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CLINICAL INVESTIGATION
Year : 2008  |  Volume : 52  |  Issue : 3  |  Page : 288-296 Table of Contents     

Efficacy and Safety Performance of ProsealTM Laryngeal Mask Airway in Laparoscopic Surgery: Experience of 1000 Cases


1 Senior Consultant, Department of Anaesthesiology, Pain and Perioperative Medicine, Sir Ganga Ram, Hospital, Old Rajinder Nagar, New Delhi-110060, India
2 Senior Consultant and Chairperson, Department of Anaesthesiology, Pain and Perioperative Medicine, Sir Ganga Ram, Hospital, Old Rajinder Nagar, New Delhi-110060, India
3 Emeritus Consultant, Department of Anaesthesiology, Pain and Perioperative Medicine, Sir Ganga Ram, Hospital, Old Rajinder Nagar, New Delhi-110060, India

Date of Acceptance07-Apr-2008
Date of Web Publication19-Mar-2010

Correspondence Address:
Bimla Sharma
Department of Anaesthesiology, Pain and Perioperative Medicine, Sir Ganga Ram Hospital, Old Rajinder Nagar, New Delhi-110060
India
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Source of Support: None, Conflict of Interest: None


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The ProSeal TM laryngeal mask airway (PLMA) has been especially designed for positive pressure ventilation and protection against aspiration. We tested the efficacy and safety of the PLMA as a ventilatory device for a variety of commonly performed laparoscopic surgeries. The PLMA was used for the airway management of one thousand; consecutive anaesthetized, paralysed patients, aged 13-86 years belonging to ASA physical status I-III scheduled for elective laparoscopic and extraperitoneal endoscopic surgeries. Details of insertion, oropharyngeal seal pressure (OSP), ventilatory performance and safety data of the PLMA were recorded. During surgery, oxygenation and ventilation variables were adjusted to maintain SpO2 > 95 %, as measured by pulse oximetry and EtCO2 < 46 mm Hg, respectively. The success rate of PLMA insertion and gastric tube placement was 100 %. One patient had short lived SpO2 of 94 % while three patients showed transient increase in EtCO2 > 55 mm Hg. Twenty five (2.5%) patients showed gastric regurgitation, suctioned through the oesophageal channel of the PLMA, but no case of pulmonary aspiration was detected. Median OSP was 36 cm H2O. The median peak inspiratory pressure (PIP) before and after CO2- insufflation were 10 and 18 cm H2O, respectively (P < 0.001). Our study demonstrated that the PLMA, in experienced hands, is an efficient and safe airway tool for the airway management of patients undergoing elective laparoscopic surgery.

Keywords: Equipment; ProSeal laryngeal mask airway; Intubation; Tracheal; Surgery; laparoscopy.


How to cite this article:
Sharma B, Sood J, Sahai C, Kumra VP. Efficacy and Safety Performance of ProsealTM Laryngeal Mask Airway in Laparoscopic Surgery: Experience of 1000 Cases. Indian J Anaesth 2008;52:288-96

How to cite this URL:
Sharma B, Sood J, Sahai C, Kumra VP. Efficacy and Safety Performance of ProsealTM Laryngeal Mask Airway in Laparoscopic Surgery: Experience of 1000 Cases. Indian J Anaesth [serial online] 2008 [cited 2019 May 24];52:288-96. Available from: http://www.ijaweb.org/text.asp?2008/52/3/288/60636


   Introduction Top


The ProSeal™ laryngeal mask airway (PLMA) is a directional perilaryngeal sealer owing to its unique cuff and double tube design that allows an oropharyn­geal seal of > 30 cm H 2O without an increase in the directly measured mucosal pressure when compared to the classic laryngeal mask airway (cLMA). [1],[2],[3] It en­ables positive pressure ventilation (PPV) at higher peak inspiratory pressure (PIP). When properly placed, its drain tube separates the alimentary and respiratory tracts, detects malposition and provides protection against aspiration in fasted patients as supported by design, clinical, laboratory, and cadaveric evidence. [1],[2],[3],[4],[5],[6] These features, together with the flexible, non-kinkable airway tube increase its safety profile. Although the tra­cheal tube is considered ideal for laparoscopic proce­dures, there is a consistent inflow of reports highlight­ing the safety of PLMA in laparoscopic surgery. [7],[8],[9],[10],[11],[12],[13],[14] In this prospective study, we evaluated PLMA as an air­way management device for a wide variety of com­monly performed laparoscopic surgeries. The primary outcome of the study was defined as the efficacy and safety of the device and the secondary outcome to assess the pharyngolaryngeal morbidity.


