anesth analg 1992 pennant 531 4 (1)

7/28/2019 Anesth Analg 1992 Pennant 531 4 (1)

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Comparisonof the Endotracheal Tubeand Laryngeal Mask~in Airway Managementby Paramedical Personnel

J ohnH. Pennant, MA, MB, BS, FCA naes, and Martin B. Walker, MB, BS, FCA naesDepartment of A nesthesiology, University of Texas Southwestern Medical School, Dallas, Texas

An evaluation of the laryngeal mask airway (LMA) asa means of airway support when used by paramedi-cal personnel was performed. Forty medical andparamedical students attempted to intubate the tra-cheasof 40healthy anesthetized adults with the LMAand a cuffed endotracheal tube (ET T). The number ofattempts to achieve correct placement and the timetaken to adequately ventilate the lungs were recordedfor both devices. End-tidal carbon dioxide was de-tected significantly sooner after commencement ofthe intubation attempt using the LMA (mean 38.6s)compared with the ETT (mean 88.3 s, P


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532 IFN\ANT AVD WALKERLARY Y GEAL MASK A IRWAY E VA LL AT IO h ANESTH ANALG1992;74:5314

Figure1. A size 4 LMA with its cuff partiallv inflated

uously monitored, and arterial blood pressure wasmeasured noninvasively every minute. Ventilationvia a bag and mask was performed manually during1% isoflurane anesthesia until muscle paralysis wasdemonstrated using a peripheral nerve stimulator.A size-3 or -4 LMA and a7-or 8-mm cuffed ETTwere selected based on the patients weight. The timetaken to intubate the trachea and provide adequateventilation was measured from the moment the stu-dent held either the LMA or a laryngoscope in hishand until expired carbon dioxide at a value>25 mm Hg was detected by the capnograph aftermanual compression of the reservoir bag. Each stu-dent intubated the trachea of one patient with bothdevices in random order as determined by a table ofrandom numbers. Ventilation of the lungs was fur-ther confirmed by one of the investigators by chestauscultation.After satisfactory insertion, the first device wasremoved by the investigator and the patients lungswere once again ventilated by bag and mask for 1minbefore an attempt with the other device was begun.Advice and help were given, if necessary, duringintubation.If at any time arterial oxygen saturation decreasedbelow 90%, or other cardiovascular variables de-parted more than 20% from baseline values, theprocedure was abandoned and mask ventilation wasresumed until, at the discretion of the investigator, afurther attempt was made. In the case of an ETT orLMA insertion resulting in failure, the clock was

stopped and restarted when the device was againhanded to the student after a further period of maskventilation. A maximum of three attempts to intubatethe trachea was permitted for each device. Anycomplications of the procedure were noted, and allpatients were visited postoperatively for assessment.

ResultsThe patients ages ranged from 18 to 65 yr (mean37 yr) and their weights ranged from 47 to 99 kg(mean 69 kg). No student had prior experience withthe LMA, and 16 had never previously used an ETT.The remainder had intubated the tracheas of 1-8patients (mean 1.5) in the past. Some paramedicalstudents had practiced endotracheal intubation on amanikin.

Five students were excluded from statistical anal-ysis because they failed to successfully intubate thetrachea in three attempts using the ETT. Of the 35trainees remaining in the study, 33 (94%) correctlypositioned the LMA on their first attempt; the othertwo (6%) were successful on their second attempt.Twenty-four (69%) successfully intubated with theETT on their first attempt, 10 (2970)on their second,and one on the third attempt.The times for LMA insertion ranged from 21 to 90s(mean 38.6 s, SD 14), whereas those for the ETTranged from30 to 210 s (mean 88.3s, SD 49). Becausethe sampling delay using the SARAcap capno-graph amounted to 7 s, that time is reflected in thetimes for both LMA and ETT insertions. Using acorrelated t-test, it was determined that insertion ofthe LMA was significantly quicker than endotrachealintubation ( t =6.3886, P


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ANESTH ANAL G199274:531 4 PENNA NT A ND W A L KER 533LARY NGEAL MASK A IRWAY EVAL UATION

