EXPERIMENTAL STUDY OF CLINICAL INDICATORS OF INTRATISSUE PRESSURE IN DEEP CIRCULAR BURNS AND ITS DYNAMICS DEPENDING ON THE NATURE AND VOLUME OF SURGERY

The purpose of research. To improve in the experiment the optimal variants of surgical tactics to eliminate the phenomena of compartment syndrome in circular deep burns on the basis of studying the dynamics of intratissue pressure. Materials and methods. An experiment to study the effectiveness of treatment of deep circular burns of III degree, accompanied by compartment-syndrome with objectification of intra-tissue pressure was performed on 18 male WAG rats weighing 190.0-200.0 g, which were divided into three groups depending from the nature and scope of surgery. Research results and their discussion. Based on the assessment of the dependence of the level of intratissue pressure in the tissues on the timing of modeling of deep circular burns in the experiment and tactics and volume of surgical treatment, a clear dependence of indicators in all groups of experimental animals. The primary necrectomy performed in the III main group due to the radical surgical intervention allowed to completely normalize the intratissue pressure within 24 hours. Conclusions. 1. Clinical indicators of intratissue pressure at deep circular burns depending on time of modeling of a thermal trauma and character and volume of surgical intervention are defined in experiment. 2. It is established that primary necrectomy due to radical excision of necrotized tissues and rapid decompression contributes to the nor malization of intratissue pressure.

Edema, Fainting, and Strokes

High blood pressure in humans is often associated with heart failure, edema, strokes, and episodes of fainting. Giraffes never show these. Edema, the abnormal collection of fluid in the lower legs, is prevented in giraffes by a combination of thick basement membranes of capillary blood vessels, which probably reduce their permeability to proteins, a very high tissue pressure that resists flow of fluid out of capillaries, and efficient mechanisms for returning blood to the heart. Fainting occurs when blood flow (and thus oxygen and glucose supply) to the brain is reduced. When a giraffe lifts its head after drinking water there is a sudden reduction of blood flow to the head, and fainting should result. Fainting is avoided because the blood flow that remains is diverted completely to the brain by a unique arrangement of blood vessels and nerves, and by structures that maintain the perfusion pressure of the blood flowing through the brain. Strokes can be caused by rupture of small blood vessels in the brain when they are exposed to high blood pressure of the kind reached in the head of a giraffe when it drinks surface water. Rupture of brain blood vessels is prevented in giraffes by mechanisms that reduce pressure. The posture adopted while drinking, baroreceptor-mediated reduction in cardiac output, the effects of the carotid rete, diversion of blood away from the brain, an increase in cerebrospinal fluid pressure, and passive and active constriction of blood vessels, all contribute.

Friction Analysis in Needle Insertion Into Soft Tissue

As one of the preoperative diagnostic methods, needle insertion is widely used for its safety and effectiveness. Recently, robotic needle insertion systems have been under active developments. Hence needle insertion experiments are essential for system verifications, in which the interactions between needle and tissue is a major focus for needle-tissue interactive models, and the friction between the needle and tissue is an important factor. In these experiments, the friction coefficient can be affected by many factors, such as insertion speed, needle-tissue deformation and contact forces. In this paper, to study and analyze the influence of various variables on friction force and friction coefficient, three variables, i.e., tissue pressure on needle, needle insertion velocity and Young’s modulus of the tissue, are systematically studied by constructing a testbed, in which the radial surface friction is converted into equivalent plane friction based on the assumption that the distribution of the normal force and friction force on the needle is uniform for the whole needle outer surface. The experimental results show that the variation range of friction coefficient is 0.122–0.341. The friction coefficient decreases with the increase of pressure and increases with the increase of velocity, while Young’s modulus have a small effect on the friction coefficient.

Mechanism of Origin of Positive Tissue Pressure During Negative-Pressure Wound Therapy

This report provides a simplified insight into the previously unexplained physical mechanism of the origin of local positive tissue pressure during negative-pressure wound therapy (NPWT). A chain of 2 spring model could be used to show the biomechanical interaction between the NPWT dressing and the adjacent body tissues. It is important to assume that the application of NPWT dressing to the body surface creates a new closed compartmentalized volume. Air suction generates local positive pressure within the dressing due to unopposed atmospheric load, which in turn leads to compression of the adjacent tissues and induction of positive pressure there. Analysis of the biomechanical events during NPWT implies the possibility of tissue injury by positive pressure and suggests clinical alertness in regard to the balance between the size of the NPWT dressing and suction pressure as well as further related research.

Relation Between Post-Augmentation Parenchymal Atrophy and Local Tissue Pressure

Background Breast parenchyma interacts dynamically with an inserted implant, which may lead to local atrophy and sensory involvement, changes in vascular tissue and lactation, besides volume reduction over time. The inversely proportional relationship between pressure and volume cannot be stated with certainty, that is, the larger implants having more local pressure would lead to compression, thus leading to atrophy of parenchyma more intensely when compared with smaller implants. The objective of this study was to assess and list breast parenchyma volume changes with different pressure levels due to silicone implants of several sizes. Objectives To list the pressure exerted by silicone implants and the atrophy caused in the breast tissue. Methods Thirty-six women were placed in 3 groups (n=12) and subjected to augmentation mammoplasty in the subglandular plane. The measurement of pressure in millimeters of mercury was done with help of molds with the same base and projection of implants introduced posteriorly. The magnetic resonance imaging was done in all participants in the pre-operative period and at 6 and 12 months after surgery. Results Twelve months after breast implant insertion, the groups had a significant glandular volume reduction (mean 12.97% in the right breast and 12.42% in the left breast). There is a statistically significant difference in the proportions of volume reduction and the pressure levels measured. Conclusions A reduction in breast volume was verified. This reduction is also related to the level of pressure exerted on the implant.