Partial liquid ventilation in acute salt water-induced lung injury.

BACKGROUND AND OBJECTIVES: Salt-water aspiration results in pulmonary oedema and hypoxia. We tested the hypothesis that partial liquid ventilation has beneficial effects on gas exchange and rate of survival in acute and extended salt water-induced lung injury. METHODS: Anaesthetized, ventilated rats (tidal volume 6 mL kg(-1), PEEP 5 cmH2O) received a tracheal salt-water instillation (3%, 8 mL kg(-1) body weight) and were randomly assigned to three groups (n = 10 per group). While lungs of Group 1 were gas-ventilated, lungs of Group 2 received a single perfluorocarbon instillation (30 min after the injury, 5 mL kg(-1) perfluorocarbon) and lungs of Group 3 received an additional continuous perfluorocarbon application into the treachea (5 mL kg(-1) h(-1)) Arterial blood gases were measured with an intravascular blood gas sensor. RESULTS: Salt-water instillation resulted in a marked decrease in PaO2 values within 30 min (from 432 +/- 65 to 83 +/- 40 mmHg, FiO2 = 1.0, P < 0.01). Arterial oxygenation improved in all three groups irrespective of treatment. We observed no significant differences between groups in peak PaO2 and PaCO2 values. CONCLUSIONS: Our results suggest that partial liquid ventilation has no additional beneficial effects on gas exchange after life-threatening salt water-induced lung injury when compared to conventional gas ventilation with positive end-expiratory pressure.

Continuous intra-arterial blood gas monitoring in rats.

Studies on lung injury and its treatment options are often performed on small animals like rats. Because conventional blood gas analyses may not detect rapid changes in gas exchange during respiratory distress syndrome and intermittent blood withdrawal can result in hypo-volaemia and anaemia, we tested the applicability and accuracy of a continuous intravascular blood gas monitor (Paratrend 7+). Anaesthetized and ventilated rats with a body weight of 398 +/-45 g (n =22) had a 20-gauge cannula inserted in both carotid arteries. A photochemical blood gas sensor for continuous measurement (Paratrend 7+) was advanced into the aorta via the left carotid artery. Blood was sampled for intermittent blood gas analysis by means of the right carotid artery. Arterial pO(2) was varied by applying different inspiratory oxygen concentrations, and arterial pCO(2) by applying different respiratory rates. Paired blood gas measurements (n =136) were analysed over a wide range of pO(2) values (5.3-76.8 kPa). We found an acceptable correlation for pO(2) (r(2)=0.98), pCO(2) (r(2)=0.96) and pH (r(2)=0.92). The calculated bias and imprecision for pO(2) was -1.0 +/- 3.3 kPa, for pCO(2) 0.04 +/- 0.28 kPa and for hydrogen ion concentration -0.05 +/-2.2 nmol/l. We conclude that in rats, continuous blood gas monitoring with a photochemical blood gas sensor provides pO(2), pCO(2) and pH measurements with acceptable accuracy.