DiscussionThe care given during the "golden hour" after traumais the most crucial determinant of eventual outcome(14). Patient management during this critical periodoften lies in the handsof paramedical personnel. Theprimary goal in resuscitation is to establish a patentairway to allow adequate oxygenation, yet preventpulmonary aspiration of blood and vomitus. To date,the cuffed ETT has fulfilled this role in the uncon-scious or apneic victim. Acquisition of the skill oftracheal intubation requires extensive training, andvaluable time may be wasted in the field by repeatedattempts to successfully place a tube in the trachea.During this period, ventilation of the lungs may notoccur, and the ensuing hypoxemia can profoundlyaffect survival.The LMA is a rapid and effective means of venti-lating unconscious patients when used by anesthesi-ologists (24), but it has not been evaluated in thehands of paramedical personnel who may have diffi-culty establishing an adequate airway. In one Britishstudy of naval medical technicians, satisfactory ven-tilation was achieved with the LMA in about40 s in94%of cases although each participant was evaluatedon 10or more insertions, and all had undergone priortraining using videotapes, manikins, and a clinicaldemonstration (12). Interestingly, their performanceusing the LMA did not improve with experience, andremained above 90% for a11attempts, whereas theirscores using the ETT improved from no successfulinsertions on the first attempt to 80% on the tenthattempt. Our study differed in that we evaluatedparamedical and medical students on only one intu-bation with each device, and none had more than1min of instruction on their use.Our subjects also correctly positioned the LMAmore rapidly than an ETT (38.6 vs 88.3s) and weremore likely to succeed on their first attempt (9470 vs69%). The lungs of all patients in our study wereventilated using the LMA within 90 s, but the tra-cheas of five patients could not be intubated despitethree attempts in a time period of 3.5-7.0 min.We excluded patients in whom airway difficultiesmight be encountered. However, others have shownthe LMA to be a useful adjunct in these situations(7,9,10,15); further controlled studies in this areawould be valuable.We did not seek confirmation of correct placementof these devices by fiberoptic bronchoscopy. Thiswould be unrealistic in the field situation. Downfold-ing of the epiglottis has frequently been observedwhen a bronchoscope is passed through the LMA(16), yet ventilation is still possible in most cases.Here, the bronchoscopic view might be misleadingand indicate an unsatisfactory LMA position.

One troubling aspectof the LMA isthat it does notreliably protect the airway. Aspiration around theLMA cuff has been reported (17), although dye stud-ies have shown this to be a rare event (18). Anasogastric tube may be easily passed behind theLMA to empty the stomach in situations where thereis a risk of aspiration (19). Nevertheless, until furtherinvestigations have been performed, the use of theLMA as a primary method of airway management inthe trauma victim must remain questionable.Once the LMA is in place, it is possible to intro-duce a 6.0-mm ETT through the LMA and intubatethe trachea (19,20), or pass a bougie or fiberopticbronchoscope and railroad an ETT over it to achievethe same results (21,22). These maneuvers may beperformed if there is concern over airway protectionin the trauma patient.Our study involved only healthy, paralv7rd,nonobese adults with empty stomachs, so its appllcability to the trauma situation can only be sprcula-tive. In this preliminary study, we believed it uneth-ical to investigate trauma victims until the safety ofthe LMA had been confirmed in a healthy popula-tion. The LMA should not replace the ETT as afirst-line device for airway support in trauma unless,because of inexperience or anatomical abnormalities,tracheal intubation is impossible. The role of the LMAin the trauma patient needs to be defined.Use of the esophageal obturator airway by para-medics requires little training and may have pro-duced similar results to ours. However, it is moretraumatic to insert, is associated with more complica-tions, and is not available in pediatric sizes (23). Acomparison of the esophageal obturator airway withthe LMA in trauma needs to be performed.In conclusion, we have shown the LMA to be amore effective means of airway management than theETT when used by inexperienced personnel inhealthy elective surgery patients. It is the authors'belief that the LMA should be available as an alter-native to tracheal intubation in all areas where resus-citation and anesthesia are carried out, as it mayreduce the tragic morbidity and mortality from hy-poxemia when there is difficulty in establishing anairway using conventional methods. Further studiesare indicated to clarify its role in these situationswhether used by medical or paramedical personnel.