   Methods Top


Following institutional ethics committee approval and written informed consent, this prospective study comprising one thousand consecutive patients, aged 13-86 years, ASA physical status I-III, scheduled for elective laparoscopic surgery was undertaken. Patients with mouth opening less than 2.0 cm, abnormality of neck, upper respiratory and alimentary tract, a body mass index in excess of 40 kg m -2 , previous gastric surgery, hiatus hernia, acute abdomen, poorly controlled diabetes mellitus and those with a risk of pulmonary aspiration were excluded from study. The device was inserted by anaesthesiologists experienced with LMA use (cLMA > 100, PLMA > 50 insertions). The fol­lowing parameters were studied: i) Ease of insertion and number of attempts, ii) Oropharyngeal seal pres­sure (OSP) iii) Ventilation: PIP, SpO 2 and EtCO 2, iv) Safety: device displacement, oropharyngeal leak, gas­tric insufflation, regurgitation and aspiration, and v) Pharyngolaryngeal morbidity. The change in PIP be­fore and after carbon dioxide insufflation was taken as the primary variable. Wherever possible, fibreoptic evaluation of the device placement was done via air­way and drain tubes.

Anaesthesia protocol

A standard general anaesthesia protocol was followed and routine monitoring was applied in all pa­tients. Oral alprazolam 0.25 - 0.5 mg, was given the night before surgery; intravenous midazolam 1-2 mg, ranitidine 50 mg, metoclopramide 10 mg 2 h preop­eratively, and glycopyrrolate 0.2 mg intravenously 30­45 min before surgery. Anaesthesia was induced with fentanyl 1mcg kg -1 and propofol 2 mg kg -1 and main­tained with propofol infusion 2 mg kg -1 hr -1 , sevoflurane 1% and nitrous oxide 66% in oxygen. Neuromuscular blockade was achieved with vecuronium bromide 0.08 mg kg -1 and maintained with 0.02 mg kg -1 boluses. PLMA was inserted after the jaw was relaxed. Tra­cheal intubation was considered after three failed PLMA insertion attempts. The patient's lungs were ventilated via a circle-CO 2 - absorber breathing system (Penlon Prima SP, AV 900 ventilator, Abingdon, UK). Dura­tion of CO 2 insufflation and anaesthesia were noted in all cases. At the end of surgery, the neuromuscular blockade was reversed with neostigmine 0.05 mg kg -1 and atropine 0.02 mg kg -1 . The patient's mouth was carefully inspected for damage to the tongue, lips and teeth after removing the PLMA.

Airway management and ventilation strategy

Appropriately sized PLMA (# 3 / # 4) in females and (# 4 / # 5) in males and obese females were cho­sen. The cuff was fully deflated and the posterior as­pect lubricated with a clear water based gel (KY jelly, Johnson& Johnson, U.S.A). With the patient's head on a firm 7- cm high pillow, the PLMA was inserted in the pharynx using the index finger or the introducer tool. Where difficult insertion of the PLMA was an­ticipated, the placement was aided by one of the fol­lowing techniques: laryngoscope-aided placement, laryngoscope-guided gum elastic bougie/ polyvinylchloride catheter / gastric tube guided inser­tion technique. Correct placement of the device was confirmed by manual ventilation, expired tidal volume (V T ) of > 8 ml kg -1 , square wave capnography and the gel displacement test. [2] Posterior folding of the mask was ruled out by inserting either a gastric tube or a PVC suction catheter through the drain tube. The cuff was inflated to a pressure of 60 cm H 2 O using a cuff pressure monitor (Mallinckrodt Medical, Athlone, Ire­land). Number of attempts for gastric tube placement was recorded and its correct placement confirmed. Gas­tric contents were suctioned and measured for volume and pH. The time interval between holding the PLMA to confirmation of correct placement by bilateral air entry on chest auscultation was noted. The device was se­cured as per manufacturer's recommendation.

