Table 3.
The ultrasonography indicators and main result extracted for predict of difficult intubation
| Indicators list in study | Presented in | Main result (Mean difference, accuracy, and other results) | |
|---|---|---|---|
| Distance from skin to epiglottis | Skin to epiglottis distance (cm) | Daggupati, H.; 2020 | Mean (95% CI): In Diff = 2.17 (2.12–2.22) vs Easy = 1.68 (1.65–1.70); P-value< 0.001 |
| Neck soft tissue from skin to epiglottis (DSE) (cm) | Martínez-García, A.;2020 |
Mean (SD): In Diff = 2.90 (0.46) vs Easy = 2.32 (0.54); P-value = 0.001 AUC = 0.79 (95%CI: 0.62–0.89), P = 0.001; In cut-off = UK: Sensitivity =93.75%، Specificity =50.11%، PPV =46.88%، NPV =94.44% In cut-off = 3: Sensitivity = 56.3% (95% CI: 28.8–83.7), Specificity = 88.2% (95% CI: 75.9–100), PPV = 69.2% (95% CI: 40.3–98.2), NPV = 81.1% (95% CI: 67.1–95.1) |
|
| Distance from skin to epiglottis (DSEM) | Koundal, V.;2019 |
Mean (SD): In CL1 = 1.42 (0.33), CL2 = 1.46 (0.36), CL3 = 1.89 (0.36), CL4 = 1.96 (0.21); P-value< 0.001 AUC = 0.819 (95%CI: 0.758–0.880), In cut-off = 1.615: Sensitivity = 89.7%, Specificity = 64.8%, PPV = 50.98%, NPV = 93.88% |
|
| Pre-epiglottic Soft tissue thickness (mm) | Petrișor, C.; 2018 | Mean (SD): In Diff = 15.75 (30.73) vs Easy = 17.39 (15.15); P-value = 0.6 | |
| Distance from skin to epiglottis (DSE) (mm) | Pinto, J.; 2016 | Mean (SD): In Diff = 28.25 (4.43) vs Easy = 23.32 (3.86); P-value = 0.000 | |
| At thyrohyoid membrane level, the distance from skin to epiglottis midway (DSEM) (cm) | Wu, J.; 2014 |
Mean (SD): In Diff = 2.39 (0.34) vs Easy = 1.49 (0.39); P-value< 0.001 AUC = 0.90 (95% CI: 0.85–0.94); P-value< 0.001 |
|
| mDSE (median distance from skin to epiglottis), (cm) | Falcetta, S.; 2018 | AUC = 0.906 (95% CI: 0.86–0.93), In cut-off = 2.54: Sensitivity = 82.0%, Specificity = 91.0% | |
| Skin to epiglottis | Parameswari, A.; 2017 | In cut-off = UK: Sensitivity = 75.0%, Specificity = 63.6%, PPV = 17.5, NPV = 96.2 | |
| Thickness of anterior neck soft tissue at Vocal cords | Anterior neck thicknesses at the Vocal cords | Fulkerson, J.S.;2019 | Mean (SD): In Diff = 0.73 (0.15) vs Easy = 0.70 (0.23); P-value = 0.631 |
| Distance from skin to glottis | Martínez-García, A.;2020 |
Mean (SD): In Diff = 1.05 (0.25) vs Easy = 1.07 (0.33); P-value = 0.749 AUC = 0.47 (95%CI: 0.31–0.64), P = 0.755; In cut-off = UK: Sensitivity =81.25%، Specificity =23.53%، PPV =33.33%، NPV =72.73% |
|
| Thickness of anterior neck soft tissue at Vocal cords | Adhikari, S.; 2011 | No-significant difference in Diff and Easy | |
| Neck soft tissue, from the skin to the anterior aspect of the trachea at the vocal cords anterior to the thyroid cartilage | Komatsu, R.; 2007 |
