal tears occur when the SC rubs against the posterior pharyngeal wall. Perhaps the frequency of occult blood would be reduced if the SC were placed under direct vision.

A limitation of our study is that all insertions were performed by experienced users and our results may not necessarily apply to less experienced personnel. However, we consider that the digital technique probably requires more skill than the SC technique. A further limitation is that the groups were of unequal size. This was due to the technique of randomizing the patients according the whether the hospital number ended in an odd or even digit. This form of randomization is not ideal and may have led to differences between group characteristics. Finally, intraoperative data were collected by unblinded observers – a possible source of bias.

We conclude that the SC technique is more frequently successful than the digital technique and is associated with less mouth trauma during insertion of the ProSealTM LMA.


   Footnotes
 
Accepted for publication May 1, 2005. Revision accepted November 1, 2005.

Competing interests: Dr. Brimacombe has previously worked as a consultant for the Laryngeal Mask Company and Mallincrodt Medical.

This study was supported solely by departmental funds.


   References
TOP
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
1 Brain AIJ, 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 Brimacombe J. ProSeal LMA for ventilation and airway protection. In: Laryngeal Mask Anesthesia. Principles and Practice. London: WB Saunders; 2005, 505–38.

3 Garcia-Aguado R, Vivo M, Dura R, et al. New method for inserting the Proseal laryngeal mask using an aspiration catheter in a case of difficult airway. Rev Esp Anestesiol Reanim 2004; 51: 58–9.[Medline]

4 Drolet P, Girard M. An aid to correct positioning of the ProSeal laryngeal mask. Can J Anesth 2001; 48: 718–9.[Free Full Text]

5 Brimacombe J, Keller C. Awake fibreoptic-guided insertion of the ProSeal laryngeal mask airway. Anaesthesia 2002; 57: 719.[Medline]

6 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.[Medline]

7 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.[Medline]

8 LMA ProSealTM Instruction Manual, 1st ed. San Diego: LMA North America Inc; 2000.

9 Brimacombe J. Placement phase. In: Laryngeal Mask Anesthesia. Principles and Practice. London: WB Saunders; 2005, 265–80.

10 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.[Abstract/Free Full Text]

11 Brimacombe J, Keller C, Kurian S, Myles J. Reliability of epigastric auscultation to detect gastric insufflation. Br J Anaesth 2002; 88: 127–9.[Abstract/Free Full Text]

12 Brimacombe J, Keller C, Berry A, Mitchell S. Assessing ProSeal laryngeal mask positioning: the suprasternal notch test (reply). Anesth Analg 2002; 94: 1375.[Free Full Text]

13 Parker MR, Day CJ. Visible and occult blood contamination of laryngeal mask airways and tracheal tubes used in adult anaesthesia. Anaesthesia 2000; 55: 388–90.[Medline]

14 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]

15 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.[Medline]

16 Brimacombe J, Keller C, Brimacombe L. A comparison of the laryngeal mask airway ProSealTM and the laryngeal tube airway in paralyzed anesthetized adult patients undergoing pressure-controlled ventilation. Anesth Analg 2002; 95: 770–6.[Abstract/Free Full Text]

17 Evans NR, Gardner SV, James MF, et al. The ProSeal laryngeal mask: results of a descriptive trial with experience of 300 cases. Br J Anaesth 2002; 88: 534–9.[Abstract/Free Full Text]

18 Brimacombe J, Keller C. Stability of the ProSeal and standard laryngeal mask airway in different head and neck positions. A randomised crossover study. Eur J Anaesthesiol 2003; 20: 65–9.[Medline]

19 Keller C, Brimacombe J. Mucosal pressure and oropharyngeal leak pressure with the Proseal versus the classic laryngeal mask airway. Br J Anaesth 2000; 85: 262–6.[Abstract/Free Full Text]

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

21 Lu PP, Brimacombe J, Yang C, et al. The ProSeal versus the classic laryngeal mask airway for positive pressure ventilation during laparoscopic cholecystectomy. Br J Anaesth 2002; 88: 824–5.[Abstract/Free Full Text]

22 Keller C, Brimacombe J, Kleinsasser A, Brimacombe L. The laryngeal mask airway ProSealTM as a temporary ventilatory device in grossly and morbidly obese patients before laryngoscope-guided tracheal intubation. Anesth Analg 2002; 94: 737–40.[Abstract/Free Full Text]

23 Brimacombe J, Keller C, Boehler M, Puehringer F. Positive pressure ventilation with the ProSeal versus classic laryngeal mask airway: a randomized, crossover study of healthy female patients. Anesth Analg 2001; 93: 1351–3.[Abstract/Free Full Text]

24 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.[Medline]

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

26 Brimacombe J, Keller C. Gum elastic bougie-guided insertion of the ProSealTM laryngeal mask airway. Anaesth Intensive Care 2004; 32: 681–4.[Medline]




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This Article
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