Objectives
==========

To investigate the effects of PEEP application during partial liquid ventilation (PLV) on gas exchange and lung mechanics in an animal model of ARF.

Design
======

Prospective, randomized study

Setting
=======

University research laboratory

Subjects
========

Six piglets weighing 7 to 12 kg

Interventions
=============

After induction of anesthesia, tracheostomy and controlled mechanical ventilation animals were instrumented with two central venous catheters, a pulmonary artery and two arterial catheters, and an ultrasonic flow probe around the pulmonary artery. Acute respiratory failure was induced by the infusion of oleic acid (0.08 ml/kg) and repeated lung lavages with 0.9% Nacl (20 ml/kg), the protocol consisted of 4 different PEEP levels (PEEP 0, 5, 10 and 15 cmH~2~O) randomly applied during PLV. The oxygenated and warmed PFC liquid (30 ml/kg) was instilled into the trachea over 5 min without changing the ventilator settings.

Measurements and results
========================

Airway presures, tidal volumes, respiratory compliance, airway resistance and arterial blood gases were measured. Data were obtained at baseline and after lung injury and at each PEEP level during PLV. Data analysis: 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 combined with 2--5 lung lavage induced a significant reduction of PaO~2~/FiO~2~ from 485 ± 28 torr to 68 ± 3.2 torr (*P* \< 0.01) and of Cstat from 1.3 ± 0.06 to 0.67 ± 0.04 ml/cmH~2~O/kg (*P* \< 0.01).

Conclusions
===========

Partial liquid ventilation is a useful technique to improve oxygenation in severe ARDS. The application of PEEP during PLV further improves oxygenation and lung mechanics.

###### 

Blood gases and respiratory variables during PLV with different PEEP levels

                         BL                  ALI           PEEP-0           PEEP-5           PEEP-10          PEEP-15
  ---------------------- ------------------- ------------- ---------------- ---------------- ---------------- ----------------
  PaO~2~/FiO~2~ (torr)      485 ± 28^\*\*^   68 ± 3        269 ± 49^\*\*^   274 ± 53^\*\*^   320 ± 50^\*\*^   401 ± 46^\*\*^
  Qs/Qt(%)               20.5 ± 5^\*\*^      48 ± 3        33 ± 3^\*\*^     33 ± 3^\*\*^     30 ± 2^\*\*^     24 ± 2^\*\*^
  pH                     7.39 ± 0.01         7.28 ± 0.02   7.26 ± 0.03      7.26 ± 0.03      7.27 ± 0.04      7.29 ± 0.1
  PaCO~2~ (torr)         42 ± 2              44 ± 4        47 ± 5           48 ± 5           47 ± 6           45 ± 5
  PIP (cmH~2~O)          26.1 ± 1^\*\*^      38.5 ± 2.4    52.6 ± 1.6^\*^   43 ± 2.4^\*^     35 ± 0.8         39.5 ± 0.9
  Pplat(crnH~2~O)        17.1 ± 1^\*\*^      31.6 ± 2.3    25.6 ± 1.7^\*^   25.6 ± 1.4^\*^   27.3 ± 1.1^\*^   32.6 ± 1.2
  Paw (cmH~2~O)          9.3 ± 0.2^\*\*^     14.1 ± 0.47   12.8 ± 0.3       14 ± 0.2^\*\*^   17 ± 0.2^\*^     21.5 ± 0.2^\*^
  Cstat^†^               1.3 ± 0.1^\*\*^     0.67 ± 0.04   0.71 ± 0.04      0.82 ± 0.1^\*^   0.95 ± 0.1^\*^   0.94 ± 0.1^\*^
  Rawm^††^               20 ± 3.9^\*^        25.5 ± 4.4    30.6 ± 4.6^\*^   26.5 ± 3.1       21.1 ± 3.4       21 ± 4.1

^\*^*P* \< 0.05 vs ALI, ^\*\*^*P* \< 0.01 vs ALI, BL: baseline; ALI: Acute Lung Injury; ^†^ml/cmH~2~O/kg, ^††^cmH~2~O/l/s

Acknowledgement
===============

The work was supported by grants of the Austrian Nationalbank Nr:6496