Mean (SD): In Diff = 20.4 (3.0) vs Easy = 22.3 (3.8); P-value = 0.049 OR = 0.16 (0.02–1.75); P-value = 0.134 |
|
| Distance from the skin to the anterior aspect of the trachea was measured at vocal cords (zone 1) | Yilmaz, C.; 2018 |
Mean (SD): In Diff = 1.21 (0.28) vs Easy = 1.32 (0.30); P-value = 0.260 OR = 0.204 (95% CI: 0.006–7.34; P-value = 0.385 |
|
| At anterior commissure level, the minimal distance from skin to anterior commissure (DSAC) | Wu, J.; 2014 |
Mean (SD): In Diff = 1.30 (0.31) vs Easy = 0.92 (0.20); P-value< 0.001 AUC = 0.85 (95% CI: 0.79–0.89); P-value< 0.001 |
|
| The distance from the skin to the anterior aspect of the trachea was measured at vocal cords (zone 1) | Ezri, T.; 2003 | Mean (SD): In Diff 28.0 (2.7) vs Easy 17.5 (1.8); P-value< 0.001 | |
| mVC (the median distance from the skin to the apex of the vocal cords), | Falcetta, S.; 2018 | AUC = 0.54 (95% CI:0.48–0.60), Sensitivity =53, Specificity =66 | |
| Anterior neck soft tissue thickness at the level of the vocal cords (ANS-VC) | Reddy, P.B.; 2016 | Mean (SD): In CL1 = 0.25 (0.11), Range = 0.11–0.53/ CL2 = 0.25 (0.12), Range = 0.07–0.67/ CL3 = 0.35 (0.18), Range = 0.18–0.76; P-value = 0.014 | |
| Anterior neck soft tissue at the of the hyoid bone | Neck soft tissue from skin to hyoid (DSH) (cm) | Martínez-García, A.;2020 |
Mean (SD): In Diff = 1.35 (0.21) vs Easy = 1.30 (0.31); P-value = 0.580 AUC = 0.57 (95%CI: 0.40–0.73); P < 0.001; In cut-off = UK: Sensitivity =75.01%، Specificity =41.18%، PPV =37.5%، NPV =77.78% |
| Anterior neck thicknesses at the hyoid Bone (HB) (cm) | Fulkerson, J.S.;2019 | Mean (SD): In Diff = 0.93 (0.22) vs Easy = 0.97 (0.31); P-value = 0.681 | |
| Thickness of anterior soft tissue neck at the level of hyoid bone (DSHB) | Koundal, V.;2019 |
Mean (SD): In CL1 = 0.84 (0.16), CL2 = 0.85 (0.17), CL3 = 0.98 (0.23), CL4 = 1.15 (0.18); P-value< 0.001 AUC = 0.680 (95%CI: 0.594–0.767), In cut-off = 0.99: Sensitivity = 48.0%, Specificity = 82.0%, PPV = 52.83%, NPV = 79.59% |
|
| Distance from skin to hyoid bone (SHB) in neutral | Yadav, N.K.;2019 |
Mean (SD): In Diff = 0.74 (0.23) vs Easy = 0.56 (0.19); P-value = 0.001 AUC = 0.72 (95%CI: 0.61–0.82), In cut-off = 0.66: Sensitivity = 68.0%, Specificity = 69.0% |
|
| Anterior neck soft tissue at the of the hyoid bone | Adhikari, S.; 2011 | Mean (CI 95%): In Diff = 1.69 cm (1.19–2.19) vs Easy = 1.37 (1.27–1.46); P-value< 0.05 | |
| At hyoid bone level, the minimal distance from the hyoid bone to skin surface (DSHB) (cm) | Wu, J.; 2014 |
Mean (SD): In Diff = 1.51 (0.27) vs Easy = 0.98 (0.26); P-value< 0.001 AUC = 0.92 (95%CI: 0.87–0.95); P < 0.001 |
|
