Comparison of the Endotracheal Tube and Laryngeal Mask in Airway Management by Paramedical Personnel ~

John H. Pennant,

MA, MB, BS, FCAnaes,

and Martin B. Walker,

MB, BS, FCAnaes

Department of Anesthesiology, University of Texas Southwestern Medical School, Dallas, Texas

An evaluation of the laryngeal mask airway (LMA) as a means of airway support when used by paramedical personnel was performed. Forty medical and paramedical students attempted to intubate the tracheas of 40 healthy anesthetized adults with the LMA and a cuffed endotracheal tube (ETT). The number of attempts to achieve correct placement and the time taken to adequately ventilate the lungs were recorded for both devices. End-tidal carbon dioxide was detected significantly sooner after commencement of the intubation attempt using the LMA (mean 38.6 s) compared with the ETT (mean 88.3 s, P < 0.0001). Ninety-four percent of the students successfully ven-

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he laryngeal mask airway (LMA, Figure 1) is a novel device that has found widespread popularity in Europe and Australia for airway management under general anesthesia (14). It has been successfully used in circumstances where conventional endotracheal intubation proved difficult or impossible (5-8), including obstetric practice (9-1 1).The LMA is inserted blindly, without the use of a laryngoscope, and is easy to correctly position atraumatically so as to support the airway. Tracheal intubation with a cuffed tube is the standard for emergency airway management but requires skill and continuous experience. Although most evaluations of the LMA have studied the performance of anesthesiologists with no prior experience with the device (2,8), only one trial has assessed the performance of inexperienced personnel in its placement (121. We studied a group of paramedical and medical students to determine if the LMA could be a useful adjunct to resuscitation in a North American setting where trauma is so prevalent.

Accepted for publication November 26, 1991. Address correspondence to Dr. Pennant, Department of Anesthesiology, University of Texas Southwestern Medical School, 5323 Harry Hines Boulevard, Dallas, TX 75235-9068. 01992 by the International Anesthesia Research Societv 0003-2999/92/$5.00

tilated the lungs on their first attempt with the LMA, whereas only 6970 intubated the trachea on their first attempt with the ETT ( P < 0.01). Five students were unable to intubate the trachea after three attempts with the ETT, but all positioned the LMA satisfactorily on their first try in a mean time of 40 s. We conclude that unskilled operators with minimal training can safely and successfully ventilate unconscious patients more rapidly using the LMA than the ETT. These results suggest the LMA should be available in all areas where resuscitation is performed. (Anesth Analg 1992;74:5314)

Methods After Institutional Review Board approval of the protocol was received, informed written consent was obtained from 40 ASA physical status I and I1 patients aged 18-65 yr. All were scheduled to undergo elective surgery in which the trachea was to be intubated. Patients were excluded if they posed a risk of regurgitation of gastric contents during induction of anesthesia (e.g., body weight >lo0 kg, pregnancy, or any emergency procedure where it could not be assumed that the stomach was empty). Patients likely to pose problems in airway establishment because of limited mouth opening or reduced mobility of the cervical spine were similarly excluded. Forty paramedical and senior medical students with minimal or no intubation experience were given brief instructions on the use of the endotracheal tube (ETT) and of the LMA. The guidelines for using the LMA were based on the instruction manual available from the manufacturer (D. J. Colgate Medical Limited, Windsor, England). After premedication with ranitidine 150 mg and sodium citrate 30 mL orally and after breathing 100% oxygen for 3 min, anesthesia was induced with thiopental 5 mgikg and fentanyl 2 pgikg intravenously. Neuromuscular blockade was established using vecuronium 0.1 mgikg. The electrocardiogram, capnograph, and finger pulse oximetry were continAnesth Analg 1992;74:5314

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stopped and restarted when the device was again handed to the student after a further period of mask ventilation. A maximum of three attempts to intubate the trachea was permitted for each device. Any complications of the procedure were noted, and all patients were visited postoperatively for assessment.

Results

Figure 1. A size 4 LMA with its cuff partiallv inflated

uously monitored, and arterial blood pressure was measured noninvasively every minute. Ventilation via a bag and mask was performed manually during 1% isoflurane anesthesia until muscle paralysis was demonstrated using a peripheral nerve stimulator. A size-3 or -4 LMA and a 7-or 8-mm cuffed ETT were selected based on the patient’s weight. The time taken to intubate the trachea and provide adequate ventilation was measured from the moment the student held either the LMA or a laryngoscope in his hand until expired carbon dioxide at a value >25 mm Hg was detected by the capnograph after manual compression of the reservoir bag. Each student intubated the trachea of one patient with both devices in random order as determined by a table of random numbers. Ventilation of the lungs was further confirmed by one of the investigators by chest auscultation. After satisfactory insertion, the first device was removed by the investigator and the patient’s lungs were once again ventilated by bag and mask for 1 min before an attempt with the other device was begun. Advice and help were given, if necessary, during intubation. If at any time arterial oxygen saturation decreased below 90%, or other cardiovascular variables departed more than 20% from baseline values, the procedure was abandoned and mask ventilation was resumed until, at the discretion of the investigator, a further attempt was made. In the case of an ETT or LMA insertion resulting in failure, the clock was

