Bone Marrow Pressure Changes under an Inflatable Tourniquet

HAND ◽  
1983 ◽  
Vol os-15 (1) ◽  
pp. 3-8 ◽  
Author(s):  
J. C. Griffiths ◽  
M. Sankarankutty
Keyword(s):  
Blood Pressure ◽  
Bone Marrow ◽  
Early Stage ◽  
Theoretical Calculations ◽  
Elastic Solid ◽  
Shear Stresses ◽  
Fluid Shift ◽  
Intramedullary Pressure ◽  
Tissue Interface ◽  
Pressure Changes

Theoretical calculations suggest that under a limb tourniquet, the pressure at the bone/tissue interface is greater than it is more peripherally. The central bony core must be incompressible for this hypothesis to be correct. Experiments designed to measure the intramedullary pressure confirm that this pressure does not rise at tourniquet pressures above the systolic blood pressure. It has also been suggested that shear stresses are the most likely cause of nerve damage under a tourniquet but this depends on the conversion of the tissue under compression into a fibro-elastic solid. This is likely to occur when all fluid has been driven out. From the experiments such a fluid shift does not seen to occur via the intramedullary cavity but it must nevertheless occur at an early stage of rising tourniquet pressure, probably by fluid shift through the veins proximal and distal to the tourniquet.

Self-Cleansing Flexible Stent for Prevention of Clogging of Blood Vessels

2007 ◽  
Author(s):  
Solomon W. Leung ◽  
Arya Ebrahimpour ◽  
Marco P. Schoen ◽  
James C. K. Lai
Keyword(s):  
Blood Pressure ◽  
Blood Vessel ◽  
Blood Vessels ◽  
Mechanical Design ◽  
Physiological Model ◽  
Shear Stresses ◽  
Optimized Design ◽  
Tissue Fluid ◽  
The One ◽  
Pressure Changes

Different types of stents are available to be implanted into blood-vessels (e.g., cardiovascular stent) or organs to maintain unobstructed blood flow or flow of tissue fluid through ducts (e.g., biliary and uretic stents and others). On the one hand, it is imperative to use smart material such that its mechanical and elastic properties meet those of the ideal stent. A smart stent can change the orientation of the material(s) either by sensing control, temperature, or blood pressure, thus alter the overall shape of the stent (wiggling). These wiggling motions can prevent or reduce the deposit of cholesterol inside the stent’s lumen. On the other hand, there is a need for a better physiological model of how the tensile and shear stresses of a blood vessel are altered as the blood pressure changes along a defined length of that vessel and how the shape changes of the blood vessel could prevent the deposits of lipid material on the vessel wall thereby possibly decrease the likelihood of stenosis. However, the design of an ideal stent is complicated by the lack of proper materials and modeling studies, and difficulties to have an optimized design because of complexities of environmental factors. In this literature review, we therefore propose that an optimal stents design should incorporate the use of highly biocompatible material(s) of well characterized properties and with an adequately modeled mechanical design. We have discussed the importance and relevance of these issues for future stent design and fabrication.

Heart Rate Signal Decomposition

2000 ◽  
Vol 39 (02) ◽  
pp. 200-203
Author(s):  
H. Mizuta ◽  
K. Yana
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Pressure Change ◽  
Normal Subjects ◽  
Signal Decomposition ◽  
Large Individual ◽  
Heart Rate Fluctuations ◽  
Type Pattern ◽  
Signal Cancellation ◽  
Pressure Changes

Abstract:This paper proposes a method for decomposing heart rate fluctuations into background, respiratory and blood pressure oriented fluctuations. A signal cancellation scheme using the adaptive RLS algorithm has been introduced for canceling respiration and blood pressure oriented changes in the heart rate fluctuations. The computer simulation confirmed the validity of the proposed method. Then, heart rate fluctuations, instantaneous lung volume and blood pressure changes are simultaneously recorded from eight normal subjects aged 20-24 years. It was shown that after signal decomposition, the power spectrum of the heart rate showed a consistent monotonic 1/fa type pattern. The proposed method enables a clear interpretation of heart rate spectrum removing uncertain large individual variations due to the respiration and blood pressure change.

scholarly journals Ambulance deceleration causes increased intra cranial pressure in supine position: a prospective observational prove of principle study

2021 ◽  
Vol 29 (1) ◽  
Author(s):  
Iscander M. Maissan ◽  
Boris Vlottes ◽  
Sanne Hoeks ◽  
Jan Bosch ◽  
Robert Jan Stolker ◽  
...  
Keyword(s):  
Supine Position ◽  
Scientific Evidence ◽  
Injured Patient ◽  
Upright Position ◽  
Fluid Shift ◽  
Nerve Sheath ◽  
Head Injured ◽  
Acceleration And Deceleration ◽  
Pressure Changes ◽  
Intra Cranial Pressure

Abstract Background Ambulance drivers in the Netherlands are trained to drive as fluent as possible when transporting a head injured patient to the hospital. Acceleration and deceleration have the potential to create pressure changes in the head that may worsen outcome. Although the idea of fluid shift during braking causing intra cranial pressure (ICP) to rise is widely accepted, it lacks any scientific evidence. In this study we evaluated the effects of driving and deceleration during ambulance transportation on the intra cranial pressure in supine position and 30° upright position. Methods Participants were placed on the ambulance gurney in supine position. During driving and braking the optical nerve sheath diameter (ONSD) was measured with ultrasound. Because cerebro spinal fluid percolates in the optical nerve sheath when ICP rises, the diameter of this sheath will distend if ICP rises during braking of the ambulance. The same measurements were taken with the headrest in 30° upright position. Results Mean ONSD in 20 subjects in supine position increased from 4.80 (IQR 4.80–5.00) mm during normal transportation to 6.00 (IQR 5.75–6.40) mm (p < 0.001) during braking. ONSD’s increased in all subjects in supine position. After raising the headrest of the gurney 30° mean ONSD increased from 4.80 (IQR 4.67–5.02) mm during normal transportation to 4.90 (IQR 4.80–5.02) mm (p = 0.022) during braking. In 15 subjects (75%) there was no change in ONSD at all. Conclusions ONSD and thereby ICP increases during deceleration of a transporting vehicle in participants in supine position. Raising the headrest of the gurney to 30 degrees reduces the effect of breaking on ICP.

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