Abstract Background and objectives Several anthropometric measurements have been suggested to identify a potentially difficult airway. We studied thyromental height (TMH) as a predictor of difficult laryngoscopy and difficult intubation. We also compared TMH, ratio of height to thyromental distance (RHTMD), and thyromental distance (TMD) as predictors of difficult airway. Methods This cross-sectional observational study was conducted in 300 adult surgical patients requiring tracheal intubation. Preoperatively airway characteristics were assessed. Standard anesthesia was administered. Degree of difficulty with mask ventilation, laryngoscopic view, duration of laryngoscopy, and difficulty in tracheal intubation (intubation difficulty scale score) were noted. Multivariate logistics regression analysis was performed to identify independent predictors for difficult laryngoscopy. Results Laryngoscopy was difficult in 46 of 300 (15.3%) patients; all 46 patients had Cormack-Lehane grade 3 view. Duration of laryngoscopy was 27 ± 11 s in patients with difficult laryngoscopy and 12.7 ± 3.9 s in easy laryngoscopy; p= 0.001. Multivariate analysis identified that TMH, presence of short neck, and history of snoring were independently associated with difficult laryngoscopy. Incidence of difficult intubation was 17.0%. A shorter TMH was associated with higher IDS scores; r = -0.16, p= 0.001. TMH and duration of laryngoscopy were found to be negatively correlated; a shorter TMH was associated with a longer duration of laryngoscopy; r = -0.13, p= 0.03. The cut-off threshold value for TMH in our study is 4.4 cm with a sensitivity of 66% and a specificity of 54%. Conclusion Thyromental height predicts difficult laryngoscopy and difficult intubation. TMD and RHTMD did not prove to be useful as predictors of difficult airway.

Este estudio utiliza datos de la Encuesta Nacional de Salud Familiar (International Institute for Population Sciences 1995) realizada en el estado de Tamil Nadu, India. Se desarrollaron modelos de Cox para analizar el efecto de la lactancia materna cuando varía en el tiempo y el factor tiempo depende de los intervalos genésicos. La lactancia materna sólo mejora la probabilidad de acceder a un nivel más alto en cada intervalo de nacimiento. Otros factores que entraron en los modelos fueron en el intervalo del primer parto: nivel educativo de la madre (secundaria y superior) y trabajo de la madre; en el intervalo del segundo parto: nivel de supervivencia en el índice de vida infantil y nivel educativo del padre (secundaria y superior), y en el intervalo del tercer parto: lactancia materna más 22 meses. Cada uno de los anteriores es un factor protector para ampliar el intervalo entre nacimientos en el estudio. Además, este estudio confirma los modelos desarrollados en los servicios públicos de predicción para los intervalos genésicos.

The present study uses data from National Family Health Survey (NFHS-1) 1992-93 (International Institute for Population Sciences 1995) conducted in the state of Tamil Nadu, India. Cox models were developed to analyze the effect of breastfeeding as time varying and time dependent factor on birth intervals. Breastfeeding alone improved the log likelihood up to a higher level in each birth interval. Other factors that entered into the models were: at first birth interval, womens education (high school & above) and working status of women; at second birth interval, survival status of index child alive and husbands education (high school & above), and at third birth interval, breastfeeding more than 22 month were found to be protective factors for next births. Validation of the developed models was done through bootstrapping to predict birth intervals.