Difficult Airway Assessment in Veterans Using Sonography Study

Background• Current difficult airway predictors have limited sensitivity and

specificity• The “difficult airway” is not a single entity but a constellation of

provider competency, ventilation, intubation and laryngoscopy• Provider interest in sonography utility for airway management

has been appearing in the literature• Ultrasound visualizes airway structures comparable to CT scan• Cormack-Lehane Grades (CLG) III & IV define difficult

laryngoscopy• Ten studies have evaluated sonography utility for difficult

laryngoscopy prediction with conflicting results at sonographic hyomental distance and anterior neck depths to hyoid bone, thyrohyoid membrane, and vocal cords

Research Questions• In the Veteran population, how do sonographic measures of the

anterior neck compare with standard physical assessment indicators for prediction of a difficult laryngoscopy?

• Does the use of ultrasonography change the accuracy of detecting a difficult airway compared to standard difficult airway indicators?

Methods• Prospective, cross-sectional, within-subjects study at the

Memphis VA Medical Center with IRB approval from February 1st to June 4th 2016

• Three hour sonographer workshop completed for protocol development and reliability assessment

• 144 Veterans ages 19-79 across all surgical specialties requiring direct laryngoscopy and neuromuscular blockade without history of difficult intubation or airway malformation

• Difficult airway predictors (Results) collected in anesthesia preoperative clinic and CLG collected day of surgery

Statistics & Discussion• Pearson R for intra- and inter-class reliability among

sonographers is high (.940 to .991) • Comparison analysis (T2) using two-tailed independent t-test

(continuous data) and Chi-square/Fischer’s Exact (nominal data). Only neck circumference was significant (p = 0.016)

• Correlation analysis (T3) using Spearman’s correlation significant at HMB:HB (p = 0.040) & HB:THM (p = 0.044) but weakly correlates (-.172 & .168) respectively

• Ultrasound measures or ratios do not perform well as single-items predictors for difficult laryngoscopy

• Difficult laryngoscopy is a corollary to, but not synonymous with, difficult intubation

• With a larger subject population, our results refute those findings by other researchers at all four measurement locations

Heather Moore, BSN, RN; LT Justin Fulkerson, MSN, ACNP-BC; Robert Lowe, BSN, RN; Tristan Anderson, BSN, RN; Lisa Lucas, DNP, CRNA; Jonathan Reed, DNP, CRNA

CLG

Range / Number Mean ± SD / Percent Age 29 – 78 59.56 ± 10.40 years

Sex Male Female

13014

90.3%9.7%

Race Asian Black

White

17073

0.7%48.6%50.7%

BMI 17.10 – 46.00 30.58 ± 5.33

Neck Circumference 34.00 – 58.00 47.92 ± 5.28 cm in BMI ≥35CLG I

IIaIIbIIIIV

59452596

41%31.3%17.4%6.3%4.2%

Easy (n = 129) Difficult (n = 15) p - valueAge 59.81 ± 10.62 years 57.40 ± 8.22 years .398Sex Male

Female11613

141

.673

BMI 30.54 ± 5.48 30.88 ± 4.00 .818Neck Circumference (n = 27) 48.60 ± 4.62 cm

(n = 25)39.50 ± 7.78 cm (n = 2)

.016

Standard IndicatorsDiagnosed OSA No

Yes9435

96

.296

Snoring NoYes

5574

510

.489

Upper Teeth Abnormal NoYes

10425

132

.737

Jaw mobility Abnormal NoYes

1272

132

.054

Interincisor Gap <4cm NoYes

1227

123

.071

Mallampati Grade 1234

4773 90

310 2 0

.369

Thyromental distance <6cm

NoYes

1114

14 1

0.615

Neck ROM < 90 degrees NoYes

1209

14 1

0.964

Sonographic MeasuresHyomental distance(HMD) 5.28 ± 0.69 cm 5.10 ± 0.65 cm .341

Hyoid Bone(HB) 0.97 ± 0.31 cm 0.93 ± 0.22 cm .681Thyrohyoid Membrane(THM) 2.14 ± 0.48 cm 2.00 ± 0.47 cm .304

Vocal Cords(VC) 0.70 ± 0.23 cm 0.73 ± 0.15 cm .631Sonographic Ratios

HMD:HB 6.12 ± 2.7 5.05 ± 1.73 .139HMD:THM 2.62 ± 0.85 2.55 ± 1.03 .749

HMD:VC 8.25 ± 2.92 6.87 ± 2.62 .080HB:THM 0.47 ± 0.17 0.49 ± 0.14 .606

HB:VC 1.47 ± 0.59 1.37 ± 0.46 .482THM:VC 3.30 ± 1.24 2.85 ± 0.82 .174

HMD HB THM VC HMB:HB

HMB:THMB

HMB:VC

HB:THM

HB:VC

THM:VC

R -.116 .095 -.061 .137 -.172 -.010 -.134 .168 .007 -.134p - value .168 .260 .470 .102 .040 .901 .108 .044 .934 .109

Easy vs. Difficult Group Differences (T2)

Sample Demographics (T1)

Correlation Analysis (T3)

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Anterior

Posterior

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This material is the result of work supported with resources and the use of facilities at the Memphis Veterans Affairs Medical Center. The authors represent the San Diego, Dallas, Denver, Temple, and Memphis VA Medical Centers, respectively. The contents of this poster do not represent the views of the U.S. Department of Veterans Affairs or the United States Government.