Year : 2009 | Volume
: 53 | Issue : 4 | Page : 414--424
Troubleshooting ProSeal LMA
Bimla Sharma1, Jayashree Sood2, Chand Sahai1, VP Kumra3,
1 Senior Consultant, Department of Anaesthesiology, Pain and PerioperativeMedicine, Sir Ganga RamHospital,Old Rajinder Nagar,New Delhi-110 060, India
2 Senior Consultant, Chairperson, Department of Anaesthesiology, Pain and PerioperativeMedicine, Sir Ganga RamHospital,Old Rajinder Nagar,New Delhi-110 060, India
3 Emeritus Consultant, Department of Anaesthesiology, Pain and PerioperativeMedicine, Sir Ganga RamHospital,Old Rajinder Nagar,New Delhi-110 060, India
Department of Anaesthesiology, Pain and PerioperativeMedicine, Sir Ganga RamHospital, Old Rajinder Nagar, New Delhi-110060
Supraglottic devices have changed the face of the airway management. These devices have contributed in a big way in airway management especially, in the difficult airway scenario significantly decreasing the pharyngolaryngeal morbidity. There is a plethora of these devices, which has been well matched by their wider acceptance in clinical practice. ProSeal laryngeal mask airway (PLMA) is one such frequently used device employed for spontaneous as well as controlled ventilation. However, the use of PLMAat tunes maybe associated with certain problems. Some of the problems related with its use are unique while others are akin to the classic laryngeal mask airway (eLMA). However, expertise is needed for its safe and judicious use, correct placement, recognition and management of its various malpositions and complications. The present article describes the tests employed for proper confirmation of placementto assess the ventilatooy and the drain tube functions of the mask, diagnosis of various malpositions and the management of these aspects. All these areas have been highlighted under the heading of troubleshooting PLMA. Many problems can be solved by proper patient and procedure selection, maintaining adequate depth of anaesthesia, diagnosis and management of malpositions. Proper fixation of the device and monitoring cuff pressure intraoperatively may bring down the incidence of airway morbidity.
|How to cite this article:|
Sharma B, Sood J, Sahai C, Kumra V P. Troubleshooting ProSeal LMA.Indian J Anaesth 2009;53:414-424
|How to cite this URL:|
Sharma B, Sood J, Sahai C, Kumra V P. Troubleshooting ProSeal LMA. Indian J Anaesth [serial online] 2009 [cited 2021 Jan 27 ];53:414-424
Available from: https://www.ijaweb.org/text.asp?2009/53/4/414/60312
The ProSeal latyngealmask airway (PLMA) is the most complex and advanced version among all the laryngeal mask airways (LMAs). , Some of the problems with its use are unique, such as oesophageal aspiration of air, gastric distension and airway obstruction which can occur even when the PLMA is correctly placed with a proper insertion technique ,, .The other problems encountered are akin to the classic laryngeal mask airway (cLMA), with varying degrees of frequency and intensity. As a routine after insertion and inflation of the PLMA cuffto 60 cm H2O, the correct placement of the device is confirmed by several observations and certain specific tests designated to assess PLMA positioning and evaluate the ventilatooy and drain tube functions of the mask. These diagnostic tests are simple and quickto perform and the first five of the following are more popular.
Visual assessment of depth of insertionUnobstructed inspiratory and expiratoty flow Suprastemal notch tap test Gel displacementtestPassage of gastric tube/ polyvinyl chloride (PVC) catheter through drain tubeSoap bubble test Thread testSelf-inflating bulb techniqueTrachlight TM testMaximum minute ventilation (MMV) test
After confirming correct positioning, the PLMA is properly secured to avoid dislodgement as its cuff is bulkier than that of the cLMA.
