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Marked differences between prone and supine sheep in effect of PEEP on perfusion distribution in zone II lung.
J Appl Physiol (1985). 2005 Sep; 99(3):909-14.JA

Abstract

The classic four-zone model of lung blood flow distribution has been questioned. We asked whether the effect of positive end-expiratory pressure (PEEP) is different between the prone and supine position for lung tissue in the same zonal condition. Anesthetized and mechanically ventilated prone (n = 6) and supine (n = 5) sheep were studied at 0, 10, and 20 cm H2O PEEP. Perfusion was measured with intravenous infusion of radiolabeled 15-microm microspheres. The right lung was dried at total lung capacity and diced into pieces (approximately 1.5 cm3), keeping track of the spatial location of each piece. Radioactivity per unit weight was determined and normalized to the mean value for each condition and animal. In the supine posture, perfusion to nondependent lung regions decreased with little relative perfusion in nondependent horizontal lung planes at 10 and 20 cm H2O PEEP. In the prone position, the effect of PEEP was markedly different with substantial perfusion remaining in nondependent lung regions and even increasing in these regions with 20 cm H2O PEEP. Vertical blood flow gradients in zone II lung were large in supine, but surprisingly absent in prone, animals. Isogravitational perfusion heterogeneity was smaller in prone than in supine animals at all PEEP levels. Redistribution of pulmonary perfusion by PEEP ventilation in supine was largely as predicted by the zonal model in marked contrast to the findings in prone. The differences between postures in blood flow distribution within zone II strongly indicate that factors in addition to pulmonary arterial, venous, and alveolar pressure play important roles in determining perfusion distribution in the in situ lung. We suggest that regional variation in lung volume through the effect on vascular resistance is one such factor and that chest wall conformation and thoracic contents determine regional lung volume.

Authors+Show Affiliations

Intensive Care Unit, Div. of Surgery, Ullevål University Hospital, N-0407 Oslo, Norway. sten.walther@telia.comNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15774701

Citation

Walther, Sten M., et al. "Marked Differences Between Prone and Supine Sheep in Effect of PEEP On Perfusion Distribution in Zone II Lung." Journal of Applied Physiology (Bethesda, Md. : 1985), vol. 99, no. 3, 2005, pp. 909-14.
Walther SM, Johansson MJ, Flatebø T, et al. Marked differences between prone and supine sheep in effect of PEEP on perfusion distribution in zone II lung. J Appl Physiol (1985). 2005;99(3):909-14.
Walther, S. M., Johansson, M. J., Flatebø, T., Nicolaysen, A., & Nicolaysen, G. (2005). Marked differences between prone and supine sheep in effect of PEEP on perfusion distribution in zone II lung. Journal of Applied Physiology (Bethesda, Md. : 1985), 99(3), 909-14.
Walther SM, et al. Marked Differences Between Prone and Supine Sheep in Effect of PEEP On Perfusion Distribution in Zone II Lung. J Appl Physiol (1985). 2005;99(3):909-14. PubMed PMID: 15774701.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Marked differences between prone and supine sheep in effect of PEEP on perfusion distribution in zone II lung. AU - Walther,Sten M, AU - Johansson,Mats J, AU - Flatebø,Torun, AU - Nicolaysen,Anne, AU - Nicolaysen,Gunnar, Y1 - 2005/03/17/ PY - 2005/3/19/pubmed PY - 2005/10/28/medline PY - 2005/3/19/entrez SP - 909 EP - 14 JF - Journal of applied physiology (Bethesda, Md. : 1985) JO - J Appl Physiol (1985) VL - 99 IS - 3 N2 - The classic four-zone model of lung blood flow distribution has been questioned. We asked whether the effect of positive end-expiratory pressure (PEEP) is different between the prone and supine position for lung tissue in the same zonal condition. Anesthetized and mechanically ventilated prone (n = 6) and supine (n = 5) sheep were studied at 0, 10, and 20 cm H2O PEEP. Perfusion was measured with intravenous infusion of radiolabeled 15-microm microspheres. The right lung was dried at total lung capacity and diced into pieces (approximately 1.5 cm3), keeping track of the spatial location of each piece. Radioactivity per unit weight was determined and normalized to the mean value for each condition and animal. In the supine posture, perfusion to nondependent lung regions decreased with little relative perfusion in nondependent horizontal lung planes at 10 and 20 cm H2O PEEP. In the prone position, the effect of PEEP was markedly different with substantial perfusion remaining in nondependent lung regions and even increasing in these regions with 20 cm H2O PEEP. Vertical blood flow gradients in zone II lung were large in supine, but surprisingly absent in prone, animals. Isogravitational perfusion heterogeneity was smaller in prone than in supine animals at all PEEP levels. Redistribution of pulmonary perfusion by PEEP ventilation in supine was largely as predicted by the zonal model in marked contrast to the findings in prone. The differences between postures in blood flow distribution within zone II strongly indicate that factors in addition to pulmonary arterial, venous, and alveolar pressure play important roles in determining perfusion distribution in the in situ lung. We suggest that regional variation in lung volume through the effect on vascular resistance is one such factor and that chest wall conformation and thoracic contents determine regional lung volume. SN - 8750-7587 UR - https://www.unboundmedicine.com/medline/citation/15774701/Marked_differences_between_prone_and_supine_sheep_in_effect_of_PEEP_on_perfusion_distribution_in_zone_II_lung_ L2 - https://journals.physiology.org/doi/10.1152/japplphysiol.01388.2004?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -