Background
Methods
Search strategy
Selection of studies and data extraction
Statistical analysis
Results
Screening and article selection
Characteristics of the included studies
First Author; Year | Country | Study design | Sample size | Participants | Demographic characteristics | Difficult intubation (%) | ||
---|---|---|---|---|---|---|---|---|
Age | Sex (%) | BMI | ||||||
Daggupati, H.; 2020 [7] | India | Prospective observational study | 310 | Patients posted for elective surgery planned under general anaesthesia with tracheal intubation using Macintosh laryngoscope | Mean (SD) = 33.0 (13.0) | M: 185 (59.7), F: 125 (40.3) | Mean (SD): 25.5 (2.1) | 78 (25.0) |
Martínez-García, A.;2020 [8] | Spain | Prospective observational study | 50 | Adult patients, and ASA grade one to four, scheduled for surgery requiring general anesthesia with orotracheal intubation after classical laryngoscopy | Mean (SD) in Diff: 64.0 (11.0) vs Easy 52.0 (14.0) | M: 24 (48.0), F: 26 (52.0) | Mean (SD): Diff: 30.1 (3.5) vs Easy 30.0 (7.0) | 16 (32.0) |
Fulkerson, J.S.;2019 [9] | USA | Cross-sectional, study | 144 | Veterans ages 19–79 scheduled for elective surgical procedures | Range = 29–78; Mean (SD) = 60.0 [10] | M: 130 (90.3), F: 14 (9.7) | Range = 17–46; Mean = 30.0 | 15 (10.4) |
Koundal, V.;2019 [11] | India | Prospective observational study | 200 | Patients requiring general anaesthesia and tracheal intubation | Mean = 43.2 | M: 105 (52.5), F: 95 (47.5) | Mean = 22.2 | 29 (14.3) |
Wang, L.;2019 [12] | China | UK | 508 | Patients undergoing elective surgery under general anesthesia with tracheal intubation | Mean = 52.3 | UK | Mean (SD) in Diff: 24.7 (0.49) vs Easy 23.5 (0.22) | 47 (9.3) |
Xu, L.;2019 [10] | China | UK | 119 | Parturients undergoing elective cesarean delivery | Mean in Diff: 33.2 vs Easy 32.2 | UK | Mean (SD) in Diff: 30.8 (3.6) vs Easy 27.2 (2.9) | 40 (33.6) |
Yadav, N.K.;2019 [13] | India | Prospective single arm observational trial | 310 | Surgical patients, scheduled for various surgical procedures under general anaesthesia | Range = 18–70 | UK | UK | 35 (11.3) |
Abraham, S.; 2018 [14] | India | Prospective study | 137 | Patients underwent ultrasound followed by surgery under general anesthesia | Mean (SD) = 29.1 (10.5) | UK | UK | 10 (7.3) |
Chan, S.M.M.; 2018 [15] | China | prospective clinical study | 113 | age of 18 years or above, who were scheduled for elective surgery requiring general anesthesia with direct laryngoscopy and tracheal intubation | Range = 19–84; Mean (SD) = 56.1 (12.9) | M = 69 (61.1), F: 44 (38.9) | BMI range: 15.6–52.2 BMI mean (SD): 24.5 (4.9) | 39 (34.5) |
Serbia | Prospective, single blinded, observational study | 301 | undergoing elective surgery under general anaesthesia with tracheal intubation | Mean (SD) = 57.2 (17.2) | M: 156 (51.8), F: 145 (48.2) | BMI mean: 25.8 (5.3) | 28 (9.3) | |
Petrișor, C.; 2018 [17] | Romania | Prospective observational | 25 | Patients with morbid obesity (Body Mass Index > 40 kg m-2, BMI), who needed to be operated on under general anaesthesia with oro-tracheal intubation | Mean (SD) in Diff: 52.0 (12.0) vs Easy: 46.0 (14.0) | In Diff: M: 1 (4.0), F: 3 (12.0) In Easy: M: 8 (32.0), F: 13 (52.0) | BMI mean (SD): Diff: 44.0 (7.6) vs Easy: 45.6 (0.79) | 4 (16.0) |
