General Medical Information

Measurement of Nasal Resistance

Thomas V. Mccaffrey

Nasal resistance is the numerical relation between transnasal pressure and flow. Pressure (P) divided by flow (V) is resistance (R), as follows:

R = P/V

The previous description of laminar flow showed that the relation between pressure and flow (resistance) is a constant; however, during turbulence, orifice flow, or flow in a collapsible tube, resistance depends on flow rate, and a nonlinear relation results. Therefore, the numerically calculated resistance varies from point to point along the pressure-flow curve. To obtain a consistent value of resistance that can be compared, it is necessary to specify a specific point on the pressure-flow curve to calculate resistance. In the accepted method, a specific pressure point (usually 150 or 300 Pa) is selected, and flow is measured at this point.