Abstract
Objectives Optimal contrast within the pulmonary artery is
achieved by the maximum amount of contrast-enhanced
blood flowing through the superior vena cava (SVC),
while minimum amounts of non-contrasted blood should
originate from the inferior vena cava (IVC). This study
aims to clarify whether “suction against resistance”
might optimise this ratio.
Methods Phase-contrast pulse sequences on a 1.5T MRI magnet
were used for flow quantification (mean flow (mL/s),
stroke volume (Vol) in the SVC and IVC in volunteers.
Different breathing manoeuvers were analysed repeatedly:
free breathing; inspiration; expiration; suction against resistance,
and Valsalva. To standardise breathing commands,
volunteers performed suction and Valsalva manoeuvers with
an MR-compatible manometer.
Results Suction against resistance was associated with a significant
drop of the IVC/SVC flow quotient (1.63 [range 1.3-
2.0] p