Lung Function Decline in Smokers and Nonsmokers

The natural history of lung function decline. Smokers who are susceptible to lung injury experience an increase in the rate of age-related loss in FEV1 compared with nonsmokers (red, green, and blue lines). After lung function declines to threshold levels, clinical symptoms develop (black dotted lines). When a smoker stops smoking, the rate of FEV1 loss again approximates to that of a nonsmoker (blue dotted line). (FEV1 = forced expiratory volume in one second.)






GOLD Staging System for COPD Severity

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Stage	Description	Findings*
0	At risk	Risk factors and chronic symptoms but normal spirometry
I	Mild	FEV1/FVC ratio less than 70 percentFEV1 at least 80 percent of predicted valueMay have symptoms
II	Moderate	FEV1/FVC ratio less than 70 percentFEV1 50 percent to less than 80 percent of predicted valueMay have chronic symptoms
III	Severe	FEV1/FVC ratio less than 70 percent FEV1 30 percent to less than 50 percent of predicted valueMay have chronic symptoms
IV	Very severe	FEV1/FVC ratio less than 70 percentFEV1 less than 30 percent of predicted value
			or
		FEV1 less than 50 percent of predicted value plus severe chronic symptoms