Study Design
After obtaining approval from the Ethics Committee of the Dokuz Eylul
University Faculty of Medicine, we performed a prospective study between
December 2018 and May 2019. Written informed consent was received from
the parents or legal guardians of patients before enrollment. The study
was conducted in the Dokuz Eylul University Pediatric Emergency
Department. Previously healthy children aged between 1 and 24 months and
diagnosed with AB according to the guidelines of the American Academy of
Pediatrics were included in the study. The following patients were
excluded: those requiring immediate intervention with life-threatening
disease, patients with a history of recurrent wheezing (more than 3
attacks) or one major criterion or two minor criteria according to the
Modified Asthma Predictive Index, and those with chronic respiratory
disease, cardiac or neuromuscular diseases, genetic disorders, chest
wall abnormalities, prematurity (<34 gestational week), or a
history of cardiac or thoracic surgery ²². The demographic and clinical
data were recorded and the patients were grouped to quantify the
severity of AB using the Modified Respiratory Distress Assessment
Instrument (mRDAI) score, a scale that consists of respiratory rate, use
of accessory muscles, auscultation findings, and color, with each
parameter scored from 0 to 3 and the total score being categorized as
mild (0-4 points), moderate (5-8 points), or severe (9-12 points) for
bronchiolitis patients ²³. Vital signs were monitored by a nurse and the
patients were evaluated by a pediatric assistant and a pediatric
emergency fellow.
Sonographic examination was performed with a Philips ClearVue 350
portable system with an L12-4 MHz linear transducer by a single
pediatric emergency fellow who was well trained on LUS for over 2 years.
Sonographic examinations were obtained when the participants seemed
calm, using pacifiers or distracting their attention somehow during the
examination. If they were uncooperative, we waited until they looked
calm or fell asleep. Lung ultrasound was performed following a process
reported previously ²⁴. Both longitudinal and transverse sections were
obtained for the anterior, posterior, and lateral chest wall and the BUS
was calculated using the methodology described by Basile et al. ¹⁰ based
on the extent of lung involvement (Figure 1). Echographic findings of
bronchiolitis were examined for anterior and paravertebral/posterior
areas of the thorax and each parameter was scored with 0 to 2 points.
The total score was assessed as 0 point: normal lung ultrasound pattern;
1-3 points: mild bronchiolitis, 4-6 points: moderate bronchiolitis; or
7-8 points: severe bronchiolitis ¹⁰.
The right hemidiaphragm was examined for sonographic evaluation as
previous studies detected that there was no difference between the
measurements of right and left sides ²⁵ˉ²⁷. The transducer was located
on the midaxillary or midclavicular line, between the 9th and 10th
intercostal areas in the coronal plane and directed medially, cephalad,
and dorsally to achieve the best image. The two-dimensional mode was
used to identify the diaphragm and M-mode was then used to measure the
thickness and display diaphragmatic movement. The diaphragm was imaged
as an echogenic line moving freely during inspiration and expiration in
M-mode. Inspiration was detected as upward and expiration as downward
flexion on the sonographic tracing. The thickness of the diaphragm was
measured by the vertical distance between the midpoints of the pleural
and peritoneal layers at the end of inspiration and expiration. The
thickening fraction (TF) was calculated as (TEI – TEE)/TEE, where TEI
is diaphragm thickness at the end of inspiration and TEE is diaphragm
thickness at the end of expiration, and it was recorded as a percentage.
Diaphragm excursion (EXC) was measured as the vertical distance tracing
from the baseline to the point of maximum height of inspiration.
Inspiratory slope (IS), or the speed of diaphragmatic contraction, and
expiratory slope (ES), or the speed of relaxation, were calculated
together with the total duration time of the respiratory cycle (Figure
2). Three consecutive respiratory cycles were recorded and the averages
of 3 cycles were calculated for each parameter ¹⁸.
The primary outcome of our study was to determine DUS parameters in
bronchiolitis patients and the secondary outcome was to identify the
correlations between DUS parameters and clinical and sonographic
severity scores, need for respiratory support, and outcomes.