Am. J. Respir. Crit. Care Med.,
Volume 160, Number 5, November 1999, 1462-1467
Pressure-release Tracheal Gas Insufflation Reduces
Airway Pressures in Lung-injured Sheep
Maintaining Eucapnia
MAX
KIRMSE,
YUJI
FUJINO,
JONATHAN
HROMI,
HARALD
MANG,
DEAN
HESS,
and
ROBERT M.
KACMAREK
Respiratory Care Department Laboratory and the Department of Anesthesia and Critical Care, Massachusetts General
Hospital and Harvard Medical School, Boston, Massachusetts
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. Kirmse M, Fujino Y, Hromi J, Mang H, Hess D, Kacmarek RM. Pressure-release tracheal gas insufflation reduces airway pressures in lung-injured
sheep maintaining eucapnia.