Mechanical ventilation was initiated with FiO 2 0.3, V T - 8-10 ml kg -1 , I/E ratio of 1:2 and respiratory rate of 12 per minute. The FiO 2 and respiratory rate were adjusted to maintain SpO 2 > 95 % and EtCO 2 be­tween 35 - 45 mm Hg. The preset insufflation pressure was kept between 12-14 mm Hg for all procedures except in ASA III patients where it was kept between 10-12 mm Hg. The surgeon graded the gastric insuf­flation on a 4 point score: 0= no gastric insufflation, 1= minimal gastric insufflation, not interfering with surgery, 2= interfering with surgery, but not necessitating change of device, 3= interfering with surgery, and necessitating change of device. Presence of any audible leak during the procedure was recorded.

PLMA ventilatory performance and fibreoptic position

Oropharyngeal seal pressure was determined at fixed gas flow of 5 litre min -1 by closing the expiratory valve of the CO 2 -circle system and recording the air­way pressure at which equilibrium was reached (maxi­mum 40 cm H 2 O). [2] Suboptimal oxygenation was de­fined as SpO 2 between 90-95 % and hypoxia as SpO2 < 90 %. PIP and EtCO 2 were noted i) after securing airway (baseline), ii) after CO 2 insufflation, iii) intraop­eratively every five minutes, iv) after any change of po­sition and upon v) desufflation. Ventilation was consid­ered unsuitable if EtCO 2 exceeded 46 mm Hg and hypoventilation was defined by EtCO 2 > 55 mm Hg. Flexible fibreoptic scope (Olympus LF-2) view of the laryngeal structures was graded on the following scor­ing system; 4= vocal cords only; 3= vocal cords plus posterior epiglottis (PE); 2= vocal cords plus anterior epiglottis (AE); 1= vocal cords not seen. [15] The view from the drain tube was catalogued as: hypopharynx (mucosal); oesophageal sphincter open (clear view down the oesophagus); and others (glottis, epiglottis,arytenoids). [16]

Safety data

The following intraoperative events and compli­cations were documented: PLMA displacement, oropharyngeal leak, gastric insufflation, oesophageal re­gurgitation, pulmonary aspiration, bronchospasm, air­way obstruction, tongue-lip-dental trauma. The PLMA was removed after completion of procedure, when the patient was wide-awake. Any blood detected on the device on removal was recorded. Secretions over ven­tral and dorsal aspect of the PLMA were tested for pH with a litmus paper sensitive to changes of 0.5 unit pH from pH 2.5 to 8.5.

Postoperatively, the patients were monitored in the post anaesthesia care unit by an observer, blinded to the technique, for a minimum of 2 hours. Heart rate, arterial pressure, SpO2, respiratory rate, and any inci­dence of nausea and vomiting were recorded. They were actively questioned about the presence of sore throat, dysphagia and dysarthria in the post anaesthe­sia care unit and over ensuing 24 hours.

Statistical analysis

Statistical tests were performed using SPSS soft­ware, (10.0 version; SPSS Inc., Chicago, IL, USA) and results are reported as absolute, percentage, range or median (interquartile range). The Kolmogorov­Smirnov test indicated that data were not normally dis­tributed, hence non-parametric tests; Chi-square, Fisher's exact, Mann-Whitney U and Wilcoxan Sig­moid Rank tests were applied as appropriate. Signifi­cance was taken as P < 0.05. We considered a 25% rise in PIP after CO 2 insufflation to be clinically signifi­cant. The sample size allowed a projected difference of 25% to be detected for the primary variables for a type I error of 0.05 and a power of 1. Other variables tested were PLMA TM device insertion success rates and times, efficacy of seal, fibreoptically anatomic position, orogastric tube insertion success rates and total intra­operative respiratory complications. The variable re­quiring the largest sample size was aspiration and keep­ing in mind the low incidence of aspiration with the PLMA in elective surgery, our study of 1000 patient is not sufficiently powered.


   Results Top


The surgical procedures, patient characteristics and details of anaesthesia and airway management are shown in [Table 1]& [Table 2].

PLMA insertion, gastric tube placement success rate and fibreoptic examination.