The patients’ ages ranged from 18 to 65 yr (mean 37 yr) and their weights ranged from 47 to 99 kg (mean 69 kg). No student had prior experience with the LMA, and 16 had never previously used an ETT. The remainder had intubated the tracheas of 1-8 patients (mean 1.5) in the past. Some paramedical students had practiced endotracheal intubation on a manikin. Five students were excluded from statistical analysis because they failed to successfully intubate the trachea in three attempts using the ETT. Of the 35 trainees remaining in the study, 33 (94%) correctly positioned the LMA on their first attempt; the other two (6%) were successful on their second attempt. Twenty-four (69%) successfully intubated with the ETT on their first attempt, 10 (2970)on their second, and one on the third attempt. The times for LMA insertion ranged from 21 to 90 s (mean 38.6 s, SD 14), whereas those for the ETT ranged from 30 to 210 s (mean 88.3 s, SD 49). Because the sampling delay using the “SARAcap” capnograph amounted to 7 s, that time is reflected in the times for both LMA and ETT insertions. Using a correlated t-test, it was determined that insertion of the LMA was significantly quicker than endotracheal intubation (t = 6.3886, P < 0.0001). Interestingly, the five students who were excluded all inserted the LMA successfully on their first attempt in 26-72 s (mean 40 s). All had failed to intubate after three attempts with the ETT, despite taking 210-420 s. We were impressed that those using the ETT needed far more advice and guidance than those using the LMA. We also noticed minimal changes in cardiovascular variables when the LMA was used compared with an ETT. However, we did not study this phenomenon, which has been described by other workers (13). No problems attributable to the LMA were noted. After endotracheal intubation, one patient became tachycardic and bronchospasm developed in one. A gas leak around the LMA cuff was occasionally noted at airway pressures above 15 cm H,O, although adequate ventilation was easily achieved.

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Discussion The care given during the "golden hour" after trauma is the most crucial determinant of eventual outcome (14). Patient management during this critical period often lies in the hands of paramedical personnel. The primary goal in resuscitation is to establish a patent airway to allow adequate oxygenation, yet prevent pulmonary aspiration of blood and vomitus. To date, the cuffed ETT has fulfilled this role in the unconscious or apneic victim. Acquisition of the skill of tracheal intubation requires extensive training, and valuable time may be wasted in the field by repeated attempts to successfully place a tube in the trachea. During this period, ventilation of the lungs may not occur, and the ensuing hypoxemia can profoundly affect survival. The LMA is a rapid and effective means of ventilating unconscious patients when used by anesthesiologists ( 2 4 ) , but it has not been evaluated in the hands of paramedical personnel who may have difficulty establishing an adequate airway. In one British study of naval medical technicians, satisfactory ventilation was achieved with the LMA in about 40 s in 94% of cases although each participant was evaluated on 10 or more insertions, and all had undergone prior training using videotapes, manikins, and a clinical demonstration (12). Interestingly, their performance using the LMA did not improve with experience, and remained above 90% for a11 attempts, whereas their scores using the ETT improved from no successful insertions on the first attempt to 80% on the tenth attempt. Our study differed in that we evaluated paramedical and medical students on only one intubation with each device, and none had more than 1 min of instruction on their use. Our subjects also correctly positioned the LMA more rapidly than an ETT (38.6 vs 88.3 s) and were more likely to succeed on their first attempt (9470 vs 69%). The lungs of all patients in our study were ventilated using the LMA within 90 s, but the tracheas of five patients could not be intubated despite three attempts in a time period of 3.5-7.0 min. We excluded patients in whom airway difficulties might be encountered. However, others have shown the LMA to be a useful adjunct in these situations (7,9,10,15); further controlled studies in this area would be valuable. We did not seek confirmation of correct placement of these devices by fiberoptic bronchoscopy. This would be unrealistic in the field situation. Downfolding of the epiglottis has frequently been observed when a bronchoscope is passed through the LMA (16), yet ventilation is still possible in most cases. Here, the bronchoscopic view might be misleading and indicate an unsatisfactory LMA position.

