A general theoretical model of growth and decline of lung function with time. Curve A (red) shows normal change over time. Curve B (blue) indicates reduced lung growth and therefore a decrease in the peak level of lung function. Curve C (green) shows a premature decline in lung function, while Curve D (orange) depicts an accelerated decline in lung function. The horizontal gray line represents the development of COPD.
Adapted from Weiss, ST, Sparrow, D (Eds), Airways Responsiveness and Atopy in the Development of the Obstructive Airways Diseases, Raven Press, New York, 1989.