| Skin to hyoid distance | Parameswari, A.; 2017 | In cut-off = UK: Sensitivity = 58.3%, Specificity = 56.8%, PPV = 12.1, NPV = 93.1 | |
| Anterior neck soft tissue thickness at the level of the hyoid (ANS-Hyoid) | Reddy, P.B.; 2016 | Mean (SD): In CL1 = 0.36 (0.20), Range = 0.12–0.98/ CL2 = 0.35 (0.14), Range = 0.15–0.69/ CL3 = 0.38 (0.16), Range = 0.18–0.68; P-value = 0.857 | |
| Hyomental distance (HMD) with neck extended | HMD distance between the hyoid bone and the posterior border of the symphisis menti: maximum hyperextended | Petrișor, C.; 2018 | Mean (SD): In Diff 4.9 (0.22) vs Easy 5.8 (0.42); P-value = 0.1 |
| Hyomental distance (HMD) with neck extended (cm) | Fulkerson, J.S.;2019 | Mean (SD): In Diff = 5.10 (0.65) vs Easy = 5.28 (0.69); P-value = 0.341 | |
| Mentohyoid distance | Daggupati, H.; 2020 | Mean (95% CI): In Diff = 3.70 (3.5–3.9) vs Easy = 4.72 (4.63–4.90); P-value = 0.341 | |
| Hyomental distance ratio | Hyomental distance ratio (HMDR) (cm) | Koundal, V.;2019 |
Mean (SD): In CL1 = 1.12 (0.03), CL2 = 1.11 (0.03), CL3 = 1.09 (0.01), CL4 = 1.04 (0.02); P-value< 0.001 AUC = 0.762 (95%CI: 0.686–0.838), In cut-off = 1.087: Sensitivity = 65.0%, Specificity = 77.0%, PPV = 54.29%, NPV = 84.62% |
| HMDR (the ratio between the HMD in the maximum hyperextended position to that in the neutral position) | Petrișor, C.; 2018 | Mean (SD): In Diff 1.21 (0.0005) vs Easy 1.34 (0.1); P-value = 0.0002 | |
| Hyomental distance ratio (HMDR) (cm) | Wojtczak, J.A.; 2011 | Mean (SD): In Diff 1.02 (0.02) vs Easy 1.14 (0.02); P-value< 0.001 | |
| Hyomental distance ratio (HMDR), cm | Rana, S.; 2018 |
Mean (SD): In CL1 = 1.11 (0.35), CL2 = 1.12 (0.29), CL3 = 1.07 (0.39), CL4 = 1.04 (0.01); P-value< 0.001 AUC = 0.871, In cut-off = 1.085: Sensitivity = 75.0%, Specificity = 85.3%, PPV = 65.6%, NPV = 90.1% |
|
| Hyomental distance ratio (HMDR) (cm) | Andruszkiewicz, P.; 2016 |
Mean (SD): In Diff = 1.07 (0.08) vs Easy = 1.12 (0.07); P-value = 0.0022 AUC = 0.710, P-value = 0.0036; In cut-off = UK: Sensitivity = 42.9%, Specificity = 96.0%, PPV = 56.2%, NPV = 93.4%; |
|
| Pre-E/EVC | Pre-E/E-VC | Koundal, V.;2019 |
Mean (SD): In CL1 = 1.22 (0.44), CL2 = 0.56 (0.27), CL3 = 1.91 (0.25), CL4 = 2.25 (0.31); P-value< 0.001 AUC = 0.871 (95%CI: 0.820–0.923), In cut-off = 1.875: Sensitivity = 82.8%, Specificity = 83.8%, PPV = 67.61%, NPV = 92.25% |
| Pre-E/EVC (depth of the pre-epiglottic space/ the distance from the epiglottis to the midpoint of the distance between the vocal cords) | Rana, S.; 2018 |
Mean (SD): In CL1 = 1.33 (0.335), CL2 = 1.62 (0.264), CL3 = 1.87 (0.243), CL4 = 2.22 (0.29); P-value< 0.001 AUC = 0.868, In cut-off = 1.77: Sensitivity = 82.0%, Specificity = 80.0%, PPV = 60.5%, NPV = 92.3% |
|