1. Visual assessment of depth of insertion
Assess for adequate depth of insertion by examining the relation of the integral biteb lockto the incisors. Ideally the biteb lock lies between the teeth but protrudes in casethePLMA is inadequately inserted. Stix and 0' Connorin a study of 274 achults, found that when the PmS & LMA was correctly positioned, the midway point of the bite block was proximal to the incisors in 78% ofwomen and 92% ofmen.APLMA with its bite block lying entirely outside the mouth is almost unquestionably malpositioned 
2. Unobstructed insp iratory and expiratory flow
This is assessed by manually ventilating the patient, observing chest movements,capnography, expired tidal volume (V T ) of > 8m11kg, and evaluating the compliance by feel of the bag The reported incidence ofairway obstmction with PLMA has been found to vary from 2-10%. , . Increased resistance is suspected with partial obstruction resulting from infolding of the PLMA aifl or downfolding of epiglottis.  ThePLMA, with its large drain tube and cull,, may produce respiratory obstuction by displacing the crieoid cartilage anteriorly the - eby exerting directpressure on the arytenoid bodies and muscular processes. 
3. Sup rastemal notch tap test or Brimacombe bounce
The suprasternal notch tap test or the "Brimacombe bounce" confirms the location of the PLMA tip in the oesophagus behind the crieoid cartilage. The test was first described by 0' Connoretal in 2002.  It involve stapping the suprasternalnotch or crieoid cartilage, and observing simultaneous movement of a column of lubricant, cra soap bubble mentrane at the proximalend of the draintube Both the structures lie in close proximity to the hypopharynx, where the correctly placed distal cuff sits The drain tube must b e patent for the test to be positive The test works by cuff compressiar causing drain tube compression within the draintube,which intum moves the habricantorscep bubble. 0' Connoretal  rep orted a low false-negativerate for the suprastenal notch tap test in 50 adults, butfalse positives and negatives can occur. False pesitives can occur if the last 1-2 cm of the drain tube is folded over but some of the drain tube is still p atent within the distal cuff  .False negatives can occur if the oesophagus is open, since this can weaken the pressure wave.
4. Gel Displacement Test
Water-soluble gel (0.5-1 ml) isp laced at the proximal end of the drain tube so that it forms a column of about 2-3 cm. Minimal movement or gentle up and down movements indicates anormalposition. However, gelej action with gentle positivepressure ventilation (PPV), indicates a leak from the draintube, signifying improper seal of device with the hypopharynx [Figure 1]. Thus, when p ositive, the test indicates airway leak thourgh the drain tube , .
5. Passage of gastric tube! PVC catheterthrough drain tube toverify the patency of drain tube
The posterior folding of the mask tip is ruled out by the successful passage of a gastrictube or a PVC catheter through the drain tube ,, .
6. Soap Bubble Test
In this test, soap bubble solution is placed over the tip of the drain babe and following observations may be made. When the tip of the PLMA is in the laryngopharynx, soap bubble solution column bubbles or the soap membrane bursts during positive pressure ventilation. When the PLMA tip enters the glottis, the tracheobronchial tree communicates directly to the drain tube. The drain tube transmits the airway pressures unless it is obstructed. The PLMA insertion into the glottis is diagnosed by watching either the fonnation of a spontaneous bubble which is blown away from drain tube port orthe soap membrane oscillations seen with cardiac rhythm of the patient. , .
7. Thread test
A gauze thread or small piece of cotton held over the proximal end of a leaking drain tube can also be used to detect air leak from the drain tube. 
8. Self-inflating bulb technique
This technique has been used forverification of proper placement of the oesophageal tracheal combitube®.  Aself-inflating bagis attached to the drain tube, the bulb injects easily and then remains collapsed with normal positioning of the PLMA. However; during glottis insertion, the self-inflating bulb injects easily and then re-inflates. 
9. Trachlight TM
The Trachlight TM helps in quickly distinguishing glottis from oesophageal location of the tip of the PLMA mask. Trachlight TM (Laerdal Medical, Wappingers Falls, NY, USA) after removing its stylet is passed through the drain tube just as for blind endotracheal intubation.  This is a simple and reliable means of detecting a PLMA tip fold over.  Adull glow in the anterior neck with passage of the Trachligh TM wand beyond the drain tube tip indicates correct alignment of the PLMAwith the upper esophageal sphincter.
