title: Pulmonary embolization causes hypoxemia by redistributing regional blood flow without changing ventilation.
abstract: To explore mechanisms of hypoxemia after acute pulmonary embolism, we measured regional pulmonary blood flow and alveolar ventilation before and after embolization with 780-micrometers beads in five anesthetized, mechanically ventilated pigs. Regional ventilation and perfusion were determined in approximately 2.0-cm3 lung volumes by using 1-micrometers-diameter aerosolized and 15-micrometers-diameter injected fluorescent microspheres. Hypoxemia after embolization resulted from increased perfusion to regions with low ventilation-to-perfusion ratios. Embolization caused an increase in perfusion heterogeneity and a fall in the correlation between ventilation and perfusion. Correlation between regional ventilation pre- and postembolization was greater than correlation between regional perfusion pre- and postembolization. The majority of regional ventilation-to-perfusion ratio heterogeneity was attributable to changes in regional perfusion. Regional perfusion redistribution without compensatory changes in regional ventilation is responsible for hypoxemia after pulmonary vascular embolization in pigs.
authors.affiliation: Department of Medicine, University of Washington, Seattle, Washington 98195-6522, USA.
authors.forename: W A
authors.initials: WA
authors.lastname: Altemeier
authors.forename: H T
authors.initials: HT
authors.lastname: Robertson
authors.forename: S
authors.initials: S
authors.lastname: McKinney
authors.forename: R W
authors.initials: RW
authors.lastname: Glenny
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D000860:Hypoxia / Q000209:etiology*; D008297:Male; D011652:Pulmonary Circulation / Q000502:physiology; D011655:Pulmonary Embolism / Q000150:complications* / Q000503:physiopathology*; D012039:Regional Blood Flow / Q000502:physiology; D012119:Respiration; D013552:Swine; D013997:Time Factors; D014692:Ventilation-Perfusion Ratio