Ultrasonographical Assessment of Airway Indices in Pregnancy

Tracheal intubation (TI) through direct laryngoscopy is often performed in patients to establish an airway to provide adequate ventilation and oxygenation, and/or to protect the airway from aspiration of oral and pharyngeal secretions. Difficult intubation occurs due to insufficient vision of the larynx during direct laryngoscopy. Some constraints such as full stomach and aspiration risk, unknown past medical and allergy history may make the actual number of difficult intubation in operating room. It seems that, to prevent complications due to repeated attempt for intubation (arrythmia, hypoxia, …), early detection of probable difficult laryngoscopy cases is of great importance in the operating room. Therefore, various screening methods and scales have been defined in this regard . Cormack-Lehane classification and Mallampati are among screening methods that is used to predict difficult airway and laryngoscopy cases; However, all have considerable limitations . Therefore, the search for a simple, non-invasive technique that provides a more accurate assessment of the patient's airway still continues. The ideal method is expected to be fast, accessible, simple and non-invasive .Today, portable ultrasound devices are widely available in OR and recently studies have focused on its capabilities in terms of airway management . At present, airway ultrasonography is not yet used as a common method for airway assessment. Although several parameters of airway ultrasound have been mentioned in various studies as difficult airway prediction indicators, research is still ongoing to obtain easy and accurate measures . Therefore, this study performed to investigate the relationship between some upper airway ultrasound assessment parameters with difficult laryngoscopy / difficult intubation in pregnant and preeclamptic females and aim to use these parameters to assist physician to decide about difficult laryngoscopy/ difficult intubation and consider as predictors beside the traditional methods.

The first step in airway management is the assessment of various airway indices. Various anatomical and physiological factors place pregnant females at greater risk of airway management complications and difficult intubation. Hypertensive conditions of pregnancy are associated with aggravated changes in the airway, including a narrower upper airway compared with healthy pregnant females. In routine clinical practice, quick and easy bedside assessments are performed pre-operatively to evaluate the airway. These methods have high interobserver variability and only fair to moderate sensitivity and specificity. The role of ultrasound in airway assessment is encouraging as anatomical structures can be visualised in supraglottic, glottis and subglottic views. With the development of better probes, high resolution imaging, real-time pictures and clinical experience, In this prospective study, we assessed the airway indices of non-pregnant, normotensive pregnant and preeclamptic pregnant females using both clinical parameters and ultrasonographic assessment.

• Assessment of laryngoscopic view [Time frame: preoperative just before endotracheal intubation]
• Tongue thickness [Time frame: Once just before induction of general anesthesia]
• Hyoid bone visibility [Time frame: Preoperative just before induction of anesthesia]