1. Research Unit for Experimental Neonatal Respiratory Physiology, Cruces Hospital, Plaza de Cruces, Barakaldo, Bizkaia, Spain.
2. Neonatal Intensive Care Unit and the Department of Paediatrics, Cruces Hospital, University of the Basque Country, Barakaldo, Bizkaia, Spain.
3. Department of Electronics and Electrotechnics, High Technical School of Maritime Studies, University of the Basque Country, Bilbao, Bizkaia, Spain.