Objective TLV is an effective strategy in ARDS. However, cardiovascular influence of TLV is still controversial. This study evaluates efficacy, and cardiovascular influence of TLV in a controlled animal trial.
Methods 17 anesthetised-paralysed gas-ventilated newborn-lambs instrumented for monitoring of systemic and pulmonary cardiovascular parameters using thermodilution technique (PC-8000-PICCO-VOLEF monitor, Pulsion-Medical-System.ge). Lung injury established using Hcl saline lavages. Post-injury, animals randomised into 3 groups: 1) GV = 6; who remained GV in PRVC (Fr = 60/min, Vt = 10±1 ml.kg, PiP = 20–25 cm.H2O, Peep = 9±1 cm H2O, FiO2 = 1.0); 2) TLV = 11, with lungs filled with either 25 ml/kg perfuorooctylbromide (PFOB, n = 5) or perfluorodecalin (PFDEC, n = 6) (F2-chemicals, UK) and ventilated with volume-controlled-pressure-limited-liquid ventilator (INOLIVENT) (Fr = 3–5/min, Vt = 20 ml/kg, FiO = 1.0). Mean arterial pressure (MAP) were maintained using crystalloid volumes and vasopressors. Gas exchanges, Lactate/Pyruvate ratio (L/P) and cardiovascular parameters were recorded (30 min intervals) for 240 min.
Results Mean PaO2, PaCO2 and pH were similar in all groups and maintained in the targeted range at a significant low mean airway pressure during TLV. Mean systemic and pulmonary cardiovascular parameters were similar in all groups. As compared to post-injury value a transient but significant decrease in MAP was observed in the TLV groups, with no difference in L/P, however. This could be the result of a significant increase in intrathoracic pressure combined with a decrease in the sympathic autonomic system reactivity due to anesthesia. No significant differences could be demonstrated between the two PFC tested.
Conclusion 1) TLV can maintain physiologic gas exchanges without significant cardiovascular effects; 2) Despite a different biophysical profile, PFDEC is as effective as PFOB.