ABSTRACT
A number of different liquids and gases are given to patients during a routine anaesthetic and the physical properties of flow are essential to healthcare professionals' practice. Flow is proportional to the pressure drop and radius to the power of 4 of the tube and inversely proportional to the length of tube and the viscosity of the fluid. In fluid dynamics, the Bernoulli principle refers to a lowering of fluid pressure in regions where the flow velocity increased. The entrainment ratio describes the ratio of entrained flow to driving flow. Wright respirometer actually measures gas volumes but flow can be calculated by measuring the volume of gas per unit time. Pneumotachograph a constant orifice, variable-pressure device used to measure flow. Fluidics is the technology of using the flow characteristics of a liquid or gas to perform analogue or digital operations similar to those performed by mechanical or electronic systems.
