title: Respiratory mechanics in patients ventilated for critical lung disease.
abstract: Respiratory mechanics, using flow interruption, was previously studied during the complete breath in healthy ventilated man, numerical techniques relieving constraints regarding flow pattern. The classical linear model of non-Newtonian behaviour was found to be valid. The present study was extended to subjects with critical lung disease. Subjects with acute lung injury (ALI; n = 2), acute respiratory distress syndrome (ARDS; n = 4), and chronic obstructive pulmonary disease (COPD; n = 3) were studied with and without positive end-expiratory pressure (PEEP). Functional residual capacity (FRC) was measured with sulphur hexafluoride (SF6) wash-out. The static pressure-volume (P-V) curve was linear at zero end-expiratory pressure (ZEEP), but nonlinear at PEEP. Its hysteresis was nonsignificant. In ALI/ARDS, PEEP increased lung volume by distension and recruitment, but only by distension in COPD. In ALI/ARDS, resistance was increased, at ZEEP. In COPD, resistance became extremely high during expiration at ZEEP. In ALI/ARDS at ZEEP, non-Newtonian behaviour, representing tissue stress relaxation and pendel-luft, complied with the classical linear model. At PEEP, the non-Newtonian compliance became volume-dependent to an extent correlated to the nonlinearity of the static P-V curve. In COPD, non-Newtonian behaviour was adequately explained only with a model with different inspiratory and expiratory behaviour. The classical model of the respiratory system is valid in ALI/ARDS at ZEEP. More advanced models are needed at PEEP and in COPD.
authors.affiliation: Medical Unit, INSERM U296, Hôpital H. Mondor, Créteil, France.
authors.forename: L
authors.initials: L
authors.lastname: Beydon
authors.forename: C
authors.initials: C
authors.lastname: Svantesson
authors.forename: K
authors.initials: K
authors.lastname: Brauer
authors.forename: F
authors.initials: F
authors.lastname: Lemaire
authors.forename: B
authors.initials: B
authors.lastname: Jonson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005652:Functional Residual Capacity; D006801:Humans; D007231:Infant, Newborn; D008168:Lung / Q000503:physiopathology; D008173:Lung Diseases, Obstructive / Q000503:physiopathology* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D012121:Respiration, Artificial; D012128:Respiratory Distress Syndrome / Q000503:physiopathology* / Q000628:therapy; D012127:Respiratory Distress Syndrome, Newborn / Q000503:physiopathology* / Q000628:therapy; D015656:Respiratory Mechanics / Q000502:physiology*; D012143:Respiratory Physiological Phenomena