Low bias flow oscillation with heliox in oleic acid-induced lung injury.
OBJECTIVE
To evaluate Co(2) clearance in oleic acid-induced lung injury in rabbits receiving high-frequency oscillatory ventilation with helium-oxygen mixtures through a low bias flow oscillation system designed to conserve expensive gases.


METHODS
A prospective, controlled, interventional, in vivo animal laboratory study.


METHODS
Research laboratory of a health sciences university.


METHODS
Eight New Zealand White Rabbits.


METHODS
Lung injury (Pao(2)/Fio(2) of <250) was induced by intravenous infusion of oleic acid. Low bias flow oscillation was performed with a modified high-frequency oscillatory ventilation circuit that uses low bias flow (100 mL/kg/min) and a soda lime canister to clear CO(2). Low bias flow oscillation-heliox trials were performed with 40%, 50%, 60%, and 70% helium (balanced with oxygen) for 20 mins. Each heliox trial was preceded by a 20-min paired control trial with 40% oxygen/60% nitrogen.


RESULTS
Helium concentrations of 40%, 50%, 60%, and 70% decreased Paco(2) by 13% (47 +/- 7 to 41 +/- 8 torr), 17% (50 +/- 7 to 41 +/- 6 torr), 22% (49 +/- 5 to 38 +/- 7 torr), and 26% (48 +/- 7 to 35 +/- 9 torr), respectively. The gradient between partial pressure of alveolar oxygen and Pao(2) was not affected by 60% helium; however, absolute Pao(2) increased by 15%. Fluid and inotropic requirements were similar in both control and heliox low bias flow oscillation trials.


CONCLUSIONS
Helium concentrations greater than 40% increase Co(2) clearance from oleic acid-injured lungs of rabbits during low bias flow oscillation. The low bias flow oscillation system makes this possible using 1% of the gas volume required during high-frequency oscillatory ventilation.
Siddappa
Rajashekhar
R
Division of Pediatric Critical Care, The Women and Children's Hospital of Buffalo, State University of New York at Buffalo, USA.
Dowhy
Mark S
MS
Rotta
Alexandre T
AT
Hernan
Lynn J
LJ
Fuhrman
Bradley P
BP
D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism*; D006371:Helium / Q000494:pharmacology*; D006612:High-Frequency Ventilation / Q000295:instrumentation / Q000379:methods*; D006935:Hypercapnia / Q000503:physiopathology; D000860:Hypoxia / Q000503:physiopathology; D007262:Infusions, Intravenous; D008168:Lung / Q000378:metabolism*; D055370:Lung Injury; D019301:Oleic Acid / Q000009:adverse effects; D010100:Oxygen / Q000494:pharmacology*; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange / Q000187:drug effects*; D011817:Rabbits; D014947:Wounds and Injuries / Q000139:chemically induced
D002245:Carbon Dioxide; D006371:Helium; D019301:Oleic Acid; C038949:heliox; D010100:Oxygen