References1. Brain A IJ . The laryngeal mask-a new concept in airwavmanagement. Br J Anaesth 1983;55:801-5.2. Broderick I'M, Webster NR , Nunn JF. The laryngeal maskairway. A study of 100patients during spontaneous breathing.A naesthesia 1989;44:23841.3. McCrirrick A, Ramage DTO, Pracilio ] A , Hickman J A .Fxperi-


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534 PENNANT AND WALKERLARYNGEALMASK A I R W A Y EVALUATIOS

ence wi th the laryngeal mask airway in tw'o hundred patients.A naesth Intensive Care 1991;19:25f3-40.4. M altby IR, L oken RG, W atson NC . The laryngeal mask airway:clinical appraisal in 250patients. Can A naesth 1990;37:509-13.5. Calder 1 Ordman A], Jackowski A , Crockard HA . The Brainlaryngeal mask airway. A n alternative to emergency trachealintubation. A naesthesia 1990;45:137-9.6. Thomson KD, O rdman AJ , Parkhouse N , M organ BDG. Use ofthe Brain layngeal mask airway in anticipation of diffi culttracheal i ntubation. Br J Plast Surg 1989;42:47%80.7. Brain Al l . Three cases of diff icult intubation overcome by thelaryngeal mask airway. Anaesthesia 1985;40:353-5.8. A lexander CA , Leach AB , Thompson A R, L ister J B. Use yourBrain? A naesthesia 1988;43:89W.9. McClune S, Regan M , Moore J . L aryngeal mask airway forcaesarean section. A naesthesia 1990;45:227-8.10. Chadivick IS, V ohra A . Anaesthesia tor emergency caesareansection using the Brain laryngeal airway. A naesthem 1989; 11:261-2.11. K ing TA , A dams AP . Failed intubation. Br J A naesth 1990;65:40&14.12. Davies PRF, Tighe SQM, Greenslade GL , E\rans GH. Laryn-geal mask airway and tracheal tube insertion by unskilled

personnel . Lancet 1990;ii:977-9.13. Braude N, Cl ements EAF, H odges UM , A ndreivs BP. The

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pressor response and laryngeal mask insertion. A comparisonwi th tracheal i ntubation. A naesthesia 1989;44:551-4.14. Stene J K , Grande CM , Giesecke A . Shock resuscitation. I n:Stene J K , Grande CM , eds. T rauma anesthesia. B altimore:Williams& Wilkins, 1991:lOO-32.15. A llen JG, Flower EA . The Brain laryngeal mask. A n alternativeto diff icult intubation. Br Dent J 1990;168:2024.16. Payne J . The use of the fibreoptic laryngoscopeto confirm theposition of the laryngeal mask. A naesthesia 1989;44:865.17. Griffin RM , Hatcher IS. A spiration pneumonia and the laryn-geal mask ai rway. A naesthesia 1990;45:103940.18. John RE, Hill S,Hughes T J . A irway protection by the laryngealmask. A barrier to dye placed in the pharynx. A naesthesia1991;46:36&7.19. Brain A I J . Further developments of the laryngeal mask.A naesthesi a 1989;44:530.20. Heath ML , A llagain J . The Brain l aryngeal mask airway as anaid to intubation. Br J A naesth 1990;64:382P-3P.21. M cCrirrick A, Pracilio J A . Aw ake intubation: a new technique.A naesthesia 1991;46:661-3.22. Al lison A , M cCrorv J . Tracheal placement of a gum elasticbougie usi ng the laryngeal mask ai rway. A naesthesia 1989;44:119-20.23. Schwartz A J , Campbell FW. Cardiopulmonary resuscitation.

In: Barash PG, Cullen BF, Stoelting RK, eds. C linical anesthe-sia Phi ladelphia: L ippincott, 1989:1477-515.

anesth analg 1992 pennant 531 4 (1)

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