Fig. 5: Glottis patency throughout the breathing cycle in a single preterm newborn rabbit kitten exposed to room air and then 100% oxygen.

An oesophageal catheter (mid-thoracic region) was used to measure intrathoracic pressure changes during breathing efforts after birth. Breathing patterns were continuously recorded and the glottis was assessed for patency while the kitten was exposed to a continuous positive airway pressure in room air (21% oxygen) and then 100% oxygen. The specific times during the breathing cycle when the glottis was observed to be open has been highlighted in green and in pink when closed. In air (a), the glottis was predominantly closed and opened only briefly during inspiration (~16% of the time). When first exposed to 100% oxygen (b), breathing efforts after one minute were more frequent and the glottis was observed to be open for longer in-between breaths (~52% of the time). After being exposed to 100% oxygen for 5 min (c), breathing efforts were more frequent and the glottis was open throughout the entire breathing cycle (100% of the time).