| Pre-E/E-VC | Reddy, P.B.; 2016 | Mean (SD): In CL1 = 1.09 (0.38), Range = 0.41–2.22/ CL2 = 1.28 (0.37), Range = 0.58–2.02/ CL3 = 1.29 (0.44), Range = 0.76–2.46; P-value = 0.044 | |
| Ratio of Pre-Epiglottis space and Epiglottis-to-Vocal cords distances (Pre-E/E-VC) | Gupta, D.; 2013 | Mean (SD): In CL1 = 0.89 (0.61), CL2 = 1.65 (0.81), CL3 = 2.54 (0.98), CL4 = No data yet, P-value = UK | |
| Anterior neck soft tissue at thyroid isthmus | Thickness of anterior neck soft tissue at thyroid isthmus | Adhikari, S.; 2011 | No-significant difference in Diff and Easy |
| Distance from the skin to the anterior aspect of the trachea was measured thyroid isthmus | Yilmaz, C.; 2018 |
Mean (SD): In Diff = 1.55 (0.32) vs Easy = 1.78 (0.39); P-value = 0.130 OR = 0.144 (95% CI: 0.008–2.56); P-value = 0.187 |
|
| The distance from the skin to the anterior aspect of the trachea was measured at thyroid isthmus (zone 2) | Ezri, T.; 2003 | Mean (SD): In Diff = 25.0 (1.3) vs Easy = 22.8 (5.0); P-value = 0.16 | |
| Anterior neck soft tissue at suprasternal notch | Thickness of anterior neck soft tissue at Suprasternal notch | Adhikari, S.; 2011 | No-significant difference in Diff and Easy |
| Distance from the skin to the anterior aspect of the trachea was measured at suprasternal notch (zone 3) | Yilmaz, C.; 2018 |
Mean (SD): In Diff = 2.26 (0.55) vs Easy = 2.32 (0.52); P-value = 0.875 OR = 0.924 (95% CI: 0.15–5.56); P-value = 0.931 |
|
| The distance from the skin to the anterior aspect of the trachea was measured at suprasternal notch (zone 3) | Ezri, T.; 2003 | Mean (SD): In Diff = 33.0 (4.3) vs Easy = 27.4 (6.6); P-value = 0.013 | |
| Tongue volume | Tongue volume (cm3) | Wojtczak, J.A.; 2011 | Mean (SD): In Diff = 137.67 (29.28) vs Easy = 168.33 (34.22); P-value = 0.126 |
| Volume of tongue, cm3 | Parameswari, A.; 2017 | In cut-off = 100: Sensitivity = 66.7%, Specificity = 62.7%, PPV = 15.4%, NPV = 94.6% | |
| Tongue volume | Andruszkiewicz, P.; 2016 |
Mean (SD): In Diff = 121.7 (27.1) vs Easy = 111.2 (22.1); P-value = 0.0415 AUC = 0.626, P-value = 0.0456; In cut-off = UK: Sensitivity = 9.1%, Specificity = 97.7%, PPV = 33.3%, NPV = 89.6%; |
|
| Floor of the mouth muscle volumes | Floor of the mouth muscle volumes (MVFM, muscle volume of the floor of the mouth (cm3)) | Wojtczak, J.A.; 2011 | Mean (SD): In Diff = 34.87 (11.95) vs Easy = 37.72 (13.17); P-value = 0.703 |
| Volume of floor of mouth | Parameswari, A.; 2017 | In cut-off = UK: Sensitivity = 50.0%, Specificity = 55.9%, PPV = 10.3, NPV = 91.7 | |
| floor of the mouth muscle volume (FMMV) (cm3) | Andruszkiewicz, P.; 2016 |