The PLMA and gastric tube could be placed in all 1000 patients. Size 3 PLMA was used in 256 fe­male patients and size 4 in 239 male patients. First time insertion success rate of PLMA was 86.6% and there was no case of failed insertion. Gastric tube was left in situ in 814 patients, successfully placed on first attempt in all the patients. Fibreoptic examination was conducted in 157 cases [Table 3].

Ventilatory and oxygenation efficacy

[Table 4] shows the oxygenation, ventilation profile and the peri-insufflation data.

Optimal oxygenation was noted in all cases be­fore CO 2 - insufflation. No patient experienced SpO 2 less than 94 % after CO 2 insufflation. Three patients had EtCO 2 in excess of 55 mm Hg after CO 2 - insuffla­tion. The median OSP was 36 (6) cm H 2 O [Table 2] and over a quarter of our patients recorded an upward trend which would have resulted in OSP exceeding 40 cm H 2 O. There was a significant increase in the PIP after CO 2 - insufflation (P < 0.001).

Safety data

There was no incidence of intraoperative displace­ment of the device. Gastric insufflation grade 1 and 2 was noted in two and five patients respectively. There was no case of regurgitation into the bowl of the mask. Gastric contents were suctioned through the oesoph­ageal channel of PLMA in twenty-five (2.5%) patients. Fluid [4.75 ± 9.19 ml (range 0 to 75 ml), pH range 2.5 to 6.5] was aspirated from the gastric tube in 136 (25%) out of 814 patients. No patient had pH less than 6.0 on dorsal and ventral PLMA cuff. No case of pulmonary aspiration was detected.

Postoperative pharyngolaryngeal morbidity

Most complications were minor in nature [Table 5]. Excessive secretions were noted in six patients and blood staining of the mask upon removal was found in 29 patients which increased with number of attempts at insertion (P < 0.05) and was higher in female pa­tients (P < 0.05). Minor lip and dental trauma was no­ticed in fifteen patients. Sore throat, dysphagia, and dysarthria were reported in twenty-five, two and one patient, respectively. Only one patient had vomiting in the post anaesthesia care unit.


   Discussion Top


A total of 1000 patients completed this study. The PLMA proved to be an effective airway device: pro­viding PPV, with 100% success rate of PLMA inser­tion and gastric tube placement and decreased inci­dence of complications during intraperitoneal and ex­tra peritoneal laparoscopic surgeries as reported by previous workers. [7],[8],[9],[10],[11],[12],[13],[14]

The fibreoptic view from the drain tube revealed an open upper oesophageal sphincter (UOS) in 1.27% of patients which is in conformity with earlier studies. [17] It has been suggested that the open UOS may result from reflex relaxation, mechanical stretch or due to exposure to the atmosphere. [17] One patient had se­vere down-folding of epiglottis and the other had bi­lateral infolding of the PLMA cuff partly covering the glottis.

Optimal oxygenation and ventilation was noted in all patients before CO 2 insufflation. Transient subopti­mal oxygenation (SpO 2 - 94%) with EtCO 2 peaking at 80 mm Hg was seen in a patient undergoing total extraperitoneal inguinal hernia repair who developed extensive subcutaneous emphysema due to trocar mis­placement in the post insufflation period. [18] Two other patients with EtCO 2 exceeding 55 mm Hg in the post CO 2 insufflation period had severe down-folding of epi­glottis in one patient and bilateral medial in-folding of the mask in another. Severe down-folding of the epig­lottis impeding the ventilatory function has been reported earlier. [17] All regained normal values following CO 2 - desufflation at the end of the procedure.

There was no intraoperative displacement of the device. One important feature of PLMA is to prevent gastric insufflation due to the better oropharyngeal seal pressures. Five of our patients had gastric insufflation, not hindering surgery. The reported incidence of gas­tric insufflation is 0.1 percent. [17] However it was higher (0.5%) in our patients and might have resulted from PPV during mask ventilation before PLMA insertion. Our patients had low volume gastric aspirate because they were fasting, pain free before or during induction of anaesthesia, received drugs to reduce volume and raise pH of gastric contents. The intraoperative inci­dence of gastric regurgitation (2.5%) decreased over the period of study and it appears to be linearly influ­enced by frequency of usage. Though three cases of pulmonary aspiration have been reported following PLMA use in laparoscopic surgery, [19],[20],[21] there was no case of pulmonary aspiration in our study. Various stud­ies suggest that aspiration can be prevented by cor­rectly placed PLMA. [4],[5],[6] Meticulous selection of pa­tients and surgical procedures, optimal management of the placement, maintenance and emergence phases, and use of the PLMA can reduce the risk of aspiration. [22]

