Fig. 2

Decision tree for the prediction of tracheostomy. At each split, a patient goes to the left branch when the left-side condition is satisfied and goes to the right branch when the right-side condition is satisfied. The top number (numerator) is the number of patients who received a tracheostomy. The bottom number (denominator) is the sample size for that group. Assessing 2 and 3 results in odds ratio 2.14 with 95% CI 1.03–4.52 and p value = 0.034, 50% sensitivity, and 68% specificity. Assessing 4 and 5 results in odds ratio 3.35 with 95% CI 0.61–35.0 and p value = 0.178; sensitivity improves to 54% and specificity to 76%. Finally, assessing 6 and 7 results in odds ratio 2.33 with 95% CI 0.54–12.1 and p value = 0.225; combining three classification criteria, the sensitivity is 63% and the specificity is 84%