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Poor Man's LMA: achieving adequate ventilation with a poor mask seal

From the Department of Anesthesiology, University of Alabama at Birmingham, Birmingham, Alabama, USA.

Address correspondence to: Dr. James R. Boyce, University of Alabama at Birmingham, Department of Anesthesiology, JT845, 619 South 19^th Street, Birmingham, Alabama 35249-6810, USA. Phone: 205-934-6948; Fax: 205-975-3080; E-mail: kathryn.campbell{at}ccc.uab.edu

	Abstract

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Purpose: This report describes a technique of ventilation prior to laryngoscopy and intubation that proved to be simple, inexpensive and effective for a patient whose airway evaluation suggested difficult mask ventilation. The technique is called Poor Man's LMA.

Clinical features: A 60-yr-old male, measuring 170 cm, weighing 117 kg, edentulous and with a full beard, was to undergo uvulopalatopharyngoplasty. After induction of general anesthesia with a hypnotic, analgesic and non-depolarizing muscle relaxant, it was soon determined that mask bag ventilation was difficult due to an inadequate seal between the mask and the patient's full beard. To improve ventilation, an endotracheal tube was placed into the oropharynx, the lips and nose compressed by a colleague in order to prevent gas egress, and effective manual ventilation established by connecting the circle system to the endotracheal tube. Subsequent direct laryngoscopy and intubation were accomplished without incident.

Conclusion: The patient's clinical features made conventional mask bag ventilation difficult and inadequate. The Poor Man's LMA technique improved oxygenation and ventilation in preparation for intubation. Further investigations on the usefulness of this technique are warranted.

OCCASIONALLY during induction of general anesthesia, the anesthesiologist discovers that the patient is very difficult to ventilate with mask and bag. In the absence of any obstructive supraglottic pathology and with adequate neuromuscular blockade eliminating the possibility of laryngospasm, the difficulty often is due to a poor mask fit and inadequate seal. In spite of oral and nasal pharyngeal airways, optimal oxygen saturations are not achieved because of insufficient tidal volumes. The following case illustrates the use of a ventilation technique called the Poor Man's LMA that improved pre-intubation oxygenation by more than doubling the tidal volumes.

	Case presentation

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A 60-yr-old male measuring 170 cm, with a body mass index (BMI) of 40.4, a full beard and a history of nocturnal snoring, was scheduled for uvulopalatopharyngoplasty under general endotracheal anesthesia. He was edentulous and, on religious grounds, preferred to keep his full beard intact. His Mallampati classification of I, head extension of 40, and hyomental distance of three fingerbreadths, suggested easy endotracheal intubation. He had no stridor or any physical findings suggestive of upper airway obstruction. After appropriate monitor placement and oxygenation, the OR table was placed in 20 reverse Trendelenburg tilt and anesthesia was induced with sodium thiopental 500 mg, fentanyl 250 µg, and rocuronium 50 mg, administered intravenously. Attempts at mask and bag ventilation were unsuccessful because of the air leak due to the beard and facial deformities seen in patients without teeth. Maximum tidal volumes were 235 ml in spite of liberal use of the oxygen flush. Oxygen saturations declined from pre-induction values of 100% to the low 90's in two to three minutes.

A 7.5 cuffed endotracheal tube was placed into the patient's mouth and advanced into the oropharynx so the cuffed portion of the tube was between the tongue and the posterior pharyngeal wall (Figure 1). The cuff was inflated and the 15 mm connector attached to the circle system. As shown in Figure 2, the patient's alae nasae were compressed and lips opposed to make a seal around the tube. A colleague squeezed the bag as if the patient were intubated, expanding the chest. End tidal CO₂, measured tidal volumes of 700 ml to 900 ml and a return of O₂ saturation to 100% all indicated optimal ventilation. The patient was easily intubated and the case concluded without further incident.

View larger version (20K): [in this window] [in a new window]   FIGURE 1 The cuffed endotracheal tube is placed in the oropharynx behind the tongue. The distal end of the tube is above the glottic opening.