Mean (SD): In Diff = 20.10 (5.39) vs Easy = 19.32 (4.15); P-value = 0.4224 AUC = 0.559, P-value = 0.421; In cut-off = UK: Sensitivity = 31.7%, Specificity = 71.8%, PPV = 12.3%, NPV = 89.4% |
|
| Hyomental distance in the head positions | Hyomental distance in the head positions (HMDE) (mm) | Wojtczak, J.A.; 2011 | Mean (SD): In Diff = 52.65 (5.89) vs Easy = 65.65 (4.17); P-value = 0.001 |
| hyomental distance in extension positions (HMDE) (cm) | Andruszkiewicz, P.; 2016 |
Mean (SD): In Diff = 4.28 (0.64) vs Easy = 4.82 (0.46); P-value = 0.0009 AUC = 0.758, P-value< 0.0001; In cut-off = UK: Sensitivity = 38.1%, Specificity = 97.7%, PPV = 66.7%, NPV = 93.0% |
|
| Hyomental distance in the neutral positions | Hyomental distance in the neutral positions (HMDN) | Wojtczak, J.A.; 2011 | Mean (SD): In Diff = 51.33 (5.36) vs Easy = 57.55 (4.36); P-value = 0.052 |
| Hyomental distance in neutral positions HMDN (cm), | Andruszkiewicz, P.; 2016 |
Mean (SD): In Diff = 3.99 (0.56) vs Easy = 4.32 (0.42); P-value = 0.0014 AUC = 0.660, P-value = 0.002; In cut-off = UK: Sensitivity = 28.6%, Specificity = 94.4%, PPV = 37.5%, NPV = 91.8% |
|
| Length of the thyrohyoid membrane | Length of the thyrohyoid membrane | Wang, L.;2019 |
Mean (SD): In Diff = 1.83 (0.07) vs Easy = 2.07 (0.03); P-value< 0.001 Odds ratio (OR) = 0.22 (95% CI: 0.09–0.51) |
| Thyrohyoid distance | Abraham, S.; 2018 | Mean (SD): In Diff = 1.62 (0.44) vs Easy = 1.71 (0.62); P-value = 0.563 | |
| Tongue thickness | Tongue thickness (TT) (mm) | Xu, L.;2019 |
Mean (SD): In Diff = 61.4 (2.8) vs Easy = 54.6 (3.5); P-value< 0.001 AUC = 0.93 (95%CI: 0.88–0.98); In cut-off > 58.65 mm: Sensitivity = 0.85 (95% CI: 0.73–0.97), Specificity = 0.91 (95% CI: 0.85–0.98), PPV = 0.83 (95% CI: 0.71–0.98), NPV = 0.92 (95% CI: 0.86–0.98) |
| Tongue thickness | Yadav, N.K.;2019 |
Median (IQR): In Diff = 6.1 (1.04) vs Easy = 5.30 (1.02); P-value = 0.001 AUC = 0.72 (95%CI: 0.62–0.81), In cut-off = UK: Sensitivity = 71.0%, Specificity = 72.0% |
|
| Tongue thickness (cm) | Yao, W.; 2017 (a) |
Mean (SD): In Diff = 6.4 (0.4) vs Easy = 5.9 (0.5); P-value< 0.001 AUC = 0.78 (95%CI: 0.77–0.80); In cut-off > 6.1 cm: Sensitivity = 0.75 (95% CI: 0.60–0.86), Specificity = 0.72 (95% CI: 0.70–0.74), PPV = 0.06 (95% CI: 0.04–0.08), NPV = 0.99 (95% CI: 0.99–1.0) Odds ratio (OR) in cut-off = 7.7 (95%CI: 3.9–16) |
|
| Condylar translation | Condylar translation (CT) (mm) | Xu, L.;2019 |
Mean (SD): In Diff = 10.5 (2.0) vs Easy = 12.8 (2.5); P-value< 0.001 AUC = 0.77 (95%CI: 0.67–0.86); In cut-off < 11.05 mm: Sensitivity = 0.70 (95% CI: 0.55–0.89), Specificity = 0.81 (95% CI: 0.72–0.90), PPV = 0.65 (95% CI: 0.50–0.80), NPV = 0.84 (95% CI: 0.76–0.93) |
| Mandibular condylar mobility (mm) | Yao, W.; 2017 (b) |
