Effects of lower body negative pressure on critical closing pressure and brain tissue mechanics in healthy young adults
| Autor: | Fiona Horvat, Mary Kramer, Curtis Johnson, Christopher Martens |
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| Rok vydání: | 2023 |
| Předmět: | |
| Zdroj: | Physiology. 38 |
| ISSN: | 1548-9221 1548-9213 |
| Popis: | BACKGROUND: Elastography has emerged as a powerful tool for assessing the viscoelastic mechanical properties of the brain which are believed to reflect the microstructural integrity of neuronal tissue. Little is known about the influence of hemodynamic properties, including alterations of intracranial pressure (ICP) on brain tissue properties, which may be important for proper brain functioning. PURPOSE: The purpose of this study was to determine whether acute application of lower body negative pressure (LBNP) alters brain tissue mechanical properties via reductions in ICP. METHODS: 10 participants (8F/2M, age: 23±2 y; BMI: 24±2 kg/m2; BP: 111±6/73±6 mmHg) were included in this study. All participants laid supine with their lower limbs in a negative pressure chamber. Arterial blood pressure (ABP) was measured by finger plethysmography and heart rate was recorded using a 3-lead electrocardiogram (Finapres, NOVA, Medical Systems, Enschede, the Netherlands). Right middle cerebral artery blood velocity (MCAv) was assessed by transcranial Doppler ultrasound. All measures were made at rest and in response to -30mmHg LBNP, which was applied over three repeated 10-minute intervals with 10 minutes of rest in between each interval. Critical closing pressure (CrCP) was calculated as a surrogate measure of ICP using the X-intercept from a best-fit line between ABP and MCAv. The same LBNP protocol was then repeated inside a Siemens 3T Prisma MRI scanner to measure global brain tissue stiffness using magnetic resonance elastography (MRE; 3-min sequence). The last 2-minutes of vascular data for each interval was averaged for all outcomes and the effects of LBNP (off vs. on) and repeated interval (1, 2, 3) were examined using a mixed effects model. RESULTS: Heart rate was significantly elevated during application of LBNP (off: 66±23 vs. on: 76±12 BPM; p-value=0.001) confirming expected vascular effects of LBNP. There was no main effect of LBNP on either stiffness or CrCP; however, stiffness increased with each subsequent application of LBNP, resulting in a main effect of interval on brain stiffness (p-value=0.018). CONCLUSION: These preliminary data suggest brain stiffness increases with repeated application of -30 mmHg LBNP; however, this does not appear to be caused by a change in critical closing pressure and thus ICP. Future studies should further examine alternative mechanisms by which vascular function relates to brain tissue properties. University of Delaware Research Foundation This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process. |
| Databáze: | OpenAIRE |
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