Group 1: Mueller maneuver
inferior vena cava, PIU
CAVITY, CONTRACTION
The Mueller maneuver was performed using a dedicated prototype Contrast Booster system (Contrast Booster™ System, Ulrich GmbH & Co. KG) which allows both the patient via bio-feedback and the radiological staff outside the scanner room to monitor the correct performance of the Mueller maneuver throughout the scan and interact with the patient at any time. The system consists of a patient interface unit (PIU) and two charger and communication units which are wirelessly connected via Bluetooth. The PIU consists of a battery, a pressure sensor, and a visual display. A green light centrally on the bio-feedback light-emitting diode (LED) band indicates that he or she is sucking at the correct intensity level. An orange or red light, on the other hand, indicates suction to be either too strong or too weak. The investigator in the control room sees the same visual feedback on the visual display of the Charger and communication unit (CCU) and instructs via microphone, the patient to start sucking shortly after i.v. contrast injection starts to generate a continuous negative pressure. At this moment there is a massive contraction of the diaphragm on the inferior vena cava, resulting in interruption of the venous uncontrasted blood flow from the abdominal cavity in the direction of the right atrium. At the same time, there is a significant increase in the flow of the superior vena cava, with which the bolus of contrast medium reaches the right atrium and thus the pulmonary artery in a highly concentrated form, without being diluted by the non-contrasted blood from the blood of the abdominal cavity [To control breathing command during suction against resistance, the flow volume curve is displayed to the investigator on a tablet PC, Samsung Tab A (Samsung Electronics Co., Ltd.) with an Android operating system Version 5.1.1 (Open Handset Alliance).