Could lying on the stomach help infants breathe easier?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Patients hospitalized at Pediatric Intensive Care Unit (PICU) or Neonatal Intensive Care Unit (NICU) of the Medical University Vienna. * Patients aged \>36 weeks (corrected gestational age) and \<24 months. * Patient intubated and mechanically ventilated for at least 6 hours, with an expected requirement of invasive ventilatory support for at least 12 hours. * Clinical picture strongly suggestive for acute bronchiolitis or pneumonia (fever, fine crackles, prolonged expiration, lung hyperinflation and/or findings of new infiltrates consistent with acute pulmonary parenchymal disease on chest X-ray). * Severe pediatric acute respiratory distress syndrome (ARDS), defined by OSI ≥12.3 (wean FIO2 to maintain SpO2 ≤ 97% to calculate oxygen saturation index). * Written informed consent obtained from parents. Exclusion Criteria: * Clinical context * Need for O2 supplementation to maintain SpO2\>94% in the 4 weeks preceding hospitalization in the PICU/NICU * Cyanotic congenital heart disease Cardiogenic pulmonary edema * Severe pulmonary hypertension * Untreated pneumothorax * Severe neurological abnormalities * Other severe congenital anomalies such as congenital diaphragmatic hernia * Ongoing cardiopulmonary resuscitation or limitation of life support * Contradictions for prone positioning (adapted from Guerin, C., et al., Prone positioning in severe acute respiratory distress syndrome. N Engl J Med, 2013. 368(23): p. 2159-68): * Intracranial pressure \>30 millimeters of mercury (mmHg) in supine position or cerebral perfusion pressure \<60 mmHg * Massive hemoptysis requiring an immediate surgical or interventional radiology procedure * Tracheal surgery or sternotomy during the previous 15 days * Serious facial trauma or facial surgery during the previous 15 days * Deep venous thrombosis treated for less than 2 days * Cardiac pacemaker inserted in the last 2 days * Unstable spine, femur, or pelvic fractures * Use of extracorporeal membrane oxygenation (ECMO) before inclusion * Lung transplantation * Burns on more than 20% of the body surface * Other non-inclusion criteria * Indication not to attempt resuscitation * Patient already recruited for other clinical studies * Patients who already received surfactant in the last 4 weeks * Thoracic skin lesions or wounds on the thorax, where the EIT-electrode-belt would be placed