ABSTRACT
Preoperative evaluation is important in predicting the risk of difficult airway management. Ratio of height to sternomental distance is a new test for predicting difficult laryngoscopy. Analytical cross - sectional study. Guilan University of Medical Sciences, Rash-lran. 1[st] Oct, 2009 to 30[th] Dec, 2010. 470 consecutive patients scheduled for elective surgery undergoing general anesthesia and requiring endotracheal intubation. The tests that were used to predict difficult laryngoscopy included: mouth opening range, body mass index [BMl], thyromental distance, sternomental distance, and neck movement range, ratio of height to thyromental distance, ratio of height to sternomental distance [RHSMD] and assessment of oropharyngeal view by modified Mallampati classification. After general anesthesia, glottic visualization was assessed during laryngoscopy using Cormack and Lehane classification. Multivariate analysis and 95 percent confidence interval with SPSS 14 statistical package were used to compare the results of study. Neck movement range /= 12.5 were valuable respectively. Odds ratio [95 percent confidence interval] of the neck movement range /= 12.5 and RHTIVID >/= 23.5 were 17.7[9.57 - 49.76], 12.28 [7.6 - 47.04], 12.22 [22.8-76.6], 9.35 [2.29 -10.52], 5.6 [0.08 - 0.89], 3.78 [0.022 - 0.595] respectively. RHSMD had the least false negative value. Cut off point of RHSMD >/= 12.5 and RHTMD >/= 23.5 was not different between men and women. RHSMD is a useful and valuable clinical screening test for predicting difficult laryngoscopy.
ABSTRACT
Preoperative evaluation of anatomical landmarks and clinical factors helps to identify potentially difficult laryngoscopies; however, its predictive reliability is unclear. As the ratio of height to thyromental distance [RHTMD] is a newer upper airway predictive test for difficult laryngoscopy, the predictive value and odds ratios of RHTMD versus mouth opening, thyromental distance[TMD], neck movement, and oropharyngeal view [modified Mallampati] were evaluated. Data of 407 consecutive patients scheduled for elective surgery with general anesthesia requiring endotracheal intubation were collected and all five factors were assessed before surgery. Four senior anesthesiology residents, not aware of the recorded preoperative airway assessment, performed the laryngoscopy and grading [as in Cormack and Lehane's classification]. Difficult laryngoscopy [Grade 3 or 4] occurred in 94 patients [23.1%]. In the multivariate analysis, three criteria were found independent for difficult laryngoscopy [neck movement /= 24]. Neck movement [NM] /= 24 were valuable with lowest NPV. The multivariate analysis Odds ratio [95% confidence interval] of the NM, Mallampati class, IIG and RHTMD were 18.16 [9.634 - 34.265], 12.498 [6.744 - 23.16], 11.183 [6.571 - 19.03] and 3.123 [1.933 - 5.047] respectively.TMD