LUS assessment
LUS is performed using GE Voluson S10 or Philip EP5 ultrasound equipment
. The frequency of the linear array probe was 10 to 13 MHz.
Lung ultrasound was performed at one of the following timings after
birth: 0.5h, 1h, 2h, 4, 6h. And the performer was a physician who
received two months of formal training. This training includes a 2-day
course and practice on no less than 100 cases under senior
supervision14.
The scanning protocol was based on an adult adaptive
method20 and adjusted for infants. The LUS was
performed in totally ten regions, as shown in Figure S1. Scanning was
performed continuously in each region in case of missing and finished
quacky in case of being disturbed by the motion of infants. A similar
protocol can be seen in other studies21 but we reduced
total twelve regions in theirs to ten regions due to the area of two
lateral(left and right) regions is nearly as large as other eight
regions. The infants may be posed in a supine position, later position,
or prone position if needed. In every region, if any of ”high-risk”
patterns were detected, then the region was marked as ”high-risk”. By
contrast, only when the whole region has no ”high-risk” patterns, this
region can be defined as ”low-risk”. The number of ”high-risk” regions
and ”low-risk” regions were used to assess the reliability of
prediction. The definitions of ”high-risk” patterns and ”low-risk”
patterns were determined by a pre-experiment and were shown in Figure 2.
Results were recorded on a dedicated sheet, not included in patients’
files and masked to other clinicians: this was the best way to mask the
clinical conditions to the colleagues performing LUS and the LUS results
to other clinicians14. The images and its
interpretations for each participant were recorded by the LUS examiner
and were linked to a serial number(SN) from1 to 310(after excluded those
without qualified data). The SNs were then corresponded to infants
outcomes by the physician who offer NICU treatment or follow up these
infants. Finally, an independent data analyst who has no idea of lung
ultrasound analyzed the data.