Welch Allyn PneumoCheck Operating Instructions Manual page 57

2. Next, find the table entries for a male 20 years old, and calculate
the FVC.
FVC = (0.0739 x 20 years) + (0.0590 x 182.9 cm) - 6.8865
FVC = 1.478 + 10.79 - 6.8865 or
FVC = 5.38 liters
This patient would have an abnormally low FVC if his actual FVC
was less than the "lower limit of normal", which is calculated using
the entry from the LLNF column as follows:
Lower Limit of Normal = Value x LLNF (for LLNF > 0) or
Lower Limit of Normal = Value + LLNF (for LLNF c 0)
For example, our 20 year old male would have a lower limit of normal
for his FVC of :
Lower Limit = 5.38 x 0.798 = 4.29 liters
This means that if his actual FVC is lower than 4.29 liters, it is
considered to be abnormally low. Conversely, if his actual FVC is
larger than 4.29 liters, his FVC is considered to be in the normal
range.
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