FVC to slow inspiratory vital capacity ratio: a potential marker for small airways obstruction.
BACKGROUND
The ratio of FVC to slow inspiratory vital capacity (SVC) has been reported to reflect small airways obstruction, but its validity as such is still unclear. The aim of this study was to assess the applicability of the FVC/SVC ratio as a marker of small airways function in patients with bronchiolitis obliterans syndrome (BOS) after lung transplantation (LTX), which is a disorder in which predominantly small airways obstruction causes progressive airflow limitation.


METHODS
The FVC/SVC ratio was analyzed both cross-sectionally and longitudinally in 39 patients (26 men) with BOS after bilateral LTX (median age, 47 years; interquartile range [IQR], 35 to 54 years), and 36 bilateral lung transplant recipients without BOS (14 men; median age, 46 years; IQR, 41 to 53 years).


RESULTS
The FVC/SVC ratio decreased significantly during follow-up in patients with BOS stages 1 and 2, by 2.2% and 4.4%, respectively, from baseline (p < 0.001). This decrease was not significantly associated with the decrease in FEV(1). The FVC/SVC ratio increased, though not significantly, in the group in which BOS did not develop by 1.1%, which is a significant difference from the average fall of 4.4% in the group in which BOS developed.


CONCLUSIONS
Significant, yet small decreases in FVC/SVC ratio occur in patients in whom BOS develops, independent from changes in FEV(1). At a group level, FVC/SVC ratio is able to detect small airways changes. These results merit prospective studies to determine the sensitivity of FVC/SVC ratio to quantifying small airways dysfunction at an individual level and in other airway diseases.
Cohen
Judith
J
Department of Pulmonology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
Postma
Dirkje S
DS
Vink-Klooster
Karin
K
van der Bij
Wim
W
Verschuuren
Erik
E
Ten Hacken
Nick H T
NH
Koëter
Gerard H
GH
Douma
W Rob
WR
D000328:Adult; D000402:Airway Obstruction / Q000175:diagnosis* / Q000503:physiopathology; D001989:Bronchiolitis Obliterans / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D006801:Humans; D007320:Inspiratory Capacity / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013147:Spirometry; D014797:Vital Capacity / Q000502:physiology*