Mean (SD): In Diff = 9.2 (1.7) vs Easy = 13.7 (2.5); P-value< 0.001 In Cut-off limited condylar translation: Sensitivity = 0.81 (99% CI: 0.6–0.95), Specificity = 0.91 (99% CI: 0.87–0.94), PPV = 0.45 (99% CI: 0.29–0.62), NPV = 0.98 (99% CI: 0.96–1) Odds ratio (OR) in limited condylar translation = 40.4 (CI:13.5–121.4) |
|
| Anterior neck soft tissue at the of the Thyrohyoid membrane | Anterior neck soft tissue at the of the Thyrohyoid membrane | Adhikari, S.; 2011 | Mean (95% CI): In Diff = 3.47 (2.88–4.07) vs Easy = 2.37 (2.29–2.44); P-value< 0.05 |
| Anterior neck thicknesses at the Thyrohyoid Membrane (THM) | Fulkerson, J.S.;2019 | Mean (SD): In Diff = 2.0 (0.47) vs Easy = 2.14 (0.48); P-value = 0.304 | |
| Distance from skin to the thyrohyoid membrane (STM) in neutral | Yadav, N.K.;2019 |
Mean (SD): In Diff = 1.58 (0.34) vs Easy = 1.93 (0.42); P-value< 0.001 AUC = 0.73 (95%CI: 0.63–0.83), In cut-off = 2.03: Sensitivity = 65.0%, Specificity = 69.0% |
|
| HMD distance between the hyoid bone and the posterior border of the symphisis menti | HMD distance between the hyoid bone and the posterior border of the symphisis menti: neutral | Petrișor, C.; 2018 | Mean (SD): In Diff 4.04 (0.1) vs Easy 4.34 (0.32); P-value = 0.31 |
| HMD distance between the hyoid bone and the posterior border of the symphisis menti: ramped | Petrișor, C.; 2018 | Mean (SD): In Diff 4.53 (0.1) vs Easy 5.17 (0.28); P-value = 0.03 | |
| HMDR (the ratio between the HMD in the ramped position to that in neutral position) | Petrișor, C.; 2018 | Mean (SD): In Diff 1.12 (0.001) vs Easy 1.2 (0.1); P-value = 0.02 | |
| Other indicators | |||
| 1 | Ratios of tongue thickness to thyromental distance | Yao, W.; 2017 (a) |
Mean (SD): In Diff = 0.94 (0.10) vs Easy = 0.80 (0.11); P-value< 0.001 AUC = 0.86 (95% CI: 0.84–0.87); In cut-off > 0.87: Sensitivity = 0.84 (95% CI: 0.71–0.93), Specificity = 0.79 (95% CI: 0.77–0.81), PPV = 0.09 (95% CI: 0.06–0.11), NPV = 1.0 (95% CI: 0.99–1.0) Odds ratio (OR) in cut-off = 20 (95% CI: 9.6–44.0) |
| 2 | Tongue cross-sectional area (TCSA) (cm2) | Andruszkiewicz, P.; 2016 |
Mean (SD): In Diff = 23.1 (3.57) vs Easy = 21.6 (3.09); P-value = 0.033 AUC = 0.622, P-value = 0.037; In cut-off = UK: Sensitivity = 9.1%, Specificity = 97.2%, PPV = 28.6%, NPV = 94.5% |
| 3 | Width of the tongue (cm) | Wang, L.;2019 | Mean (SD): In Diff = 3.02 (0.05) vs Easy = 2.81 (0.03); P-value< 0.001 |
| 4 | DSH + DSE | Martínez-García, A.;2020 |
Mean (SD): In Diff = 4.25 (0.45) vs Easy = 3.62 (0.77); P-value = 0.001 AUC = 0.75 (95%CI: 0.62–0.89), P = 0.001; In cut-off = UK: Sensitivity =81.25%، Specificity =70.59%، PPV =56.52%، NPV =88.89% In cut-off = 4.5: Sensitivity = 37.5% (95% CI: 10.7–64.4), Specificity = 82.4% (95% CI: 68.1–96.6), PPV = 50.0% (95% CI: 17.5–82.5), NPV = 73.7% (95% CI: 58.2–89.0) |
