At birth, the lungs of preterm infants are most vulnerable. Current recommendations in respiratory support at birth are based on few data and little distinction has been made between term and... Show moreAt birth, the lungs of preterm infants are most vulnerable. Current recommendations in respiratory support at birth are based on few data and little distinction has been made between term and preterm infants. The aim was to gather data that could lead to a better understanding of spontaneous breathing and improvement of the respiratory support of preterm infants at birth. We report that preterm infants at birth use expiratory braking and breath holds to create and defend their functional residual capacity (FRC). It is possible we should mimic these strategies when respiratory support is needed. Applying positive end expiratory pressure (CPAP) in spontaneous breathing preterm infants at birth is feasible and not detrimental, providing early surfactant is given. Experimental studies in this thesis showed that applying positive end expiratory pressure is essential for creating and maintaining FRC during ventilation of preterm infants at birth. Also, an initial sustained inflation of 10-20 seconds at birth creates an immediate FRC and more uniform lung aeration. Combining these strategies has led to a more efficient approach in preterm infants than repeated manual inflations with a self-inflating bag and mask. This thesis contributed to the accumulating evidence for a different approach than currently recommended. Show less