Time-dependency of improvements in arterial oxygenation during partial liquid ventilation in experimental acute respiratory distress syndrome

Abstract

) due to PLV in eight pigs with experimental lung injury, in order to discriminate increases due to oxygen dissolved in perfluorocarbon before its intrapulmonary instillation from a persistent diffusion of the respiratory gas through the liquid column. for doses that approximated the functional residual capacity of the animals. .

Background:

) due to PLV in eight pigs with experimental lung injury, in order to discriminate increases due to oxygen dissolved in perfluorocarbon before its intrapulmonary instillation from a persistent diffusion of the respiratory gas through the liquid column.

Results:

for doses that approximated the functional residual capacity of the animals.

Conclusion:

.

Introduction

]. Additionally, the high solubility of oxygen and carbon dioxide in perfluorocarbons (40-60 and 160-210 ml/100ml, respectively) suggests a potential role for these substances as transport media for the respiratory gases in nonventilated but perfluorocarbon-filled, dependent lung segments, depending on the diffusion of oxygen and carbon dioxide through the liquid. A persistent effect on pulmonary gas exchange requires an efficient transfer of oxygen from the inspired gas to the perfluorocarbon and through the liquid column to the alveoli. Oxygen dissolved in perfluorocarbon before the intrapulmonary instillation of the compound, however, may cause only a short-lasting improvement in arterial oxygenation after the onset of PLV.

in this setting, suggesting a minor role of oxygen transfer through perfluorocarbon in the improvement of gas exchange observed during PLV.

Animal preparation

The experimental protocol was approved by the appropriate governmental institution and the study was performed according to the Helsinki convention for the use and care of animals.

O and an inspiration:expiration ratio of 1:2 without pause time. The ventilator setting remained unchanged during the study.

A 18 G arterial line (Vygon, Ecouen, France) and a 8.5 Fr venous sheath (Arrow Deutschland GmbH, Erding, Germany) for positioning of a right heart catheter (model 93A-431-7.5 F; Baxter Healthcare Corporation, Irvine, CA, USA) under transduced pressure guidance were percutaneously inserted into the femoral vessels.

The blood temperature, determined by means of the pulmonary artery catheter, was maintained at 37.2 ± 1.1°C during the experiment using an infrared warming lamp and a warming pad. A continuous infusion of 4-5 ml/kg per min of a balanced electrolyte solution was administered for adequate hydration.

Data acquisition

All haemodynamic measurements were taken in the supine position with zero reference level at the midchest. Central venous pressure, mean arterial pressure, mean pulmonary arterial pressure and pulmonary artery occlusion pressure of all animals were transduced (Baxter Deutschland GmbH, Unterschleißheim, Germany) and recorded (Hewlett-Packard Model 66 S monitor; Böblingen, Germany). Cardiac output was determined using standard thermodilution techniques (Baxter Deutschland GmbH) and expressed as the mean of three measurements at end-expiration of different respiratory cycles. Heart rate was taken from the blood pressure curve.

Arterial and mixed venous blood samples were collected anaerobically and immediately analyzed for partial oxygen tension, partial carbon dioxide tension and pH using standard blood gas electrodes (ABL 520; Radiometer, Copenhagen, Denmark). Species-specific spectrophotometry was performed to obtain arterial and mixed venous oxygen saturation and total haemoglobin concentration (OSM 3 Hemoximeter; Radiometer).

).

Experimental protocol

, it has a viscosity of 0.7 centistokes, a vapour pressure of 61 torr and a surface tension of 12 mN/m at 25°C, and it can dissolve up to 40 ml oxygen/100ml perfluorocarbon and 192 ml carbon dioxide/100 ml perfluorocarbon.

All haemodynamic and gas exchange parameters were determined 5 and 30 min after starting the instillation of each dose of perfluorocarbon. At the end of the study, all animals were killed with an intravenous application of potassium chloride.

Statistical analyses

< 0.05 was considered statistically significant.

Gas exchange

).

Haemodynamics

< 0.001) after the onset of ALI and remained unchanged thereafter.

< 0.05 versus values after 5 min with the same dose of perfluorocarbon.

Gas exchange data

, mixed venous oxygen saturation; PLV, partial liquid ventilation.

Gas exchange, peak airway pressure and metabolic data

, arterial carbon dioxide tension; PLV, partial liquid ventilation.

Haemodynamic data

Values are expressed as mean ± standard deviation. ALI, acute lung injury; CVP, central venous pressure; MAP, mean arterial pressure; MPAP, mean pulmonary arterial pressure; PAOP, pulmonary artery occlusion pressure; PLV, partial liquid ventilation.

Discussion

values achieved immediately after instillation of the liquid. Additionally, the continuous administration of perfluorocarbon in order to substitute for evaporational losses can avoid a decrease in the total volume of perfluorocarbon in the lung, but there may be a significant difference in the distribution of the liquid when compared with the application of a bolus. Evaporation is likely to be increased in lung units reconducted to gaseous ventilation after recruitment due to the surfactant-like activity of perfluorocarbon. If the evaporational loss of perfluorocarbon in these units can not be substituted due to their localization, the alveoli may destabilize again and recurrent atelectasis may occur, resulting in a time-dependent decrease in arterial oxygenation.

] also reported a wide range of individual responses. The reason for this lack of effect remains speculative, but it may be assumed that different degrees and causes of lung injury determining ventilation may account for this observation.

] who found a dose-dependent increase in pulmonary shunt during PLV in healthy piglets using the multiple inert gas elimination technique. They suggest that, apart from pure shunt, these results are due to a diffusion limitation of oxygen and carbon dioxide in lungs partly filled with perfluorocarbon.

These uncertainties need to be addressed in future studies investigating the ventilation:perfusion ratio and the diffusion of gases through the liquid perfluorocarbons, in order to understand better the mechanisms by which PLV can improve gas exchange and to elucidate the relevance of the compound as a transfer medium for oxygen and carbon dioxide during PLV.

Keywords

• acute lung injury
• partial liquid ventilation
• perfluorocarbon