Rana, S.; 2018 [18] | India | prospective, observational study | 120 | Patients scheduled for elective surgery requiring general anesthesia and tracheal intubation | Mean (SD) in CL1: 43.9 (12.0), CL2: 42.1 (15.3), CL3: 46.6 (9.4), CL4: 45.2 (7.1) | In total: M = 53 (44.2), F = 67 (55.8) In CL1: M: 13 (10.8), F:20 (16.7) In CL2: M: 24 (20.0), F:35 (29.2) In CL3: M: 10 (8.3), F:7 (5.8) In CL4: M:6 (5.0), F: 5 (4.2) | BMI mean (SD): CL1: 22.5 (12.6), CL2: 21.9 (23.2), CL3: 21.6 (20.4), CL4: 22.6 (11.7) | 28 (12.5) |
Yilmaz, C.; 2018 [19] | Turkey | prospective, observational single-center study | 74 | aged > 18 years and morbidly obese (BMI > 35 kg/m2) who were scheduled for laparoscopic weight loss surgery under general anesthesia with endotracheal intubation | Mean (SD) in Diff: 43.3 (5.9) vs Easy 35.7 (8.7) | In Diff: M: 2 (2.7), F: 5 (6.8) In Easy: M: 8 (10.8), F: 59 (79.7) | BMI mean (SD): Diff: 45.2 (2.7) vs Easy: 47.6 (40.8) | 7 (9.5) |
Parameswari, A.; 2017 [20] | India | prospective, double-blinded study | 130 | Patients scheduled for elective surgery requiring general anesthesia and surgery | Range = 18–60, Mean = 37.38 (SD = 12.756) | M: 63 (48.5), F:67 (51.5) | BMI range: 16.5–31.3 | 12 (9.2%) |
Yao, W.; 2017 [21] | China | prospective observational study | 2254 | Patients scheduled for elective surgery requiring general anesthesia and surgery | Mean (Range): In Lar. Diff: 61.0 (28–82) vs Easy: 49.0 (18–83) In Int. Diff: 61.0 (30–80) vs Easy: 50.0 (18–83) | Lar. Diff: M: 102 (4.5), F: 40 (1.8) Lar. Easy: M: 957 (42.5), F: 1155 (51.2) Int. Diff: M: 34 (1.5), F: 17 (0.8) Int. Easy: M: 1025 (42.5), F: 1178 (52.3) | BMI mean (SD): In Lar. Diff: 23.3 (3.3) vs Easy: 22.8 (3.5) In Int. Diff: 23.7 (3.7) vs Easy: 22.8 (3.5) | Diff. lar. =142 (6.3) / Diff. Int. = 51 (2.3) |
Yao, W.; 2017 [22] | China | prospective | 484 | elective surgery patients who were administered tracheal intubations under general anesthesia, ASA physical status I to III, and who were 18 to 90 years old. | Mean (SD) in Diff: 53.0 (14.0) vs Easy 48.0 (14.0) | In Diff: M: 29 (6.0), F: 12 (2.5) In Easy: M: 190 (39.3), F: 253 (52.3) | BMI mean (SD): Diff: 23.8 (3.1) vs Easy: 23.3 (3.6) | 41 (8.47%) |
Andruszkiewicz, P.; 2016 [23] | Poland | prospective observational study | 199 | Patients scheduled for elective surgery requiring general anesthesia and surgery | Mean (SD) in Diff: 52.9 (8.3) vs Easy 51.3 (16.3) | In Diff: M: 10 (5.0), F: 12 (6.0) In Easy: M: 93 (46.7), F: 84 (42.2) | BMI mean (SD): Diff: 27.3 (6.9) vs Easy: 26.7 (5.0) | 22 (11.1) |
Pinto, J.; 2016 [24] | Portugal | prospectivedouble blind study | 74 | ASA class I - III scheduled surgical/ Pregnant & morbid obesit was excluded | Mean (SD) in Diff: 57.5 (11.1) vs Easy: 55.2 (18.1) | In Diff: M: 13 (17.6), F: 4 (5.4) In Easy: M: 26 (35.1), F: 31 (41.9) | BMI mean (SD): Diff: 28.9 (4.7) vs Easy: 27.5 (5.2) | 17 (22.97) |
Reddy, P.B.; 2016 [25] | India | prospective, observational study | 100 | Patients scheduled for elective surgery requiring general anesthesia and surgery | Range = 18–70 | M: 69 (69.0), F: 31 (31.0) | BMI range: 14.2–39.0 | 14 (14.0) |
Canada | UK | 100 | Adult patients (> 17 years old) presenting for elective surgery and requiring routine tracheal intubation | Mean (SD) = 52.1 (15.5) | M: 55 (55.0), F: 45 (45.0) | BMI mean (SD): 28.4 (5.3) | 11 (11.0) | |
Wu, J.; 2014 [27] | China | prospective observational study | 203 | age 20–65 years scheduled to undergo general anesthesia ASA I II | Mean (SD) in Diff: 46.0 (15.0) vs Easy 47.0 [14] | In Diff: M: 14 (6.9), F: 14 (6.9) In Easy: M: 69 (34.0), F: 106 (52.2) | BMI mean (SD): Diff: 25.6 (2.8) vs Easy: 23.6 (3.4) | 28 (13.79) |
