College Answer

This topic required a definition and understanding of airways resistance. It was expected candidates could identify that issues around the nature of flow (turbulent vs. laminar) and airway diameter were central determinants. It was expected candidates would describe the determinants of turbulent flow.The provision of formula and comments about Reynolds number helped demonstrate an understanding of this. Better answers discussed the transitional point in the airway and the paradox about size vs. total cross sectional area and its influence on total resistance. Several candidates confused pulmonary vascular resistance with airways resistance. Using graphs to help illustrate certain concepts would have been helpful. Measurement of resistance (indirectly via measurement of flow and pressure difference by a body plethysmography, spirometry) and detection of flow (spirometry, capnography) was in general poorly understood.