Materials and Methods
This prospective observational study was conducted between January 2022 and December 2022 in a 61-bed NICU. The ethical approval was obtained from the ethics board of the hospital. The written informed consent was obtained from the parents of each participant before lung USG.
Newborns who were hospitalized in the NICU during the study period and treated with HFOV for any cause (as primary or rescue therapy) and for whom parental consent was obtained were included in the study. The study did not include those without parental consent and those with chest deformities, congenital lung malformation, or diaphragmatic pathology. Weeks of gestation, birth weights, and postnatal ages of the patients were recorded.
The patients were followed on HFOV using Leoni Plus devices (Courtesy of Löwenstein Medical Technology, Bad Ems, Germany). Generally CXR is obtained to assess lung aeration after mechanical ventilator adjustments in accordance with procedures.
Lung USG was performed right before CXR, using pre-warmed gel on the linear probe (13 MHz) of a portable ultrasonography device (Esaote, Mylab Seven, 201236) while the baby was in the supine position within the incubator. The linear probe was placed in the longitudinal plane on the right mid-clavicular line, and the ribs were counted by advancing in the craniocaudal axis without lifting the probe from the chest until the right hemidiaphragm was observed (Picture 1). In order to avoid alterations in lung mechanics due to positional changes, we evaluated the ribs on anterior aspect. Each patient had a single measurement. Throughout the examination, the optimal blood oxygenation and body temperature are maintained.
To minimize variability, all USG measurements were performed by a single neonatologist who had received two weeks of training from a radiologist on the use of the equipment and anatomical landmarks of the chest before the onset of the study.
CXR was performed in an anterior-posterior position immediately after lung USG using a portable X-ray device (Siemens, Mobilet Miramax, 3638, 1015544537) by the radiology technician. The CXR image, which had been digitized in the hospital system, was examined by another neonatologist who was blinded to the thorax USG findings. To assess lung aeration, the posterior costae in the right hemithorax were counted in the craniocaudal direction, until the level of the hemidiaphragm and recorded. The localization of the posterior part of the right diaphragm positioned at the level of the 9th costa was considered as the landmark for optimal lung expansion during HFOV[8]. Following validation with CXR, which is still regarded as the gold standard, corrective steps for HFOV were performed.