POCUS of the Pediatric Critical Airway

Overview

The goal of this observational study is to assess the laryngeal air column width difference measurement on point of care ultrasound as a predictive indicator of post-extubation stridor in the pediatric critical care population. The main question it claims to answer is: In pediatric intensive care unit patients, can point of care ultrasound measurements of laryngeal air column width difference be used as a sensitive and specific tool to predict post extubation stridor in comparison to standard qualitative and quantitative evaluations? Participants will be enrolled when they are on or approaching extubation readiness. At this time, an ultrasound of their airway will be performed by the investigators and the laryngeal air column width difference will be recorded.

The pediatric airway is markedly different front that of the adult airway, with unique anatomical challenges that can make endotracheal extubation of the pediatric airway more complicated. Pediatric patients are sensitive to small changes in diameter and patients who have been intubated may experience laryngeal edema. This laryngeal edema is multifactorial, but in large part is caused by mechanical pressure or irritation from the endotracheal tube itself. Mucosal ulcerations and laryngeal edema occur in almost all patients intubated for greater than four days. In pediatrics, the laryngeal edema from endotracheal intubation can lead to upper airway obstruction (UOA) with the development of post extubation stridor (PES), and often, respiratory distress. Early identification of patients who are at high risk for PES is critical, as it allows for proper preparation and prevention of complications. The rates of PES have been estimated between 5% and 54%, widely varied in the literature. Some factors that have been identified as predictive of PES include young age, female gender, previous history of airway difficulties, longer intubation duration, elevated cuff pressure, incorrect endotracheal tube size, airway infection, traumatic intubation, repeated intubation attempts, prolonged intubation, aggressive tracheal aspiration, increased tube mobility, and unintentional extubations. Recently, ultrasound has been used to help predict those patients who may be at risk for PES. Currently, cuff leak tests have been widely used to predict upper airway patency and are currently standard of care in Pediatric Intensive Care Units across the country, however, the positive predictive value of this test has consistently shown to be low. With ultrasound, a measurement of the laryngeal air column width can be used to predict patients who will develop PES. An observational study done in 2018 at a single, tertiary pediatric hospital showed that laryngeal ultrasound done by experienced ultrasonographers and radiologists prior to extubation could predict patients who would develop PES. In critical care, there is a significant need to decrease PES rates and POCUS could provide a rapid, reliable, and sensitive assessment of the pediatric patient who is at risk for PES and its complications. The investigators hypothesize that patients with smaller laryngeal air column width differences on POCUS will have a higher likelihood of developing PES. Ultrasound measurements will be completed as soon as the patient is deemed to perform extubation readiness assessments, as determined by the attending pediatric intensivist. The ultrasound will be performed within 1 to 12 hours prior to extubation, alongside the Respiratory Therapist evaluation of cuff pressure, per standard unit protocol. A high frequency linear phased array probe will be used for obtaining the images with a General Electric (GE) ultrasound machine. Prior to obtaining images, the endotracheal tube will be suctioned per unit standard nursing protocol. Additionally, oral and pharyngeal secretions will be gently suctioned. The linear probe will then be placed on the cricothyroid membrane with a transverse view of the larynx. The scanning plane will contain multiple landmarks, including the vocal cords, the tracheal cartilage, and possibly, the arytenoid cartilages. The laryngeal air column width will then be measured with the endotracheal tube cuff inflated and deflated. The laryngeal air column width difference is the difference between the balloon inflated width minus the balloon deflated width. Three measurements of the laryngeal air column width difference will be taken and averaged for a final value. The presence of PES will be defined by the administration of racemic epinephrine within 6 hours of extubation, as detemined by the extubating physician, who is not a part of the study team.