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.