10. Maximum Minute Volume Ventilation (MMV)
The MMV test consists of manually hyperventilating an anaesthetized and paralyzed patient with a PLMA for 15 seconds and extrapolating the total exhaled volume to one minute which can be graded as follows.
Basal value 5-7 L/min
Critical value 6-12L/min, threshold for removal of PLMA
Mean value 26-29 L/min
The testis easy to perform and can be completed with equipment that is readily accessible to almost every anaesthesiologist.
Anaesthesiologists should be alerted to the potential for significant airway obstruction in any patient with a MMV less than 12 Llmin. It is advisable toremove the PLMA and use an alternative device before the initiation of surgery.  In this scenario, one should not have a false sense of security due to the normal oxygen saturation as the latter does not guarantee the satisfactory elimination of CO 2 .  However, the decision to remove the PLMAshould be based depending on the patient's physical status, nature, site and duration of surgery.
Problems related to the PLMA might occur during: i) insertion of the device ii)maintenance/ emergence phases of anaesthesia iii) recovery phase; in the post anaesthesia care unit or in the ward. Most of the problems are detected in the perioperative period but some airway morbidity and nerve injuries might continue even afterthe patient has been discharged from the hospital Various tools required forthe purpose of trouble shooting are the PLMA its elf with its cuff, drain tube and bite block, pressure gauge to monitor the oropharyngeal seal pressure, cuff pressure monitor, cotton, gauze thread, water soluble gel, and soap solution. Availability ofrespiratory module and fiberoptic scope can be very helpful in diagnosis and management of various malpositions. Common problems associated with
I. Functional failure
This may result from several factors. The etiology could vary from failure to negotiate the cuffthrough the oral cavity, various malpositions to mechanical and dynamic causes contributing to airway obstruction inspite of a correctly placed device. 
A. Device Insertion failure
The first-tine and overall insertion failure rate is 14% and 1% respectively.  This phase may be associated with problems such as difficulty in insertion due to the following reasons
(i) Disproportionate oral aperture
Small oral aperture, inability to open mouth fully such as TM joint ankylosis, inappropriate size of the mask and mask not properly deflated before attempting insertion
(ii) Small oral cavity, small pharynx
(iii) Resistance encountered at posteriorpharyngeal wall during insertion
(iv) Short neck
(v) Light plane of anaesthesia such as coughing, gagging, retching, stridor, hiccup, or biting of device.
Inability to negotiate the mask through oral aperture
Corrective measures ,, , , ,
Proper selection of maskLateral approach where the cuff enters the oropharynx from the side of the hard palate.Openingthe patient's mouth with a laryngoscope followed by insertion of the deviceGum elastic bougie /frberoptic insertion, PVC / gastric tube as stents to stiffen the drain tube  Deepening level of anaesthesiaJaw thrust
B. Gastric tube insertion failure and gastric insufflation
The failure rate for gastric tube insertion is 4%. The most common causes of failure of gastric tube placement are: 
Inadequate lubricationSelection of unproper sizePosteriorfolding of the mask Cooled gastric tube
The failure rate for prevention of gastric insufflation during PPV is 0.1% which is similar to the incidence seen with thetrachealtube. 
C. Dislodgement with loss of airway during maintenance phase
'Ihe PLMA gets dislodged resulting in loss of airway duringthe maintenance phase dueto lightplane of anaesthesia, improper fixation and changes in position e.g. extreme head down position during gynaecologic surgery and laparoscopic procedures. This can be avoided by proper fixation of the device. In the event of intraoperative displacement of the device, a gastric tube left in situ may be very helpful reinsertion of the device by simply railroadingthe drain tube over the gastric tube. 
One of the many advantages of PLMA over other LMAfamilymembers isthat its malposition can be diagnosed and managed. , Slight malrotation is more common with the PLMA as compared to the cLMA probably because of residual rotation in the sagittalplane or distortion of glottic geometry.  Severalmalpositions havebeen described and the reported incidence is 515% at the first attempt. [19,, The instruction manual describes three malpositions; [l], (i) insufficient insertion depth, (ii) PLMA insertion into the glottis, (iii) PLMA tip folded backwards behind the bowl against the posterior pharyngealwall.