| 5 | DSE – DSG | Martínez-García, A.;2020 |
Mean (SD): In Diff = 1.83 (0.54) vs Easy = 1.24 (0.46); P-value = 0.001 AUC = 0.82 (95%CI: 0.68–0.96), P = 0.001; In cut-off = UK: Sensitivity =81.25%، Specificity =52.94%، PPV =44.83%، NPV =85.71% In cut-off = 1.9: Sensitivity = 68.8% (95% CI: 42.9–94.6), Specificity = 91.2% (95% CI: 80.2–100), PPV = 78.6% (95% CI: 53.5–100), NPV = 86.1% (95% CI: 73.4–98.8) |
| 6 | Thickness of the base of the tongue | Wang, L.;2019 |
Mean (SD): In Diff = 2.85 (0.09) vs Easy = 2.56 (0.04); P-value = 0.002 Odds ratio (OR) = 2.51 (95% CI: 1.38–4.55) |
| 7 | Angle between the epiglottis and glottis (°) | Wang, L.; 2019 |
Mean (SD): In Diff = 54.97 (4.93) vs Easy = 47.49 (4.17); P-value< 0.001 Odds ratio (OR) = 0.62 (95% CI: 0.54–0.71) AUC = 0.902 (95%CI: 0.846–0.957), In cut-off = 50°: Sensitivity = 81.0%, Specificity = 89.0 |
| 8 | Distance from skin to hyoid bone (SHB) in sniffing | Yadav, N.K.; 2019 |
Mean (SD): In Diff = 0.53 (0.20) vs Easy = 0.73 (0.23); P-value< 0.001 AUC = 0.73 (95%CI: 0.63–0.84), In cut-off = 0.77: Sensitivity = 68.0%, Specificity = 72.0% |
| 9 | Distance from skin to the thyrohyoid membrane (STM) in sniffing | Yadav, N.K.; 2019 |
Mean (SD): In Diff = 1.54 (0.35) vs Easy = 1.84 (0.39); P-value< 0.001 AUC = 0.70 (95%CI: 0.60–0.81), In cut-off = 1.9: Sensitivity = 65.0%, Specificity = 63.0% |
| 10 | Tongue width (TW) (cm) | Andruszkiewicz, P.; 2016 |
Mean (SD): In Diff = 5.21 (0.45) vs Easy = 5.14 (0.46); P-value = 0.485 AUC = 0.589, P-value = 0.483; In cut-off = UK: Sensitivity = 9.1%, Specificity = 76.3%, PPV = 4.5%, NPV = 87.1% |
| 11 | Tongue thickness-to-oral cavity height ratio (TT/OCH) | Andruszkiewicz, P.; 2016 |
Mean (SD): In Diff = 0.84 (0.04) vs Easy = 0.83 (0.04); P-value = 0.347 AUC = 0.513, P-value = 0.339; In cut-off = UK: Sensitivity = 31.8%, Specificity = 68.4%, PPV = 11.1%, NPV = 89.0% |
| 12 | Floor of the mouth muscle Cross-sectional area (FFM CSA) (cm2) | Andruszkiewicz, P.; 2016 |
Mean (SD): In Diff = 4.75 (1.04) vs Easy = 4.48 (0.80); P-value = 0.1464 AUC = 0.571, P-value = 0.148 In cut-off = UK: Sensitivity = 9.1%, Specificity = 93.8%, PPV = 15.4%, NPV = 89.2% |
| 13 | Ratio of the Depth of the pre-epiglottic space (Pre-E) to the distance (cm) | Reddy, P.B.; 2016 | Mean (SD): In CL1 = 0.98 (0.25), Range = 0.43–0.74/ CL2 = 1.08 (0.21), Range = 0.59–1.66/ CL3 = 1.04 (0.22), Range = 0.59–1.4; P-value = 0.134 |
| 14 | Distance from the epiglottis to the mid-point of the distance between the vocal cords (E-VC) (cm) | Reddy, P.B.; 2016 | Mean (SD): In CL1 = 0.96 (0.30), Range = 0.42–1.72/ CL2 = 0.89 (0.23), Range = 0.57–1.58/ CL3 = 0.84 (0.19), Range = 0.57–1.25; P-value = 0.214 |
