Minimal redistribution of regional ventilation-perfusion ratios by 10 and 20 cmH2O positive end-expiratory pressure in prone sheep
2014 (English)Manuscript (preprint) (Other academic)
Positive end-expiratory pressure (PEEP) has posture dependent effects on the distributions of ventilation (V) and perfusion (Q). We examined if redistribution of regional ventilation-perfusion ratios (V/Q) by PEEP was identical in prone and supine.
Mechanically ventilated sheep (n=16) were studied in prone or supine with 0, 10 and 20 cmH2O PEEP. V and Q were measured with a fluorescent microsphere aerosol and an intravenous infusion of microspheres, respectively. The right lung was dried at total lung capacity and diced into approx. 1000 regions tracking the spatial location of each region.
In prone V/Q was close to unity in all horizontal planes with 0 PEEP and remained so with 10 and 20 PEEP. In supine V/Q was imperfect in the most dependent planes with 0 and 10 PEEP. V/Q approached unity in these planes when 20 PEEP was applied, but V/Q in non-dependent planes increased. The slope of the linear relationship between vertical height and V/Q was not different from zero at any PEEP in prone, but was larger than zero with all PEEP levels in supine. Mean V/Q heterogeneity (SDlogV/Q) was lower in prone at all PEEP levels (0 PEEP: 0.22 vs. 0.37, 10 PEEP: 0.21 vs. and 0.32 and 20 PEEP: 0.19 vs. 0.39, P<0.01).
Redistribution of regional V/Q was minimal in prone with PEEP and remained close to ideal in all horizontal planes. The absence of high V/Q with PEEP in prone may be clinically important when recruitment fails in the supine posture.
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IdentifiersURN: urn:nbn:se:liu:diva-112360OAI: oai:DiVA.org:liu-112360DiVA: diva2:765620