title: A single-compartment model cannot describe passive expiration in intubated, paralysed humans.
abstract: The time-course of thoracic volume changes (respiratory inductive plethysmograph) during relaxed expiration was studied in 11 intubated, paralysed, mechanically ventilated subjects. The semilog volume-time curves show that expiration is governed by two apparently separate mechanisms: one causes emptying of most of the expired volume (approximately 80%) with a time constant of 0.50 +/- 0.22 s for a baseline tidal volume of 0.44 +/- 0.12 l (mean +/- SD) and 0.37 +/- 0.14 s when the tidal volume is reduced (VTP); the other contributes a relatively small amount to the expired volume over a significantly longer time, the time constant amounting to 3.27 +/- 1.54 s for baseline VT and 2.95 +/- 1.65 s for VTp. The first mechanism probably reflects the standard elastic and flow resistive properties of the respiratory system, while the second, slower compartment, is probably an expression of the viscoelastic properties of the pulmonary and chest wall tissues.
authors.affiliation: Dipartimento di Fisiopatologia Clinica, Università di Firenze, Italy.
authors.forename: G L
authors.initials: GL
authors.lastname: Chelucci
authors.forename: F
authors.initials: F
authors.lastname: Brunet
authors.forename: J
authors.initials: J
authors.lastname: Dall'Ava-Santucci
authors.forename: J F
authors.initials: JF
authors.lastname: Dhainaut
authors.forename: D
authors.initials: D
authors.lastname: Paccaly
authors.forename: A
authors.initials: A
authors.lastname: Armaganidis
authors.forename: J
authors.initials: J
authors.lastname: Milic-Emili
authors.forename: A
authors.initials: A
authors.lastname: Lockhart
mesh_terms: D000328:Adult; D003128:Coma / Q000503:physiopathology; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal; D008176:Lung Volume Measurements; D008297:Male; D008954:Models, Biological; D010243:Paralysis / Q000503:physiopathology*; D012123:Pulmonary Ventilation / Q000502:physiology; D012119:Respiration / Q000502:physiology*; D012121:Respiration, Artificial; D015656:Respiratory Mechanics / Q000502:physiology; D013406:Suicide, Attempted