Fig. 1
The bench model and experimental protocol. Panel (a) Each glass chamber had two openings: one for introducing the balloon into the chamber and the other one for adjusting and measuring the chamber pressure. Panel (b) Balloon volume tests were performed in five chambers with respective inner volume of 1000, 500, 250, 175 and 125 ml. In each chamber, baseline pressure was adjusted to 5, 10, 15, 20, 25 and 30 cmH2O. Before each balloon volume test, connections in the chamber system were sealed by silicone sealant, and systematic leaks were checked