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Objectives
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To investigate the effects of two different gas ventilation strategies during partial liquid ventilation (PLV) on gas exchange and lung mechanics in acute lung injury.

Design
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Prospective, randomized, experimental study.

Setting
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University research laboratory.

Subjects
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Fourteen piglets weighing 8.9± 0.2 kg.

Interventions
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Acute lung injury was induced by the infusion of oleic acid and repeated lung lavages with 0.9% NaCl (20 ml/kg). After a stabilization period of 30 min the animals were randomized to two groups with different PEEP levels and tidal volumes (Group A: Vt \>12.5 ml/kg, PEEP 6 cmH~2~O; Group B: Vt 9 ml/kg, PEEP 12 cmH~2~O). The pre-oxygenated and warmed perfluorocarbon liquid (30 ml/kg) was instilled into the trachea over 15 min without changing the ventilator settings.

Measurements and main results
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Airway pressures, tidal volumes, static respiratory compliance, inspiratory and expiratory airway resistances and arterial blood gases were measured. Data were obtained at baseline, after lung injury and at 60 and 120 min of PLV. See Table [1](#T1){ref-type="table"}.

Data analysis
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Values are given as mean ± SEM. Comparisons were made by ANOVA for repeated measures. A *P*-value of \<0.05 was considered significant. The infusion of oleic acid (0.07 ml/kg) combined with five lung lavages induced a significant reduction of PaO~2~/FiO~2~ from 486± 24 torr to 60± 3.8 torr (*P*\<0.01).

Conclusions
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During PLV both gas ventilation strategies significantly improved oxygenation in an animal model of acute lung injury. Static compliance of the respiratory system was not different between both gas ventilation strategies. Inspiratory airway resistance was significantly higher during the low PEEP-high Vt gas ventilation strategy, whereas the high PEEP-low VT strategy resulted in significantly higher PaCO~2~ values.

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Blood gases and respiratory variables during PLV with two different strategies of gas ventilation.

  Parameters             Group   BL                      ALI                   T-60min                              T-120min
  ---------------------- ------- ----------------------- --------------------- ------------------------------------ ------------------------------
  PaO~2~/FiO~2~ (torr)   A          490± 30^\*\*^           62± 6                  228± 50^\*^                      207± 34^\*^
                         B          493± 40^\*\*^               61± 125            230± 56^\*^                      245± 62^\*^
  Qs/Qt(%)               A       14.9± 3^\*\*^              55± 4                  34± 6^\*^                        35± 4^\*^
                         B          14± 2^\*\*^             48± 3                  32± 4^\*^                        31± 4^\*^
  Cstat(ml/cmH~2~O/kg)   A          1.02± 0.1^\*\*^           0.52± 0.05            0.63± 0.08                      0.59± 0.08
                         B            1.05± 0.05^\*\*^        0.43± 0.05            0.52± 0.06                      0.55± 0.07
  Rawinsp(cmH~2~O/L/s)   A            34± 1.7^\*^                43± 5.9^\*^             65± 3.4^\*\*^                  67± 5.8^\*\*^
                         B         38± 4^\*^                     53± 7.2^\*^         44± 5\#                           43± 6.1\#
  Vd/Vt(%)               A           13.7± 3.0^\*\*^        37± 5                  35± 3                             42± 2.7
                         B           11± 3^\*\*^            37± 1                     30± 1.8                          32± 2.5\#
  PaCO~2~ (torr)         A           41.7± 1.5^\*\*^     54.4± 3                       41.7± 2.3^\*\*^                43.8± 1.1^\*\*^
                         B           39.9± 2.9^\*\*^         48.3± 2.2                         64± 2.4^\*\*^ \#\#             66± 2.1^\*\*^ \#\#

Group A: Vt \>12.5 ml/kg, PEEP 6 cmH~2~O, Group B: Vt 9 ml/kg, PEEP 12 cmH~2~O; ^\*^*P*\<0.05 vs ALI, ^\*\*^*P*\<0.01 vs ALI, BL: baseline; ALI: acute lung injury; \#*P*\<0.05 vs group A, \#\#*P*\<0.01 vs group A.
