Laboratory Investigation Of Therapeutic Effects During Inhaling Aerosolized And Vaporized Perfluorocarbon In An Piglet Model Of Acute Respiratory Distress Syndrom

In this study, therapeutic effect of aerosolized and vaporized perfluorocarbon (PFC) on pulmonary gas exchange, lung mechanics and hemodynamics was studied in an piglet model of acute respiratory distress syndrome (ARDS) induced by hexadecanoic sulfosuccinate sodium (detergent) infusing through tracheal intubation.Part 1.Twenty-four piglets were randomly assigned to three groups, (1) Aerosol-PFC group, (2) Aerosol-Control group and (3) PEEP-Control group. After successful anaesthesia, tracheal intubation and conventional mechanical ventilation (CMV, VT:8ml/kg, f:40/min, FiO₂:1.0,1:E 1:1) were performed. When common conditions were stable, animal model of ARDS was induced by detergent infusing through tracheal intubation. After permanent model of ARDS established, group (1) received 2 hours CMV (pressure control, P_IP:22cmH₂O, f:40/min, FiO₂:1.0) and aerosolized PFC inhaling by aerosol instrument through tracheal intubation, group (2) received 2 hours CMV (pressure control, parameters the same as group (1)) and aerosol flow (100%O₂) inhaling by the same aerosol instrument without PFC, group (3) received 2 hours CMV (volume control, Vt:8ml/kg, f:40/min, FiO₂:1.0) with 8cmH₂O positive end-expiratory pressure (PEEP).Blood gas analysis, lung mechanic (peak inspiratory pressure Pip, expiratory tidal volume Vte, plateau pressure Ppl, static compliance Cst and auto PEEP) and hemodynamic parameters (mean artery pressure MAP, heart rate HR) were obtained at the moment of baseline, ARDS animal model succeed and every 15-min intervals during 2 hours therapy. As the results shown, at the moment ARDS animal model was established, blood gas and lung mechanic parameters got worse obviously. During 2 hours therapy, blood gas, lung compliance and expiratory tidal volume were improved significantly in group (1). Though there was a slight improvement of these parameters in group (2) and group 3), there was a significant difference among, this 3 groups (P<0.05, repeated measures ANOVA, SPSS 10.0 statistical analytic software). But there was no significant difference of Cst and Vte between group (1) and group (2). This might because that lung overexpandation masked the difference between this two groups, which caused by a continuous high aerosol flow (1.4L/min) existing in this two groups during therapy. In addition, Ppl and PEEPi were significantly higher in group (1) and (2) than in group (3) (P<0.05). The main reason was also the continuous high aerosol flow existing in this two groups during therapy. There was no significant difference of hemodynamic parameters among this three groups (P>0.05).Part 2.16 piglets were randomly assigned to 2 groups, (1) Vaporized-PFC group, (2) CMV-Control group. After successful anaesthesia, tracheal intubation and CMV (volume control, Vt 8ml/kg, f 30/min, FiO₂ 0.6, I:E 1:1) were performed. When common conditions were stable, animal model of ARDS was induced by detergent infusing through tracheal intubation. After a stable animal model of ARDS established, group (1) received 2 hours CMV and vaporized PFC inhaling through a humidifier, and CMV continued 6 hours after therapy, group (2) received 8 hours CMV. Blood gasanalysis, lung mechanic (Pip, Ppl, Vje, Cst) and hemodynamic (MAP, HR) parameters were obtained at the moment of baseline, ARDS animal model succeed and 15-min intervals during 2 hours therapy and 30-min intervals during 6 hours post-therapy period. As the results shown, at the moment ARDS animal model was established, all parameters got worse obviously. During 2 hours therapy, pulmonary gas exchange and lung compliance were improved significantly in group (1), and the improvement was sustained the last 6 hours. Especially the oxygenation index improvement reached its maximum at 5th⁶th hour during the post-therapy period. After 8 hours CMV, though there was a slight improvement of these parameters in group (2), the difference of these parameters between this two groups was significant (P<0.05). There was a significant difference of hemodynamic parameters between this two groups (P<0.05)This investigation demonstrated the therapeutic effect of aerosolized and vaporized PFC inhaling in ARDS piglet. Though aerosolized PFC inhaling can improve oxygenation and lung compliance of ARDS piglet, the existence of high aerosol flow produced a high plateau pressure and a large tidal volume that will aggravate lung injury. So this method and the aerosol instruments need further improvement to avoid this problem. Vaporized PFC inhaling can reach the same effect. The improvement can be sustained 6 hours and reach top of the effect at S*^* hour after therapy. Compared with aerosolized PFC inhaling, this method needs no more special equipment than a humidifier. Therefore it has a better perspective for clinical application.In a word, aerosolized and vaporized PFC inhaling are exciting alternative techniques of partial liquid ventilation (PLV), which needs lung perfusion with PFC. The quantity of PFC persisted in the lung is so little (3ml/kg) that the therapeutic effect of this two methods could not be attributed to liquid PEEP effect which exists in PLV. The real mechanism is...