The present subject matter describes a flow-sensing arrangement within a spirometer (100). The arrangement comprises a tubular-member (202) for allowing an air-passage along a longitudinal-axis thereof. At-least two disc-shaped air-resistive elements (204) are removably-arranged within the tubular member (202) to resist the air-flow. Each of said resistive-elements comprises perforations for allowing the air-passage through the resistive- element. At-least two ports (206) extend radially outward through a wall of said tubular member (202), such that each of said two ports (206) are located within the tubular-member (202) near the resistive-elements (204) to cause determination of at least a pressure- difference there-between.