Presently six malpositions (with approximate incidence) have been described. ,,
Distal cuffin laryngopharynx (7%)  Distal cuff in glottic inlet (3-6%) , Distalcufffolded over (3.4%)  Severe epiglottis downfolding(  Supraglottic and glottis compression (0.4%)  Infolding of cuff (0.6%) 
1. Distal cuff in laryngopharynx
When the PLMA is not inserted to the desired depth, the distalcuff sits in the laryngopharaynx resulting in protrusion of the bite block. ,,,
Bite block protrudingSoap bubbletest positive
Further pushing in of the PLMA without colliding with the glottis inlet .,
2. Distal cuff in glotticinlet/PLMAinsertion into the glottis
When the PLMA takes an anterior path during insertion, the distal cuff collides with the glottis inlet and either remains there or falls back in the laryngopharynx. PLMA entry into the glottis is notuncommonduringinsertion attempts because of the bulky and flexible mask tip. When the PLMA enters the glottis then the drain tube acts as an extension of the tracheobronchial tree, airway pressures are therefore transmittedthrough the drain tube and notthe airwaytube. ,
Thread testGel displacementSoap bubble testSelf-inflating bulb technique Trachlight™
Correction usually requires reins ertion using a latreal approach, of the gum elastic bougie (GEB) technique. In majority of cases, the reinsertion of the mask is to a noticeably increaseddepth of insertion. Location of the PLMA tip in the oesophagus behind the cricoid cartilage can be confined using the "suprasternalnotch tap test."  To distinguish between inadequate depth of insertion and glottis imp action, the PLMA can be pushed further inwards: the former will usually be corrected while the latter made worse, with increased airway obstruction or airway protective reflex activation.  O'Connor and Stix have suggested that these malpositions can be distinguished using the soap bubble test. ,
3. Distal cuff folded over
The advancing distal cuff of the PLMA gets folded [Figure 2] when it impacts against the posterior oropharyngealwall thereby obliterating the lumen of the drain tube. , Thus the distal cuff folds up beneath the advancing cuffuntilthe unfolded proximal cuff is redirected inferiorly into the laryngopharynx by the build up of the folded cuff in the oropharynx. The folded distal cuff cannot easily unfold as it gets wedged into the laryngopharynx. Folding over has also been reported with the cLMA,  but is probably more common with the PLMA due to its soft backplate.  This malposition may occur with both finger / introducerinsertion and be associated with a better seal and highermucosal pressures than the correctly placed PLMA.
Brimacombe et al, in a study of 95 patients with the fold over malpositions, found that in 92% resistance was encountered at the back of the mouth, in 83% the bite blockpmtruded from the mouth, and in 98% ventilation was unaffected and the sealwas normal.  The main danger of unrecognised fold over phenomenon is that it predisposes the patient to gastric insufflation, regurgitation and pulmonary aspiration as ventilation is unhindered due to easily achieved high airway pressures.  Thepatency of the draintube must be assessed in allpatients with the PLMA to exclude this malposition. In situations where passage of a gastric tube is not required, the patency can be tested by non-invasively passing the gastric tube or a PVC suction catheter only till the end of the drain tube.
Resistance encountered at the back of the mouthBite block lying outsideInability to pass a gastric tube/PVC catheterth mugh the drain tubeUnaffected ventilation and sealpressure
Corrective measures ,,
Reinsertion using a lateral approachReinsertion with the drain tube stiffened using a stylet Guided insertion with a gum elastic bougie (GEB) Digital correction by sweepinga fingerbehind the cuff
Of these, digital correction app ears to be the least effective. Folding over cannot occur with the GEB insertion and gastric tube guided techniques.
4. Severe epiglottic downfolding
A well known cause of mechanical airway obstruction is severe epiglottis downfolding which occurs when the epiglottis is dragged inferiorly by the cuff and completely covers the laryngeal inlet [Figure 3]. Itis diagnosed when the anterior surface of the epiglottis is visible from the airway tube on fiberscope examination. 