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One troubling aspect of the LMA is that it does not reliably protect the airway. Aspiration around the LMA cuff has been reported (17), although dye studies have shown this to be a rare event (18). A nasogastric tube may be easily passed behind the LMA to empty the stomach in situations where there is a risk of aspiration (19). Nevertheless, until further investigations have been performed, the use of the LMA as a primary method of airway management in the trauma victim must remain questionable. Once the LMA is in place, it is possible to introduce a 6.0-mm ETT through the LMA and intubate the trachea (19,20), or pass a bougie or fiberoptic bronchoscope and railroad an ETT over it to achieve the same results (21,22). These maneuvers may be performed if there is concern over airway protection in the trauma patient. Our study involved only healthy, paralv7rd, nonobese adults with empty stomachs, so its appll cability to the trauma situation can only be sprculative. In this preliminary study, we believed it unethical to investigate trauma victims until the safety of the LMA had been confirmed in a healthy population. The LMA should not replace the ETT as a first-line device for airway support in trauma unless, because of inexperience or anatomical abnormalities, tracheal intubation is impossible. The role of the LMA in the trauma patient needs to be defined. Use of the esophageal obturator airway by paramedics requires little training and may have produced similar results to ours. However, it is more traumatic to insert, is associated with more complications, and is not available in pediatric sizes (23). A comparison of the esophageal obturator airway with the LMA in trauma needs to be performed. In conclusion, we have shown the LMA to be a more effective means of airway management than the ETT when used by inexperienced personnel in healthy elective surgery patients. It is the authors' belief that the LMA should be available as an alternative to tracheal intubation in all areas where resuscitation and anesthesia are carried out, as it may reduce the tragic morbidity and mortality from hypoxemia when there is difficulty in establishing an airway using conventional methods. Further studies are indicated to clarify its role in these situations whether used by medical or paramedical personnel.

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ence with the laryngeal mask airway in tw'o hundred patients. Anaesth Intensive Care 1991;19:25f3-40. Maltby IR, Loken RG, Watson NC. The laryngeal mask airway: clinical appraisal in 250 patients. Can J Anaesth 1990;37:509-13. Calder 1, Ordman A], Jackowski A, Crockard HA. The Brain laryngeal mask airway. An alternative to emergency tracheal intubation. Anaesthesia 1990;45:137-9. Thomson KD, Ordman AJ, Parkhouse N, Morgan BDG. Use of the Brain layngeal mask airway in anticipation of difficult tracheal intubation. Br J Plast Surg 1989;42:47%80. Brain All. Three cases of difficult intubation overcome by the laryngeal mask airway. Anaesthesia 1985;40:353-5. Alexander CA, Leach AB, Thompson AR, Lister JB. Use your Brain? Anaesthesia 1988;43:89W. McClune S, Regan M, Moore J. Laryngeal mask airway for caesarean section. Anaesthesia 1990;45:227-8. Chadivick IS, Vohra A. Anaesthesia tor emergency caesarean section using the Brain laryngeal airway. Anaesthem 1989;11: 261-2. King TA, Adams AP. Failed intubation. Br J Anaesth 1990;65: 40&14. Davies PRF, Tighe SQM, Greenslade GL, E\rans G H . Laryngeal mask airway and tracheal tube insertion by unskilled personnel. Lancet 1990;ii:977-9. Braude N, Clements EAF, Hodges UM, Andreivs BP. The

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pressor response and laryngeal mask insertion. A comparison with tracheal intubation. Anaesthesia 1989;44:551-4. Stene JK, Grande CM, Giesecke A. Shock resuscitation. In: Stene JK, Grande CM, eds. Trauma anesthesia. Baltimore: Williams & Wilkins, 1991:lOO-32. Allen JG, Flower EA. The Brain laryngeal mask. An alternative to difficult intubation. Br Dent J 1990;168:2024. Payne J . The use of the fibreoptic laryngoscope to confirm the position of the laryngeal mask. Anaesthesia 1989;44:865. Griffin RM, Hatcher IS. Aspiration pneumonia a n d the laryngeal mask airway. Anaesthesia 1990;45:103940. John RE, Hill S, Hughes TJ. Airway protection by the laryngeal mask. A barrier to dye placed in the pharynx. Anaesthesia 1991;46:36&7. Brain AIJ. Further developments of the laryngeal mask. Anaesthesia 1989;44:530. Heath ML, Allagain J. The Brain laryngeal mask airway as a n aid to intubation. Br J Anaesth 1990;64:382P-3P. McCrirrick A, Pracilio JA. Awake intubation: a new technique. Anaesthesia 1991;46:661-3. Allison A, McCrorv J. Tracheal placement of a g u m elastic bougie using the laryngeal mask airway. Anaesthesia 1989;44: 119-20. Schwartz AJ, Campbell FW. Cardiopulmonary resuscitation. In: Barash PG, Cullen BF, Stoelting RK, eds. Clinical anesthesia Philadelphia: Lippincott, 1989:1477-515.

Comparison of the endotracheal tube and laryngeal mask in airway management by paramedical personnel.

An evaluation of the laryngeal mask airway (LMA) as a means of airway support when used by paramedical personnel was performed. Forty medical and para...
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