This is proportional to gas density and to the square root of the driving pressure. Turbulence is predicted by the Reynolds number, which is equal to vd /r, where v = velocity of gas flow, d = the diameter of the cylinder, and r = the kinematic viscosity of gas flow in a cylinder. When the number is under 2000, flow is usually u laminar and gas flow is proportional to gas viscosity and to the driving pressure. 3
When the number is greater than 4000, gas flow is turbulent. Intermediate values 3
are associated with transitional flow. i r l
The inhalation of Heliox (a mixture of 20%-40% oxygen and 60%-80% helium) can reduce the work of breathing by: Reducing the pressure gradient required to generate a given airflow rate by the fact that it is a low density gas, the density being lower than that of any other gas except hydrogen. The mixture has a density one third of that of air. Reducing the Reynolds number favouring conversion of turbulent to laminar flow in the upper airways.
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