Evaluation of ultrasound airway assessment parameters in pregnant patients and their comparison with that of non-pregnant women: a prospective cohort study.

BACKGROUND

Clinical airway assessment parameters differ significantly between pregnant and non-pregnant patients, however literature comparing their ultrasound (US) airway parameters is limited. We planned a prospective cohort study to compare US-assessed airway parameters between pregnant and non-pregnant women.

METHODS

We enrolled 82 pregnant females scheduled for elective cesarean section under neuraxial anesthesia and 80 age-matched non-pregnant females scheduled for elective surgery. Pre-operative clinical airway assessment was performed in both groups. The US airway assessment was done pre-operatively in non-pregnant and postoperatively in pregnant patients. Our primary objective was to compare US-assessed parameters, and secondary objectives included a comparison of clinical airway assessment parameters and investigating a relationship between a difficult airway (defined as a modified Mallampati grade (MMG) ≥ 3) and other airway assessment parameters.

RESULTS

Among several US airway parameters, pregnant patients had significantly higher hyomental distance, anterior neck soft tissue thickness at the hyoid and vocal cord level, and oral cavity height, while the tongue thickness and mandibular condylar movements were significantly lower than in non-pregnant patients. Similarly, for the clinical airway assessment, pregnant patients had significantly higher MMG and upper lip bite test scores, mentohyoid distance, and neck circumference. Pregnancy, the ratio of pre-epiglottic space and epiglottis-to-vocal cords distance (Pre-E/E-VC), and hyoid bone visibility were independent predictors of a difficult airway.

CONCLUSION

The US airway assessment parameters differ significantly between pregnant and non-pregnant patients. Pregnancy, hyoid bone visibility, and Pre-E/E-VC ratio were independent predictors of the difficult airway in female patients.