The Description of Lung Ultrasound From Initial Neonatal Transition in Very Preterm Infants

This will be a single centre observational study at the Royal Women’s Hospital. We plan to obtain serial lung ultrasound images in premature infants less than 29 weeks starting with in the delivery room through the first 48 hours after birth so that we can describe the appearance of the lungs during neonatal transition. A secondary outcome is to investigate if early lung ultrasound can predict the level of respiratory support the infant will need in the first days after birth. The primary investigator will be responsible for recruitment for this study. If the primary investigator is not available, designated, experienced co-investigators may approach the family for consent. Consent will be sought after initial assessment of the obstetric team. No woman in physical distress will be approached for consent. Families will only be approached after discussion and permission with the midwife and obstetrician responsible for the care of the expecting mother. We understand that the potential delivery of an extremely premature baby is a stressful event. We want to ensure that it is appropriate to approach the family prior to seeking consent. Infants will be excluded if they have a congenital abnormality that affects the lungs, like congenital diaphragmatic hernia. Infants will be excluded if their parents decline to give consent to this study. We will also exclude the infants of parents who cannot speak English. Equipment We will obtain serial LUS images, using a GE Venue 50 (Phillips, USA) ultrasound machine and a “hockey stick,” L8-18i linear transducer with an initial depth of 2cm and a gain of 60. Images will be interpreted, graded, and recorded during or immediately after each LUS exam by the ultrasonographer. We plan to obtain 3 second lung ultrasound video clips of the right and left side of the chest between birth and 10 minutes after birth, between 10-20 minutes after birth, at 1-3 hours after birth (after being stabilized in the NICU) and at 24-48 hours after birth. Additionally, if the baby is intubated for surfactant delivery, we plan to obtain images after intubation, immediately prior to surfactant delivery and after surfactant delivery (targeting 30 minutes to 3 hours depending timing of cares and infant wellbeing) and immediately prior to the first extubation attempt as well as after extubation (targeting 30 minutes to 3 hours depending on timing with cares and infant wellbeing). Other data will be collected from the newborn’s medical chart, included gestational age, weight, exposure to antenatal steroids, time of umbilical cord clamping, presence of maternal chorioanmionitis, APGAR scores, need for resuscitation, umbilical cord blood gases, first recorded temperature, mode of delivery, respiratory support parameters, and other short term outcome data until discharge from the hospital. Lung Ultrasound Exam Technique Babies will be examined in the delivery room on the warming bed or in the isolate in the NICU. We aim to minimize any potential interference with neonatal stabilization. We will ask permission from the treatment team prior to all study investigations. We will attempt to limit data collection to less than 2 minutes of direct patient contact (either touching the baby directly or with the isolate doors open) during each time point. During each exam, the LUS probe will be placed in the baby’s axillae with the notch pointed superiorly towards the baby’s head. The probe will then adjusted until a “bat sign” is achieved and the lungs appeared as aerated and dry as possible. The “bat sign” describes the appearance of white, hyperechoic pleural line dipping below the hypoechoic, black rib shadows that resembles a bat in flight. The probe we will use for image collection is 3.5cm long and a typical image included the lung parenchyma from 4-5 rib spaces in this population. We will place the LUS probe in the baby’s axillae because we feel we can obtain consistent images regardless of the baby’s position, either prone or supine, while minimizing handling which is relevant to a baby in the intensive care setting. Lung Ultrasound Grading The degree of lung aeration and fluid can be graded as type 0, 1, 2, or 3. Type 0 is the appearance of the lungs with a lack of air in the lung tissue (atelectasis) and has been noted in premature infants prior to intubation. This is a “true” lung ultrasound image with no air-based artifact. Type 1 represents consolidated, white-out lungs seen in RDS. Type 2, which is the presence of vertical B-lines arising from the pleural lines (“lung rockets” or “comet tails”), represents partial fluid resorption in the neonatal lung and is not associated with respiratory distress syndrome or non-invasive ventilation failure. Type 3, indicated by A-lines with the presence of lung sliding, represents an aerated, dry lung expected to be seen in healthy lungs. A-lines are artifacts created by ultrasound beams hitting air. Ultrasound beams reverberate off of the air and create a series of horizontal, hyperechoic lines that are equidistant to the distance between the skin and pleural. A-lines are also seen in pneumothorax. Healthy lung and pneumothorax can be differentiated by the presence of normal lung sliding in the healthy lung, seen as characteristic movement of the pleural line on 2-D video loops or the “seashore sign” on M-mode. Lung ultrasound clips will be independently collected by an investigator. Two 2-D clips and 2 images captured with M-mode for each exam will be de-identified, coded, and blindly graded by 2 consultants with expertise in ultrasonography. The degree of lung aeration will be assigned based on the grade of these images at type 0, 1, 2, or 3 using a previously published grading system. In the event of a disagreement in grading, if 2/3 evaluators agree, that grade will be assigned. If all three evaluators assign a different grade, we will review the images openly in a group discussion. We will test inter-rater reliability of characterizing lung ultrasound images as type 0, 1, 2, or 3 by having the three blinded ultra-sonographers independently evaluate each ultrasound clip using a Spearman’s rank-order test. Safety Monitoring If the investigators observe any concerning findings on lung ultrasound (evidence of pneumothorax or effusion), they will immediately notify the clinical team caring for the baby. We will review the data collected after enrolling 10 and 20 babies. The purpose will be to review for adverse outcomes, quality of ultrasound images, efficacy of data collection and grading. Specifically, we will monitor the baby’s first temperature collected by the clinical team, the potential of interfering with patient care, review the quality of ultrasound images using different exam techniques and settings (like location of ultrasound probe, gain, and depth), and the inter-relater reliability.