India | UK | 49 | patients scheduled for elective surgery and requiring general anesthesia with direct laryngoscopy and endotracheal intubation | UK | UK | UK | 12 (24.49) | |
Adhikari, S.; 2011 [5] | USA | prospective observational study | 51 | Adult patients undergoing endotracheal intubation for an elective surgical procedure | Mean (SD) = 53.1 (13.2) | M: 19 (37.3), F: 32 (62.7) | UK | 12 (23.5) |
Wojtczak, J.A.; 2011 [29] | USA | UK | 12 | Five obese and 7 morbidly obese adult patients with a history of either difficult or easy intubation | Mean in Diff: 36.8 vs Easy. Mean = 36.8 | M: 7 (58.3), F: 5 (41.7) | BMI range: 30.1–52.3, 7patient > 40 | 6 (50.0) |
Komatsu, R.; 2007 [30] | USA | UK | 64 | morbidly obese patients (BMI > 35) scheduled for elective surgery under general anaesthesia with tracheal intubation | Mean (SD) in Diff: 47.0 (9.0) vs Easy: 42.0 (11.0) | In Diff: M: 3 (4.7), F: 17 (26.6) In Easy: M: 9 (14.1), F: 35 (54.7) | BMI mean (SD): Diff: 56.0 (12.0) vs Easy: 57(SD = 15) | 20 (31.3) |
Ezri, T.; 2003 [31] | Israel | UK | 50 | 50 morbidly obese patients (BMI > 35 kg·m − 2) scheduled for laparoscopic weight reduction surgery (LapBand) undergeneral anaesthesia with endotracheal intubation | Mean (SD) in Diff: 33.6 (6.0) vs Easy 38.8 (8.4) | In Diff: M: 7 (14.0), F: 2 (4.0) In Easy: M: 14 (28.0), F: 27 (54.0) | BMI mean (SD): Diff: 44.0 (4.8) vs Easy: 43.0 (4.0) | 9 (18.0) |
Study | Risk of bias | Applicability concerns | |||||
---|---|---|---|---|---|---|---|
Patient selection | Index test | Reference standard | Flow and timing | Patient selection | Index test | Reference standard | |
Daggupati, H.; 2020 [7] | Low | Low | Low | Low | Low | Low | Low |
Martínez-García, A.;2020 [8] | Unclear | Low | Low | Low | Low | Low | Low |
Fulkerson, J.S.;2019 [9] | High | Low | Low | Low | Low | Low | Low |
Koundal, V.;2019 [11] | Unclear | Low | Low | Low | Low | Low | Low |
Wang, L.;2019 [12] | Unclear | Low | Low | Low | Low | Low | Low |
Xu, L.;2019 [10] | High | Low | Low | Low | Low | Low | High |
Yadav, N.K.;2019 [13] | Unclear | Low | Low | Low | Low | Low | Low |
Abraham, S.; 2018 [14] | Unclear | Low | Unclear | Low | Low | Low | Low |
Chan, S.M.M.; 2018 [15] | Unclear | Low | Low | Low | Low | Low | Low |
Unclear | Low | Low | Low | Low | Low | Low | |
Petrișor, C.; 2018 [17] | Unclear | Low | Unclear | Low | Low | Low | Unclear |
Unclear | Low | Low | Low | Low | Low | Low | |
Yilmaz, C.; 2018 [19] | Low | Low | Low | Low | Low | Low | Low |
Parameswari, A.; 2017 [20] | Unclear | Low | Unclear | Low | Low | Low | Low |
Yao, W.; 2017 [21] | Unclear | Low | Low | Low | Low | Low | Low |
Yao, W.; 2017 [22] | Unclear | Low | Low | Low | Low | Low | Low |
Andruszkiewicz, P.; 2016 [23] | Low | Low | Low | High | Low | Low | Low |
Pinto, J.; 2016 [24] | Unclear | Unclear | Low | Low | Low | Low | Low |
Reddy, P.B.; 2016 [25] | Low | Low | Low | Low | Low | Low | Low |
Low | Low | Low | Low | Low | Low | Low | |
Wu, J.; 2014 [27] | Unclear | Low | Unclear | Low | Low | Low | Low |
Unclear | Low | Unclear | Low | Low | Low | Low | |
Adhikari, S.; 2011 [5] | Low | Low | Low | Low | Low | Low | Low |
Wojtczak, J.A.; 2011 [29] | High | Low | Unclear | Low | Low | Low | Low |
Komatsu, R.; 2007 [30] | Unclear | Low | Low | Low | Low | Low | Low |
Ezri, T.; 2003 [31] | High | Low | Unclear | Low | Low | Low | Low |
Predictive ultrasonography indicators for difficult intubation
Distance from the skin to the epiglottis
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 |