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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