TY - JOUR
T1 - Detection of expiratory flow limitation in COPD using the forced oscillation technique
AU - Dellacà, R. L.
AU - Santus, P.
AU - Aliverti, A.
AU - Stevenson, N.
AU - Centanni, S.
AU - Macklem, P. T.
AU - Pedotti, A.
AU - Calverley, P. M A
PY - 2004/2
Y1 - 2004/2
N2 - Expiratory flow limitation (EFL) during tidal breathing is a major determinant of dynamic hyperinflation and exercise limitation in chronic obstructive pulmonary disease (COPD). Current methods of detecting this are either invasive or unsuited to following changes breath-by-breath. It was hypothesised that tidal flow limitation would substantially reduce the total respiratory system reactance (Xrs) during expiration, and that this reduction could be used to reliably detect if EFL was present. To test this, 5-Hz forced oscillations were applied at the mouth in seven healthy subjects and 15 COPD patients (mean±SD forced expiratory volume in one second was 36.8±11.5 % predicted) during quiet breathing. COPD breaths were analysed (n=206) and classified as flow-limited if flow decreased as alveolar pressure increased, indeterminate if flow decreased at constant alveolar pressure, or nonflow-limited. Of these, 85 breaths were flow-limited, 80 were not and 41 were indeterminate. Among other indices, mean inspiratory minus mean expiratory Xrs (ΔXrs) and minimum expiratory Xrs (Xexp,min) identified flow-limited breaths with 100% specificity and sensitivity using a threshold between 2.53-3.12 cmH2O·s·L-1 (ΔXrs) and -7.38- -6.76 cmH2O·s·L-1 (Xexp,min) representing 6.0% and 3.9% of the total range of values respectively. No flow-limited breaths were seen in the normal subjects by either method. Within-breath respiratory system reactance provides an accurate, reliable and noninvasive technique to detect expiratory flow limitation in patients with chronic obstructive pulmonary disease.
AB - Expiratory flow limitation (EFL) during tidal breathing is a major determinant of dynamic hyperinflation and exercise limitation in chronic obstructive pulmonary disease (COPD). Current methods of detecting this are either invasive or unsuited to following changes breath-by-breath. It was hypothesised that tidal flow limitation would substantially reduce the total respiratory system reactance (Xrs) during expiration, and that this reduction could be used to reliably detect if EFL was present. To test this, 5-Hz forced oscillations were applied at the mouth in seven healthy subjects and 15 COPD patients (mean±SD forced expiratory volume in one second was 36.8±11.5 % predicted) during quiet breathing. COPD breaths were analysed (n=206) and classified as flow-limited if flow decreased as alveolar pressure increased, indeterminate if flow decreased at constant alveolar pressure, or nonflow-limited. Of these, 85 breaths were flow-limited, 80 were not and 41 were indeterminate. Among other indices, mean inspiratory minus mean expiratory Xrs (ΔXrs) and minimum expiratory Xrs (Xexp,min) identified flow-limited breaths with 100% specificity and sensitivity using a threshold between 2.53-3.12 cmH2O·s·L-1 (ΔXrs) and -7.38- -6.76 cmH2O·s·L-1 (Xexp,min) representing 6.0% and 3.9% of the total range of values respectively. No flow-limited breaths were seen in the normal subjects by either method. Within-breath respiratory system reactance provides an accurate, reliable and noninvasive technique to detect expiratory flow limitation in patients with chronic obstructive pulmonary disease.
KW - Chronic obstructive pulmonary disease
KW - Forced oscillation technique
KW - Impedance
KW - Respiratory reactance
KW - Within-breath reactance
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U2 - 10.1183/09031936.04.00046804
DO - 10.1183/09031936.04.00046804
M3 - Article
C2 - 14979497
AN - SCOPUS:1042304258
VL - 23
SP - 232
EP - 240
JO - European Journal of Respiratory Diseases
JF - European Journal of Respiratory Diseases
SN - 0903-1936
IS - 2
ER -