View larger version (18K): [in this window] [in a new window]   FIGURE 2 The patient's alae nasae are compressed and the lips opposed to make a seal around the endotracheal tube. Egress is prevented with positive pressure from the circle system and ventilation is established.

	Discussion

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The consequences of inadequate ventilation by mask prior to intubation are grave since dangerously low levels of oxygen saturation can quickly occur. Furthermore, if attempts at intubation are difficult and unsuccessful, the clinical scenario of ‘cannot ventilate cannot intubate’ becomes exigent demanding rescue manoeuvers to include laryngeal mask airway, combitube insertion, transtracheal jet ventilation, or establishment of a surgical airway as recommended by the updated ASA algorithm for the management of the difficult airway.⁴ These procedures, particularly transtracheal jet ventilation and a surgical airway are not without their own risks, particularly in the setting of a clinical crisis.

The key to avoiding adverse outcomes that begin on induction with inadequate ventilation by mask is to have alternative techniques of ventilation immediately available. In addition to the laryngeal mask airway and combitube, the technique described in this case report offers an additional solution to failed mask and bag ventilation when the failure is due to problems of maintaining a seal. The presence of a beard, or altered facial anatomy can hinder a proper mask fit mandating another mode of ventilation to offset the declining oxygen saturation.

Before the Poor Man's LMA is considered as an option, it is important to distinguish two separate categories of difficult mask ventilation. One category consists of anatomical variations that prevent good application of the mask to the face to establish an effective seal. This case presentation is such an example, and the use of the Poor Man's LMA technique may be appropriate. The other category consists of patients determined to be difficult to ventilate by mask due to significant glottic or supraglottic pathology that obstructs or potentially obstructs airflow. Often these patients manifest stridor and supraclavicular-intercostal indrawing. In these patients who have obstruction or even potential obstruction, the Poor Man's LMA technique would be contraindicated and preemptive placement of a cricothyrotomy catheter⁶ or awake fiberoptic intubation would be preferable procedures of choice.

The use of intermediate acting non-depolarizing muscle relaxants warrants discussion. In cases where direct laryngoscopy and intubation are predicted to be a challenge but not impossible, successful intubation is sometimes complicated because extra time is required to secure the airway. The longer time afforded by use of intermediate acting non-depolarizing muscle relaxants, compared to succinylcholine, optimizes conditions for successful airway management particularly when intermittent ventilation is required to maintain safe levels of oxygenation during multiple intubation attempts.

In summary, this report describes the use of an oropharyngeally placed endotracheal tube to allow, with the assistance of a colleague, manual ventilation of the lungs in a patient who proved to be impossible to ventilate with a conventional face mask during induction of anesthesia. The technique, nicknamed "Poor Man's LMA," may be used when specific devices such as the LMA or Combitube are not available and warrants further investigation.

Accepted for publication January 16, 2001.

	References

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1 Crosby ET, Cooper RM, Douglas MJ, et al. The unanticipated difficult airway with recommendation for management. Can J Anaesth 1998; 45: 757–76.[Abstract/Free Full Text]

2 Brimacombe J, Berry A. The laryngeal mask airway – the first ten years. Anaesth Intensive Care 1993; 21: 225–6.[Medline]

3 Langeron O, Masso E, Huraux C, et al. Prediction of difficult mask ventilation. Anesthesiology 2000; 92: 1229–36.[Medline]

4 Benumof JL. Laryngeal mask airway and the ASA difficult airway algorithm. Anesthesiology 1996; 84: 686–99.[Medline]

5 Boyce JR, Peters G. Vessel dilator cricothyrotomy for transtracheal jet ventilation. Can J Anaesth 1989; 36: 350–3.

This article has been cited by other articles:

				J.-H. Bahk Management of the anesthetized but cannot-ventilate' situation Can J Anesth, November 1, 2001; 48(10): 1047 - 1047. [Full Text] [PDF]

				K. Lalwani ""Poor Man's LMA"" Can J Anesth, November 1, 2001; 48(10): 1047 - 1048. [Full Text] [PDF]

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