title: Pressure-release tracheal gas insufflation reduces airway pressures in lung-injured sheep maintaining eucapnia.
abstract: Although tracheal gas insufflation (TGI) has proved to be a useful adjunct to mechanical ventilation, end-inspiratory as well as end-expiratory pressures may increase. We investigated the ability of continuous-flow TGI to maintain eucapnia while reducing airway pressure (Paw) and tidal volume (VT). Seven sheep (36 +/- 2 kg) were ventilated using the Dräger Evita 4 in the pressure control plus mode where flow is released via the expiratory valve to maintain constant inspiratory pressure. To avoid TGI-generated positive end-expiratory pressure (PEEP), a prototype reverse flow TGI tube was used. Two TGI flows (5 and 10 L/min) were investigated pre- and postsaline lavage-induced lung injury. Inspiratory pressures and VT were significantly reduced as TGI flow increased. At 10 L/min TGI flow the carinal pressures (Pcar) and VT were reduced pre- and postinjury by 15% and 20%, and by 28% and 34%, respectively. Tidal volume to dead space ratio (VD/VT) decreased preinjury from 0.49 +/- 0.1 to 0.18 +/- 0.2 and postinjury from 0.62 +/- 0.1 to 0.33 +/- 0.1 at a TGI flow of 10 L/min. The combination of the reverse flow TGI tube and a ventilator with an inspiratory pressure relief mechanism kept set end-inspiratory and end-expiratory pressures constant. This TGI system effectively reduced set Paw and VT while maintaining eucapnia.
authors.affiliation: Respiratory Care Department Laboratory, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: M
authors.initials: M
authors.lastname: Kirmse
authors.forename: Y
authors.initials: Y
authors.lastname: Fujino
authors.forename: J
authors.initials: J
authors.lastname: Hromi
authors.forename: H
authors.initials: H
authors.lastname: Mang
authors.forename: D
authors.initials: D
authors.lastname: Hess
authors.forename: R M
authors.initials: RM
authors.lastname: Kacmarek
mesh_terms: D000403:Airway Resistance; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood*; D006439:Hemodynamics; D007327:Insufflation; D011312:Pressure; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000097:blood / Q000503:physiopathology* / Q000628:therapy; D012756:Sheep; D013990:Tidal Volume; D014132:Trachea
chemical_list: D002245:Carbon Dioxide