A PROSPECTIVE EVALUATION OF CLINICAL-TESTS FOR PLACEMENT OF LARYNGEALMASK AIRWAYS

Background: Reliable tests of correct anatomic placement of the laryng eal mask airway (LMA) may enhance safety during use and minimize the n eed for fiberoptic instrumentation during airway manipulation through the device. This study assessed the correlation between the outcomes o f nine clinical tests to place the LMA and the anatomic position of th e device as graded on a standard fiberoptic scale. Methods: During 150 anesthetics, the outcome of nine clinical tests of correct placement was individually scored as satisfactory (positive) or unsatisfactory ( negative) for clinical use of the LMA. Anatomic placement was assessed (by fiberoptic evaluation) by an anesthesiologist, who was blinded to the placement of the device, as grade 1, vocal cords not seen; grade 2, cords plus the anterior epiglottis seen; grade 3, cords plus the po sterior epiglottis seen; and grade 4, only vocal cords seen. The outco mes of clinical tests were correlated with fiberoptic grade. Results: Tests that correlated with the fiberoptic grade were the ability to ge nerate an airway pressure of 20 cm water, the ability to ventilate man ually, a black line on the LMA in midline, anterior movement of the la rynx, outward movement of the LMA on inflation of the cuff, and moveme nts of the reservoir bag with spontaneous breathing. Two tests, abilit y to generate airway pressure of 20 cm water and ability to ventilate manually, correlated with fiberoptic grades 4 and 3 combined (i.e., th e epiglottis was supported by the LMA) and grade 2 (the epiglottis was not supported by the LMA). Tests with poor correlation with fiberopti c grade were the presence of resistance at the end of insertion, Inabi lity to advance LMA after inflation of the cuff, and presence of a cap nographic trace. Conclusions: The outcome of clinical tests correlates with the anatomic placement of LMAs, as judged by fiberoptic examinat ion. Two tests that best correlated with the fiberoptic grade were the ability to generate ah-way pressure of 20 cm water and the ability to ventilate manually.