RT Journal Article
SR Electronic
T1 Single-breath method for assessing the viscoelastic properties of the respiratory system
JF European Respiratory Journal
JO Eur Respir J
FD European Respiratory Society
SP 1191
OP 1196
DO 10.1183/09031936.98.12051191
VO 12
IS 5
A1 V Antonaglia
A1 A Grop
A1 P Demanins
A1 F Beltrame
A1 U Lucangelo
A1 A Peratoner
A1 L De Simoni
A1 A Gullo
A1 J Milic-Emili
YR 1998
UL http://erj.ersjournals.com/content/12/5/1191.abstract
AB In order to explain the time dependency of resistance and elastance of the respiratory system, a linear viscoelastic model (Maxwell body) has been proposed. In this model the maximal viscoelastic pressure (Pvisc.max) developed within the tissues of the lung and chest wall at the end of a constant-flow (V') inflation of a given time (tI) is given by: Pvisc,max = R2V'(1-e(-tI/tau2), where R2 and tau2 are, respectively, the resistance and time constant of the Maxwell body. After rapid airway occlusion at t1, tracheal pressure (Ptr) decays according to the following function: Ptr(t) = Pvisc(t) + Prs,st = Pvisc,max(etocc/tau2)+ Prs,st, where tocc/is time after occlusion and Prs,st is static re-coil pressure of the respiratory system. By fitting Ptr after occlusion to this equation, tau2 and Pvisc,max are obtained. Using these values, together with the V' and tI pertaining to the constant-flow inflation preceding the occlusion, R2 can be calculated from the former equation. Thus, from a single breath, the constants tau2, R2 and E2 (R2/tau2) can be obtained. This method was used in 10 normal anaesthetized, paralysed, mechanically ventilated subjects and six patients with acute lung injury. The results were reproducible in repeated tests and similar to those obtained from the same subjects and patients with the time-consuming isoflow, multiple-breath method described previously.