title: Driving pressure during assisted mechanical ventilation: Is it controlled by patient brain?
abstract: Tidal volume (VT) is the controlled variable during passive mechanical ventilation (CMV) in order to avoid ventilator-induced-lung-injury. However, recent data indicate that the driving pressure [ΔP; VT to respiratory system compliance (Crs) ratio] is the parameter that best stratifies the risk of death. In order to study which variable (VT or ΔP) is controlled by critically ill patients, 108 previously studied patients were assigned to receive PAV+ (a mode that estimates Crs and permits the patients to select their own breathing pattern) after CMV, were re-analyzed. When patients were switched from CMV to PAV+ they controlled ΔP without constraining VT to narrow limits. VT was increased when the resumption of spontaneous breathing was associated with an increase in Crs. When ΔP was high during CMV, the patients (n=12) decreased it in 58 out of 67 measurements. We conclude that critically ill patients control the driving pressure by sizing the tidal volume to individual respiratory system compliance using appropriate feedback mechanisms aimed at limiting the degree of lung stress.
authors.affiliation: Intensive Care Medicine, University Hospital of Heraklion, Medical School, University of Crete, Heraklion, Crete, Greece; Pulmonary Department, University Hospital of Heraklion, Medical School, University of Crete, Heraklion, Crete, Greece. Electronic address: georgop@med.uoc.gr.
authors.forename: Dimitris
authors.initials: D
authors.lastname: Georgopoulos
authors.affiliation: Intensive Care Medicine, University Hospital of Heraklion, Medical School, University of Crete, Heraklion, Crete, Greece.
authors.forename: Nectaria
authors.initials: N
authors.lastname: Xirouchaki
authors.affiliation: Pulmonary Department, University Hospital of Heraklion, Medical School, University of Crete, Heraklion, Crete, Greece.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Tzanakis
authors.affiliation: Sleep Disorders Centre, Misericordia Health Centre, Winnipeg, Manitoba, Canada.
authors.forename: Magdy
authors.initials: M
authors.lastname: Younes
mesh_terms: D001921:Brain / Q000503:physiopathology*; D016638:Critical Illness; D006801:Humans; D059725:Interactive Ventilatory Support; D008168:Lung; D008170:Lung Compliance; D011312:Pressure; D012018:Reflex / Q000502:physiology*; D012119:Respiration; D013990:Tidal Volume; D055397:Ventilator-Induced Lung Injury / Q000503:physiopathology / Q000517:prevention & control
keywords: Chemical feedback; Proportional assist ventilation; Reflex feedback; Respiratory system compliance; Tidal volume