Abstract
Respiratory distress syndrome is the major cause of mortality in premature babies. Increasing numbers of neonates are now surviving the disease due to advances in techniques used in neonatal intensive care units. Mechanical ventilation is an essential part of the treatment for respiratory distress syndrome and is an area in which improvements and modifications are constantly being made. In the early 1980's a new infant ventilator was introduced involving ventilation by a distal jet. As yet, the mechanisms by which the distal jet ventilator enhances gas exchange are unknown. Original experiments are carried out to record the attenuation and speeds of the pressure wave produced by the distal jet ventilator. The observed changes in wave shape and the high wave speed imply that the ventilator produces waves operating within an acoustic regime. An understanding of the gas exchange mechanisms active in shock assisted ventilation is initiated by a comprehensive investigation of the transport properties of acoustic waves. The advection and diffusion that result from a linear concentration gradient in an acoustic flow are analysed, from the Eulerian and Lagrangian viewpoints. The Eulerian investigation shows that the total flux of tracer through a given pipe can be optimized by choosing the frequency appropriately. The Lagrangian transport is increased as both frequency and radius increase. For all values of parameters, Lagrangian streaming is observed, with a steady net flow in the pipe core away from the tube entrance and an opposing net flow near the tube walls.