9
FVC >5th percentile?
Possible mixed disorder Airflow obstruction
Need lung volumes
YES
NO
NO
Comments
TLC reduced to confirm
TLC normal: Additional testing may be helpful (e.g., BDR, Raw).
When TLC is not available, this pattern has been described in population-based studies as
preserved ratio-impaired spirometry (PRISm) in current and former smokers.
Lack of sharp peak expiratory flow (PEF)
Lack of sharp PEF
Need lung volumes to confirm
May be normal variant
If it is normal, then spirometry is normal, but if it is low then there may be possible restriction. is
must be determined by measurement of TLC. If the TLC is low, then spirometry is consistent with
restriction. If restriction is ruled out by a normal TLC, then the pattern of abnormality of low FVC
with normal FEV
1
/FVC has been dubbed the possible restriction or non-specific pattern, which
may include diseases causing obstruction or restriction. Restriction presenting as the "non-specific"
pattern is oen caused by a chest wall or neuromuscular disorder.
