Assessment of Extubation Readiness in Preterm Infants Using Chest Ultrasound

Study Design and setting:This is a prospective descriptive pilot study that will be conducted on infants born at < 28 weeks gestation who meet eligibility criteria and are admitted to the Neonatal intensive care at Mount Sinai Hospital. Enrolment of eligible infants will start after obtaining approval from Mount Sinai Research Ethics Board and parent's consent.

Time of assessment: Parents of infants on invasive mechanical ventilation who are eligible for the study will be approached for consent. Once the decision made by attending physician to extubate the infant, Chest ultrasound (Lung ultrasound + diaphragmatic function assessment) will be done. Chest ultrasound will be done before next feeding to avoid any interference of a full stomach on diaphragmatic assessment.

Study procedure: Decisions about extubation will be as per the clinical judgment of the physician in-charge of the infant and will not in any way based on Chest ultrasound measurements. A lung ultrasound combined with diaphragmatic function assessment will be done by one of the investigators prior to extubation. The result of Chest ultrasound will be masked for the clinical team to avoid any influence of the Chest ultrasound result on the extubation decision. On the other hand, if the attending physician requests Chest ultrasound for the purpose of the ongoing clinical management or to help with making extubation decision then the result of the study will be disclosed to the physician and this infant will be excluded from the study.

A random sample of 20% of eligible infants will have lung ultrasound scoring and diaphragmatic function assessment done twice by 2 operators (with various levels of Chest ultrasound expertise). None of the operator will be aware of the result of Chest ultrasound done by the other operator for the same patient. Lung ultrasound severity score, diaphragmatic thickness fraction and diaphragmatic excursion will be calculated. Inter-rater agreement will be assessed using raw percentage of agreement (Pa), Cohen's and Kappa (κ), and G wet agreement coefficient (AC1). Intra-class correlation will be determined for variables with continuous measurements (mixed factorial design). High-resolution linear and curvi-linear ultrasound probes of 20-5 and 10-3 MegaHertZ will be used to assess lung ultrasound score and to measure diaphragmatic thickness and diaphragmatic excursion [amplitude] respectively using both B-mode and M-mode.

Lung ultrasound assessment technique: Chest ultrasound will be performed in a standardized manner. A longitudinal scan of the anterior and lateral chest walls will be performed. Three chest areas for each side (upper anterior, lower anterior, and lateral) will be assessed. Each area will have a score of 0 to 4 points with the total score ranges from 0 to 24 which inversely correlating with lung aeration.