The PLMA formed an effective seal around the glottis in our patients (mean OLP 36 cm of H 2 O). This result is in accordance with previous work. [2],[3],[7],[8],[9],[10],[11],[12],[13],[14] The proper selection of the size of the PLMA is important for obtaining adequate seal and thereby improving the safety during laparoscopic surgery. Size 3 PLMA is considered a paediatric version in the Caucasian popu­lation, but was found appropriate in 42.95 % of our adult Indian female population. We found that the PIP increased significantly (not more than 50% of its origi­nal value) after creation of carboperitoneum without impairing the oropharyngeal seal. An OSP twice the PIP before institution of carboperitoneum proved to be a good predictor of the suitability of the device.

Tracheal intubation, considered ideal for laparoscopic procedures is not foolproof against aspi­ration of gastric contents. Young and Ridley demon­strated that the inflated high volume low pressure cuff of an endotracheal tube develops longitudinal folds and pooled secretions above can trickle down to the lower airways. [23] Warner and colleagues reported 32.9% cases of aspiration during direct laryngoscopy for intu­bation and 35.9% during extubation. [24]

There are no large series regarding the incidence of aspiration, with PLMA and comparative data with cLMA, in laparoscopic surgery. Cook estimated that 1.3 million patients would be required in each study group to determine if the incidence of aspiration was to be brought down to 50 % for PLMA as compared to cLMA. [25]

Lu and colleagues confirmed adequate airway management and ventilation with PLMA during carboperitoneum for laparoscopic cholecystectomy. [7] Other workers reported similar results for other laparoscopic procedures. [8],[9],[10],[11],[12],[13],[14] Maltby and colleagues in a comparative study involving 109 patients undergoing laparoscopic cholecystectomy reported that the PLMA provided equally effective ventilation as the tracheal tube, without clinically significant gastric distension and smoother emergence in non-obese patients. [8] In another study, Maltby reported a similar incidence of gastric distension in laparoscopic cholecystectomy managed with the cLMA or tracheal intubation. [26]

Obese patients are expected to have reduced tho­racic compliance, increased inspiratory resistance, higher incidence of difficult airways, failed intubation and greater risk of regurgitation. [27] The PLMA permits high inflation pressure without leak and its performance is superior to the cLMA in these patients. PLMA use has been reported in obese patients with BMI as high as 47-65 kg m -2 . Brain reported increased BMI to be associated with increased OSP. [2] Although proper po­sitioning of PLMA may be difficult as compared to cLMA, it improves with experience and confirmatory tests. [2],[3] as substantiated by Keller and colleagues who reported that PLMA provides an adequate short-term airway in grossly and morbidly obese patients, though its use was not justified for long duration procedures for lack of existing evidence. [28]

Natalini and colleagues showed that there is no clinically significant difference in pulmonary ventilation between obese and non-obese adult patients when the device is correctly placed but higher cuff pressures (>100 cm H 2 O) are required in obese patients to mini­mize leaks. [29] In the present study, 123 patients had BMI > 30 kg m-2 including 7 patients with a BMI>40kg m -2 . We used bougie-guided insertion electively in these seven patients. None of these patients had any episode of hypoxia or hypoventilation and OSP maintenance did not require any increase in intracuff pressure.

Blood was detected in 2.9 % of our patients with higher incidence in males (P = 0.02) and increased num­ber of attempts (P > 0.5). This is lower than the re­ported incidence of 18.2 percent. [17] The overall low rate of complaints of sore throat and dysphagia in our study may be explained by the limitation of cuff pres­sures to a maximum of 60 cm H 2 O as recommended by the manufacturer. [3]

Our study has a number of limitations: It is a de­scriptive study, with no randomized controls, and com­prised several variables (patient characteristics, differ­ent surgical procedures and patient positions). The in­clusion of obese patients (seven patients with BMI > 40 kg m -2 ) in the study is incidental because of con­secutive entry.

