The change in FEV1 over time may give an indication of future prognosis for a patient with chronic obstructive pulmonary disease (COPD).



(1) FEV1 at various points over time

(2) time intervals in months between the FEV1 readings


change in FEV1 at a given time =

= (FEV1 in liters at given time) – (FEV1 in liters at baseline)


time interval in years =

= ((date at given time) – (baseline date)) / 365


change in FEV1 in mL per year =

= (change in FEV1 in liters) * 1000 / (time interval in years)


slope of FEV1 change =

= SLOPE(change in FEV1 in mL, change in time in years)



• The FEV1 tends to decrease with age.

• In a person with worsening COPD the decline with be greater than normal.


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