Inspiratory tidal volume sparing effects of tracheal gas insufflation in dogs with oleic acid-induced lung injury.
OBJECTIVE
Tracheal gas insufflation (TGI) improves the efficiency of conventional mechanical ventilation (CMV) by reducing the series dead space of the airways. Consequently, application of TGI as an adjunct to CMV may permit reducing tidal volume (VT) while limiting CO2 retention. We tested the extent to which panexpiratory TGI allows reduction of VT while maintaining PaCO2 constant in an oleic acid-induced lung injury model.


METHODS
We studied six anesthetized, paralyzed, and mechanically ventilated dogs. Oleic acid injury was induced by injecting 0.09 mL/kg of oleic acid into the right atrium. After stabilization of lung injury the VT-sparing effect of TGI was tested by progressively increasing catheter flow rate (Vc) from 2 to 5, 10, and 15 L/min while decreasing VT by an amount that maintained PaCO2 constant (approximately 47 mm Hg) with respect to baseline (Vc = 0 L/min).


RESULTS
Tidal volume was decreased from a baseline value of 0.360 +/- 0.030 L to 0.238 +/- 0.054 L at Vc of 15 L/min. The reduction in VT was associated with a decrement in peak and end-inspiratory plateau airway opening pressure from 32 +/- 3 to 28 +/- 6 cm H2O and from 25 +/- 2 to 21 +/- 3 cm H2O, respectively. Total physiological dead space fraction decreased from a baseline value of 0.60 +/- 0.08 to 0.31 +/- 0.20 during TGI at 15 L/min. TGI did not affect cardiac output, PaO2, or pulmonary venous admixture.


CONCLUSIONS
We conclude that TGI can be a useful adjunct to CMV during acute lung injury to limit VT while avoiding CO2 retention.
D000704:Analysis of Variance; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D004195:Disease Models, Animal; D004285:Dogs; D006439:Hemodynamics; D007327:Insufflation; D007442:Intubation, Intratracheal; D055370:Lung Injury; D009829:Oleic Acids; D011650:Pulmonary Alveoli / Q000502:physiology; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation; D012121:Respiration, Artificial / Q000379:methods*; D012126:Respiratory Dead Space; D013990:Tidal Volume; D014947:Wounds and Injuries / Q000139:chemically induced
D009829:Oleic Acids; D002245:Carbon Dioxide