Although a degree of downfolding of epiglottis has been reported in 17% of cases,  critical airway obstruction seldom occurs from a downfolded epiglottis due to the design feature as the drain tube always suspends the epiglottis offthe floor of the bowl. However, with cuff infolding (thetwo outside cuffs meet in the midline and the epiglottis cannot enter the bowl), a downfolded epiglottis becomes a riskfactor for airway obstruction because itis nowforced directly onthe arytenoids.  It may occur as aresult ofpre-insertion inflation of cuff, compression of pharynx and enlarged or floppy epiglottis.
High airway pressures Airway obstruction MMV test Fiberopatic examination
Corrective measures ,,
Reinsertion with the head/neckin a more extreme sniffing positionJaw thrust Laryngoscope guided placement of PLMA
5. Sup raglottic and Glottis Compression
Glottis compression occurs when the glottis inlet is mechanically compressed by the distal cuff reducing the tension of the vocal cords.  It is more likely to occur with a small pharynx, over inflated cuff and when the distal cuff is pressed into the hypophatynx with extra force.  Compression of supraglottic and glottic structures may occasionally contribute to significant upper airway obstruction with a correctly placed tip of the cuff lying behind the cricoid cartilage. 
High airway pressures Airway obstruction MMV test
Corrective measures ,,
Reinsertion does not usually solve the problem.
Air should be withdrawn from the cuff Anteroposterior diameter of the pharynx increased by adopting the sniffing position
6. Cuff infolding
Cuffinfolding refers to inward rotation of the large cuffs in front of the bowl so that they contact each other in the midline and obstruct gas flow [Figure 4]. Itis relatively uncommon and Stix reported 2 cases of cuff infolding out of 317 cases. , It is clinically indistinguishable from severe downfolding of epiglottis and both conditions may coexist at times. There is increased risk of cuff infolding with PLMA due to its deeper bowl and a more compliant cuff than that of the cLMA.Z 
High airway pressures Airway obstruction MMV testFiberoptic examination
Corrective measures ,
Sniffing position which increases the anteroposterior diameter of the pharynxApplying jawthrustConsider insertion of one size smaller LMA-ProSeal TM Ensure correct cuff inflation pressuresAir withdrawal from the cuff may be helpful
[Table 1] shows Troubleshooting to various problems, causes, the required confirmatory test and their solutions.
II. Regurgitation and aspiration Regurgitation of gastric contents may result in Supracuff soiling of the mask and pulmonary aspiration with catastrophic results. , This may be precipitated by activation of protective reflexes due to lightplane of anaesthesia as greater depth of anaesthesia is required for insertion of PLMA as compared to cLMA. 
Fluid seen in the airway /drain tubeIntraoral examinationFiberoptic examination of the tracheobronchial tree Sudden bronchospasm Haemodynamic instability Supracuff soiling of the maskon removal
Management of Regurgitation[ 31]
Leave the PLMAin situSuction of the gastric tube and the drain tubeHead clown position and 100% oxygen should be administeredFib eroptic evaluation and suction Consider deepening level of anaesthesia and intubation of the patient fiberoptically via the PLMA
III. Airway morbidity and Trauma
Airway morbidity and trauma may result from difficulty and multiple attempts at insertion, prolonged surgery without intracuffmonitoring and unpropersize selection of the PLMA. 
Coughing, gagging, retching stridor, hiccup, orbitingAudible noise, or as subtle increases in airway pressure orreductions in tidal volume Laryngospasm, bronchospasm, regurgitation, and aspiration
Eliminating the source of stimulation Deepening anaesthesiaHead down position and 100% oxygen should be administeredBronchodilators or high concentration of volatileagent
Many problems can be solved by proper patient and procedure selection, diagnosis and management of malpositions. Strategies to facilitate insertion by lateral/guided ins ertion techniques and maintaining adequate plane ofanaesthesia may be helpful in improving first time and overall insertion success rates, correcting malpositions, overcoming difficult airway scenarios and prevention of regurgitation and pulmonary aspiration. Proper fixation of the device and monitoring cuff pressure intraop eratively especially during nitrous oxide based anaesthesia may bring down the incidence of airway morbidity.
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