| 15 | Hyomental distance (HMD) to Hyoid bone (HB) ratio | Fulkerson, J.S.;2019 | Mean (SD): In Diff = 5.05 (1.73) vs Easy = 6.12 (2.7); P-value = 0.139 |
| 16 | Hyomental distance to Thyrohyoid membrane (THM) ratio | Fulkerson, J.S.;2019 | Mean (SD): In Diff = 2.55 (1.03) vs Easy = 2.62 (0.85); P-value = 0.749 |
| 17 | Hyomental distance to vocal cords (VC) ratio | Fulkerson, J.S.;2019 | Mean (SD): In Diff = 6.87 (2.62) vs Easy = 8.25 (2.92); P-value = 0.080 |
| 18 | Hyomental distance to Thyrohyoid membrane (THM) ratio | Fulkerson, J.S.;2019 | Mean (SD): In Diff = 0.49 (0.14) vs Easy = 0.47 (0.17); P-value = 0.606 |
| 19 | Hyoid bone to vocal cords ratio | Fulkerson, J.S.;2019 | Mean (SD): In Diff = 1.37 (0.46) vs Easy = 1.47 (0.59); P-value = 0.482 |
| 20 | Thyrohyoid membrane to vocal cords ratio | Fulkerson, J.S.;2019 | Mean (SD): In Diff = 2.85 (0.82) vs Easy = 3.3 (1.24); P-value = 0.174 |
| 21 | Thickness of the lateral pharyngeal | Wang, L.; 2019 |
Mean (SD): In Diff = 0.91 (0.04) vs Easy = 0.94 (0.02); P-value = 0.432 Odds ratio (OR) = 2.51 (95% CI: 1.38–4.55) |
| 22 | Thickness of submental region | Abraham, S.; 2018 | Mean (SD): In Diff = 1.31 (0.27) vs Easy = 1.11 (0.32); P-value = 0.057 |
| 23 | Epiglottis to hyoid bone distance | Abraham, S.; 2018 | Mean (SD): In Diff = 1.87 (0.36) vs Easy = 1.8 (0.54); P-value = 0.695 |
| 24 | Skin pad thickness to thyroid cartilage | Abraham, S.; 2018 | Mean (SD): In Diff = 1.29 (0.48) vs Easy = 1.08 (0.49); P-value = 0.191 |
| 25 | Ratio of the pre-epiglottis space distance and the distance between epiglottis and vocal folds (Pre-E/aVF) | Chan, S.M.M.; 2018 | AUC = 0.648, P-value = 0.044; In cut-off > 1: Sensitivity = 79.5%, Specificity = 39.2%, PPV = 40.8%, NPV = 78.4%, PLR = 1.31, NLR = 0.52; |
| 26 | Pre-epiglottic area (PEA), cm2 | Falcetta, S.; 2018 | AUC = 0.93 (95% CI: 0.89–0.95); In cut-off = 5.04: Sensitivity = 85%, Specificity = 88% |
| 27 | Ability to view the hyoid bone in sublingual ultrasound | Hui, C.M.; 2014 |
Number (%): In Dif.: not seen = 8 (72.7), seen = 3 (27.3) vs Easy: not seen = 3 (3.4), seen = 86 (96.6); P-value< 0.001 Sensitivity = 70.0%, Specificity = 97.0%, PLR = 21.6, NLR = 0.28 |
| 28 | Base of the tongue | Adhikari, S.; 2011 | No-significant difference |
AUC Area under the curve of ROC, BMI Body mass index, CL Cormack-Lehane grade, CI Confidence interval, Diff Difficult intubation group, F Female, M male, NPV Negative predictive value, NLR Negative likelihood ratio, OR Odds ratio, PPV Positive predictive value, PLR Positive likelihood, SD Standard deviation, UK Un-Known