Mathematical Behavior of MEFV Curves in Childhood Asthma and the Role of Curvature in Quantifying Flow Obstruction

Figure 1

Examples of MEFV curves (each subplot illustrates a patient spirometric tracing). Coordinates are as shown in the top left corner subplot ((o) raw data; (-) smoothing spline). By visual inspection, one may qualitatively infer upon the degree of curvature of the descending limb: from quasi linear (second row, first column) to convex (fourth row, second column). Note that some examples illustrate an MEFV curve stopping abruptly at the end of the expiratory maneuver (third row, second column) or characterized with a second peak flow (fourth row, first column).