On Earth, gravity exerts a downward force to keep fluids flowing to the lower body. Yet in space, fluids tend to redistribute toward the chest and head. As a consequence, some astronauts may experience brain edema (swelling due to an increase of fluid) and increased intracranial pressure. Neurosurgeons measure intracranial pressure by placing a device into several areas of the cranium. However, such a procedure is not possible on a space mission. Dr. Pierre D. Mourad is developing a simple, noninvasive method of monitoring intracranial pressure while in space.
Prototype Testing for Noninvasive Determination of Intracranial Pressure
Pierre D. Mourad, Ph.D.
University of Washington
Intracranial pressure (ICP) is a vital determinant of brain function. Monitoring and treatment of ICP are central to the successful management of patients with a variety of brain diseases and disorders. There are also indications that changes in cerebral autoregulation – one of the primary physiologial mechanisms for maintaining normal ICP and detectable via alteration of blood flow into the brain – can be altered during spaceflight in ways associated with space motion sickness and orthostatic intolerance. Currently, ICP is measured by drilling a hole into the skull and placing a device into one of several places within the cranium. This is clearly not an option available to astronauts in space, who often develop brain edema and its associated increase in ICP.
Therefore, a simple, noninvasive method of monitoring ICP (nICP) would allow measurement of this critical parameter in astronauts. We have developed several algorithms for nICP based on several different and novel analysis methods, most of which use data derived from standard diagnostic ultrasound of the brain and invasively and continually monitored arterial blood pressure (ABP). We have shown it to be feasible. We have also assembled and tested a device that allows collection of the data necessary to implement in real time and to further refine this algorithm.
1. To test the feasibility of our approach to determining nICP on humans at several hospitals using invasive ABP (iABP), by collecting additional patient data to be used for refining the existing algorithm.
2. To perform the same feasibility tests and algorithm refinement with noninvasive ABP (nABP).
This project will perform the steps necessary to implement a noninvasive means of determining ICP in space.
Noninvasively predicting intracranial pressure (nICP): Patent literature, and to a lesser extent, scientific literature, are littered with failed attempts to determine ICP in a noninvasive fashion. These considerable efforts have been motivated by the vital role played by this medical variable in the management of individuals suffering from head trauma, subarachnoid hemorrhage and other sources of intracranial bleeding, as well as from brain tumors, hydrocephalus and edema, among other disorders. We have demonstrated in our preliminary work, as well as in our on-going efforts, several novel means of predicting nICP. This novel method has the best chance to date to capture this critical medical parameter. Currently, ICP measurement requires that a neurosurgeon drill a hole through the skull.
In work with our industrial collaborators, we have successfully automated the transcranial Doppler process for the purposes of deriving medically useful information from measurements of blood flow rate in the middle cerebral artery. Given such a system, this would allow researchers and clinicians to easily and autonomously measure the rate of blood flow into the brain. This measurement is of intrinsic value and a critical parameter in our approach to the noninvasive determination of ICP. This system would also allow quantification of the existence and extent of emboli transport into the brain and the quality of cerebral autoregulation. The monitoring of these measurements plays an important role in guiding the medical and/or surgical care of patients with a variety of neurologic disorders.