Although safety of the PLMA for laparoscopic surgery, is debatable, it is a better option than a cLMA. [30] Tracheal intubation remains the gold standard in pa­tients for emergency surgery with increased risk of as­piration. The PLMA has been used for laparoscopic and conventional abdominal surgery, in obese patients and for the management of elective and rescue difficult airways. Our study supports the safety of this device in commonly performed laparoscopic procedures as it successfully isolated the respiratory from the gas­trointestinal tract. We conclude that in experienced hands and following a strict protocol of insertion, the PLMA is an efficient and safe tool for airway manage­ment of elective fasting patients undergoing endoscopic laparoscopic abdominal surgery.

 
   References Top

1.Miller DM. A Proposed Classification and Scoring Sys­tem for Supraglottic Sealing Airways: A Brief Review. Anesth Analg 2004; 99: 1553-9.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]  
2.Brain AIJ, Verghese C, Strube PJ. The LMA 'ProSeal' - a laryngeal mask with an oesophageal vent. Br J Anaesth 2000; 84: 650-4.  Back to cited text no. 2      
3.Keller C, Brimacombe J. Mucosal pressure and oropha­ryngeal leak pressure with the ProSeal versus laryngeal mask airway in anaesthetized paralysed patients. Br J Anaesth 2000; 85: 262-6.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]  
4.Evans NR, Gardner SV, James MF. ProSeal laryngeal mask protects against aspiration of fluid in the pharynx. Br J Anaesth 2002; 88: 584-7.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]  
5.Miller DM, Light D. Laboratory and clinical comparisons of the Streamlined Liner of the Pharynx Airway (SLIPATM) with the laryngeal mask airway. Anaesthesia 2003; 58: 136-42.  Back to cited text no. 5  [PUBMED]    
6.Keller C, Brimacombe J, Kleinsasser A, Lockinger A. Does the ProSeal laryngeal mask airway prevent aspiration of regurgitated fluid? Anesth Analg 2000; 91:1017-20.  Back to cited text no. 6      
7.Lu PP, Brimacombe J, Yang C, Shyr M. ProSeal versus the classic laryngeal mask airway for positive pressure ven­tilation during laparoscopic cholecystectomy. Br JAnaesth 2002; 88: 824-7.  Back to cited text no. 7      
8.Maltby JR, Beriault MT, Watson NC, Liepert D, Fick GH. The LMA-ProSealTM is an effective alternative to tra­cheal intubation for laparoscopic cholecystectomy. Can J Anesth 2002; 49: 857-62.  Back to cited text no. 8  [PUBMED]    
9.Natalini G, Lanza G, Rosano A, Dell'Agnolo P, Bernardini A. Standard Laryngeal Mask Airway and LMA-ProSeal during laparoscopic surgery. J Clin Anesth 2003; 15: 428­32.  Back to cited text no. 9  [PUBMED]  [FULLTEXT]  
10.Garcia-Aguado R, Vivo BenllochM, Zaragoza Fernandez C, Garcia Solbes JM. ProSeal Laryngeal Mask for Laproscopic Cholecystectomy. Rev Esp Anestesiol Reanim 2003; 50: 55-7.  Back to cited text no. 10      
11.Roth H, Genzwuerker HV, Rothhaas A, Finteis T, Schmeck J. The ProSeal laryngeal mask airway and the laryngeal tube Suction for ventilation in gynaecological patients undergoing laparoscopic surgery. Eur J Anaesthesiol 2005; 22: 117-22.  Back to cited text no. 11  [PUBMED]    
12.Maltby JR, Beriault M, Watson NC, Liepert D, Fick GH. LMA-Classic TM and LMA ProSeal TM are effective alter­natives to endotracheal intubation for gynecological laparoscopy. Can J Anesth 2003; 50: 71-7.  Back to cited text no. 12      
13.Piper SN, Triem JG, Rohm KD, Maleck WH, Schollhorn TA, Boldt J. ProSeal-laryngeal mask versus endotracheal intubation in patients undergoing gynaecologic laparoscopy. Anasthesiol Intensivmed Notfallmed Schmerzther 2004; 39: 132-7.  Back to cited text no. 13      
