Regional lung blood flow and ventilation in upright humans studied with quantitative SPECT.
We used quantitative Single Photon Emission Computed Tomography (SPECT) to study the effect of the upright posture on regional lung blood flow and ventilation. Nine (upright) plus seven (prone and supine) healthy volunteers were studied awake, breathing spontaneously. Regional blood flow and ventilation were marked in sitting upright, supine and prone postures using (113m)In-labeled macroaggregates and inhaled Technegas ((99m)Tc); both remain fixed in the lung after administration. All images were obtained while supine. In comparison with horizontal postures, both blood flow and ventilation were greater in caudal regions when upright. The redistribution was greater for blood flow than for ventilation, resulting in decreasing ventilation-to-perfusion ratios down the lung when upright. We conclude that gravity redistributes regional blood flow and ventilation in the upright posture, while the influence is much less in the supine and prone postures.
Department of Anesthesiology and Intensive Care, Karolinska University Hospital Solna, 171 76 Stockholm, Sweden. johan.petersson@karolinska.se
Johan
J
Petersson
Malin
M
Rohdin
Alejandro
A
Sánchez-Crespo
Sven
S
Nyrén
Hans
H
Jacobsson
Stig A
SA
Larsson
Sten G E
SG
Lindahl
Dag
D
Linnarsson
Blazej
B
Neradilek
Nayak L
NL
Polissar
Robb W
RW
Glenny
Margareta
M
Mure
D000328:Adult; D005260:Female; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000098:blood supply* / Q000000981:diagnostic imaging*; D008297:Male; D011187:Posture / Q000502:physiology*; D011652:Pulmonary Circulation / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D055815:Young Adult