Our Research
The general research interests of the Cerebral & Cardiovascular Physiology Laboratory encompass understanding vital organ perfusion in humans under physiological stress. The laboratory is specifically focused on the regulation of brain blood flow and oxygenation during stressors that challenge cerebral perfusion such as traumatic hemorrhage, cardiac arrest, and stroke. A major research focus has been on the early detection of hemorrhagic injury in trauma patients, characterizing physiological differences between individuals with high versus low tolerance to this stress. In addition to investigating these physiological mechanisms, we also collaborate with academic, industry, and government partners to develop and test sensor technologies that may improve the early detection of tissue hypoperfusion in clinical settings. We also study potential therapies that may improve cardiovascular and cerebrovascular tolerance to hypoperfusion, including resistance breathing, pulsatile perfusion therapy, and occlusive exercise.
Core Research Concepts & Techniques
Cerebral Blood Flow
We study how cerebral blood flow responds to a variety of physiological stimuli, including simulated hemorrhage and oscillations in arterial pressure and blood flow.
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We utilize a variety of tools to assess cerebral blood flow in human participants, including transcranial Doppler ultrasound (intracranial velocity), duplex Doppler ultrasound (extracranial blood flow), and advanced imaging approaches such as MRI (e.g., phase contrast).
Tissue Oxygenation
In addition to blood flow and oxygen delivery to the tissues, we are very interested in examining end organ tissue oxygenation responses to simulated hemorrhage and oscillations in arterial pressure and blood flow.
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We use near-infrared spectroscopy (NIRS) to assess both cerebral and peripheral oxygenation, and we have recently started studies using BOLD-MRI for global and regional assessment of cerebral tissue oxygenation.
Lower Body Negative Pressure
Lower Body Negative Pressure (LBNP) is a technique we employ to safely simulate blood loss in human participants. Application of a vacuum within the LBNP chamber redistributes blood volume to the lower limbs, leading to decreases in venous return, stroke volume, cardiac output, arterial pressure, and cerebral blood flow and tissue oxygenation.
Pulsatile Perfusion Therapy (PPT)
Individuals with higher tolerance to simulated hemorrhage via application of LBNP, exhibit cyclical waves (or oscillations) in arterial pressure and blood flow (see left panels). These naturally-occurring oscillations occur about every 10 seconds (or 0.1 Hz). Our research is now focused on exploring methods to induce these 0.1 Hz hemodynamic oscillations, which we call "Pulsatile Perfusion Therapy (PPT)", and understanding how PPT can increase tolerance to hemorrhage, and protect vital organ perfusion and tissue oxygenation under conditions of tissue hypoperfusion.