14.Sinha A, Sharma B. Sood J. ProSeal TM as an alternative to endotracheal intubation in pediatric laparoscopy. Pediatr Anesth 2007; 17: 327-32.  Back to cited text no. 14      
15.Keller C, Brimacombe J, Puhringer F. A fibreoptic scoring system to assess the position of laryngeal mask devices. Inter-observer variability and a comparison between the standard, flexible and intubating laryngeal mask airway. Anasthesiol Intensivmed Notfallmed Schmerzther 2000; 35: 692-4.  Back to cited text no. 15      
16.Brimacombe J, Keller C. The ProSeal laryngeal mask air­way: a randomized, crossover study with the standard laryngeal mask airway in paralysed, anesthetized patients. Anesthesiology 2000; 93: 104-9.  Back to cited text no. 16  [PUBMED]  [FULLTEXT]  
17.Brimacombe J. Laryngeal Mask Anesthesia. Principle and Practice, 2nd ed. London: WB Saunders, 2005.  Back to cited text no. 17      
18.Singh K, Singhal A, Saggar VR, Sharma B and Sarangi R. Subcutaneous carbon dioxide emphysema following endoscopic extraperitoneal hernia repair: Possible mecha­nisms. J Laparoendosc Adv Surg Tech 2004; 14: 317-20.  Back to cited text no. 18      
19.Brimacombe J, Keller C. Aspiration of gastric contents during use of a ProSeal TM laryngeal mask airway secondary to unidentified fold over malposition. Anesth Analg 2003; 97: 1192-4.  Back to cited text no. 19  [PUBMED]  [FULLTEXT]  
20.Putzke C, Max M, Wulf H. Severe ARDS following perioperative aspiration of gastric content with the use of a "ProSeal" laryngeal mask airway. Anasthesiol Intensivmed Notfallmed Schmerzther 2005; 40: 487-9.  Back to cited text no. 20  [PUBMED]  [FULLTEXT]  
21.Koay CK. A case of aspiration with the ProSeal LMA (Letter). Anaesth Intensive Care 2003; 31: 123.  Back to cited text no. 21  [PUBMED]    
22.Keller C, Brimacombe J, Bittersohl J, Lirk P and Goedecke A V. Aspiration and the laryngeal mask airway: three cases and a review of the literature. Br J Anaesth 2004; 93: 579­82.  Back to cited text no. 22      
23.Young PJ, and Ridley S.A. Ventilator-associated pneu­monia. Diagnosis, pathogenesis and prevention. Anaes­thesia 2000; 55: 96-7.  Back to cited text no. 23      
24.Warner MA, Warner ME, Weber JG. Clinical significance of pulmonary aspiration during the preoperative period. Anesthesiology 1993; 78: 56-62.  Back to cited text no. 24  [PUBMED]  [FULLTEXT]  
25.Cook TM. cLMA and PLMA for laparoscopic surgery. Can J Anesth 2003; 50: 965-66.  Back to cited text no. 25      
26.Maltby JR, Micheal T, Neil C. Gorden H. Gastric disten­sion and ventilation during laparoscopic cholecystec­tomy: LMA-Classic vs. tracheal intubation. Can J Anesth 2000;47: 622-26.  Back to cited text no. 26      
27.Sprung J, Whalley DG, Falcone T, Warner DO, Hubmayr RD, Hammel J. The impact of morbid obesity, pneumo­peritoneum, and posture on respiratory system mechan­ics and oxygenation during laparoscopy. Anesth Analg 2002; 94: 1345-50.  Back to cited text no. 27  [PUBMED]  [FULLTEXT]  
28.Keller C, Brimacombe J, Kleinsasser A, Brimacombe L. The laryngeal mask airway ProSeal TM as a temporary ven­tilatory device in grossly and morbidly obese patients before laryngoscope-guided tracheal intubation. Anesth Analg 2002; 94: 737-40.  Back to cited text no. 28  [PUBMED]  [FULLTEXT]  
29.Natalini G, Franceschetti ME, Pantelidi MT, Rosano A, Lanza G, and Bernardini A. Comparison of the standard laryngeal mask airway and the ProSeal laryngeal mask airway in obese patients. Br J Anaesth 2003; 90: 323-6.  Back to cited text no. 29      
30.Cooper RM. The LMA, laparoscopic surgery and the obese patient- can vs should. Can J Anesth 2003; 50: 5-10.  Back to cited text no. 30  [PUBMED]    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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