The Science Journal of the American Association for Respiratory Care

1997 OPEN FORUM Abstracts

THE RESPONSE TO POSITIVE END-EXPIRATORY PRESSURE (PEEP) DURING PARTIAL LIQUID VENTILATION (PLV) IS DOSE DEPENDENT.

Max Kirmse, MD, Yuji Fujino, MD, Dean Hess, PhD, RRT, Robert M Kacmarek, PhD, RRT Respiratory Care & Dept. of Anesthesia and Critical Care, Harvard Medical School, Massachusetts General Hospital, Boston, MA 02114

Partial liquid ventilation (PLV) with perflubron (PFB) has been proposed as an adjunct to the current therapies for the acute respiratory distress syndrome (ARDS). Since PFB has been also referred to as "liquid-PEEP", distributing to the most gravity dependent regions of the lung, less attention has been paid to the amount of applied PEEP. We recently reported, that the lower inflection point (LIP) of a pressure-volume loop shifts to the left with subsequently increasing doses of PFB [1]. We now hypothesized, that PEEP has an additive effect to different doses of PFB, when set above the LIP. Methods: Lung injury was induced by repeated lung lavage with warmed saline in 15 sheep until PaO_{2}/FiO_{2} ratio fell below 150. To evaluate the impact of PEEP set above the LIP at different fill levels of PFB, three groups (n=5) with different doses (7.5 mL-15 mL-30 mL/kg/BW) of PFB were investigated. In random order a PEEP of 5 cm H_{2}O (BELOW) or PEEP above the LIP (ABOVE) was applied. Data for gas exchange, hemodynamics, and airway mechanics were analyzed using a 2-way ANOVA and HSD-post hoc. Results: No significant changes in hemodynamics were observed, data is reported in the table below (C_{stat} = V_{T} / (P_{Plat}-PEEP_{Total})):

Dose Preinjury Injury Below LIP Above LIP

PaO_{2} 7.5 445±95{$} 74±14 68±27 87±66

15 441±102{$} 103±35 152±36 203±68{+}

[mm Hg] 30 425±68{$} 98±40 193±57{+} 298±80{+#$*}

PaCO_{2} 7.5 28±4.1 31.2±5.8 33.8±5.8 34.4±3.3

15 34±4.5 37.4±3.3 37.8±5.4 36.6±5.0

[mm Hg] 30 34±4.7 36.2±3.1 41.2±5.8 36.4±3.6

C_{stat} 7.5 31.7±8.0{$} 14.3±3.2 14.4±2.3 14.5±3.0

[mL/ 15 27.1±5.1{$} 17.2±3.4 20.3±5.0{+} 22.8±5.8{$+}

cm H_{2}O] 30 25.0±2.7{$} 15.6±3.3 17.6±3.5{?} 22.8±3.4{$+*}

Post hoc: within group: $ p < 0.05 vs. Injury; * p < 0.05 vs. Below LIP

across groups: + p < 0.05 vs. all stages, dose 7.5 mL/kg/BW; # p < 0.05 vs. Below LIP, dose 15 mL, ? p < 0.05 vs. Above LIP, dose 15 mL

Conclusion: The response to PEEP above the LIP is dose dependent and improves gas exchange and airway mechanics at moderate to high doses of PFB (>= 15 mL/kg/ body weight)

[1] Fujino Y, Kirmse M, Hess D, Mang H, Kacmarek RM Relationship between fill-volume during partial liquid ventilation and the lower inflection point on a static pressure volume curve. Am. J. Resp. Crit Care 1997;155:A745

OF-97-121

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