Development of fMRI compatible lower body negative pressure system

The lower body negative pressure (LBNP) system provides a controlled, measured orthostatic stress to the cardiovascular system, which can be used with a magnetic resonance imaging (MRI) machine to study cardiovascular and cerebrovascular responses to graded LBNP. In the past, even though functional MRI (fMRI) was considered as one of the best modalities with which to measure small metabolic changes in the brain, it has not been used with an LBNP system to measure cerebrovascular changes. This was due to the lack of an fMRI compatible LBNP system. In this project, an tMRI compatible LBNP system was first constructed without using any ferromagnetic materials. The LBNP system was then tested to verify its compatibility with an MRI system. Concurrently, a software program was also developed for data acquisition and analysis. Using the developed software, an electrocardiogram (ECG) and measurements of blood pressure, heart rate, chamber pressure and blood flow in the brain were collected at 3 minutes each of 0, -10, -20, -30, -40 and -50 mm Hg lower body suction to confirm the accuracy and the reliability of the developed system. The measured heart rate increased and changes of blood flow in the brain decreased with the graded LBNP. The results of this pilot study support the literature. It has been demonstrated that this newly developed LBNP system is fMRI compatible, accurate, safe to use, reliable and can be used to study cardiovascular and cerebrovascular responses to graded LBNP