The study was a prospective observational study including 40 neonates suffering from respiratory distress of different etiologies and requiring mechanical ventilation regardless of their gestation age at the time of admission. Patients with proven congenital heart disease, chest deformities, multiple complex congenital anomalies, neurological affection (i.e., Hypoxic-ischemic encephalopathy or intracranial hemorrhage) and congenital infections were excluded from the study. The study was conducted in the NICU unit at our institution, starting in June 2016 and ending December 2016. Ethical committee approval of our institution was obtained and informed consent was taken from the parents or guardians of the patients.
Patients were subjected to history taking (prenatal, natal and post-natal), general and local examination of the chest, heart, and abdomen as well a neurological examination. Laboratory investigations included complete blood picture, serum C-reactive protein, serum electrolytes, and capillary blood gases.
Imaging investigations included plain radiography of the chest at admission and daily for follow-up. Radiographs were performed in the supine anteroposterior position using a mobile X-ray machine and computed radiography plates.
Lung ultrasound was performed using the multi-frequency superficial linear probe (6–12 MHz) installed on the Siemens Acuson X300 ultrasound machine (Siemens Health Care GmbH, Erlangen, Germany). Lung ultrasound was performed at least three times, at admission, before changing ventilation mode and before extubation. Additional scans were required in patients showing deterioration after changing the ventilation mode for follow-up and re-assessment. The lung ultrasound score proposed by Bouhemad et al.  was used to standardize the examination for all patients. Each hemithorax was divided into 6 regions, summing 12 zones for both sides. Upper and lower halves which were further divided into anterior, medial, and lateral zones. The anterior zone is between the medial aspect of the sternum and the anterior axillary line, the medial zone between anterior and posterior axillary lines, and the posterior zone posterior to the posterior axillary line. The probe was applied along the intercostal spaces in each zone, and the degree of aeration was assessed and given a score according to the findings. Normal aeration showing A-lines and lung sliding was given a score of 0, 3, or more separated B-lines denoting mild aeration loss were given a score of 1, marked aeration loss showing coalescent B-lines or curtain sign was given a score of 2 and lastly if lung consolidation was present it was given a score of 3. The maximum score for both lungs was 36. Ultrasound examinations were performed by a radiologist with an experience of more than 15 years in the field of pediatric imaging and ultrasound. In a case of emergency, examinations were performed by the senior radiology resident on call, trained by the radiologist. Images of the lung zones were stored on the machine and later revised by a radiologist. The entire examination took less than 10 min to perform. The decision of weaning patients in this study was not dependent solely on the lung ultrasound scores but on several clinical, biochemical, and radiological parameters.
Patients were mechanically ventilated using assist/control (AC) ventilation in 29 patients and sync intermittent mechanical ventilation (SIMV) in 11 patients. The 29 patients on AC ventilation mode were then switched to SIMV before weaning and extubation. Patients were followed up clinically for 48 h after extubation for assessment of its success or failure and the need for reintubation and mechanical ventilation.
Statistical analysis included descriptive statistics for age, weight, and frequency of variables. Analytic statistics included the Mann-Whitney U test for comparison between the groups and ROC curve analysis. Statistics were performed using Medcalc 18 statistical software (MedCalc Software bvba).