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Peripheral Arterial Tone
Peripheral Arterial Tone (PAT) is a noninvasive measure designed to track pulsatile volume changes in peripheral arterial beds. The collected information gives specialists important insight into the autonomic nervous system and the cardiovascular system. PAT technology is mostly used to detect heart disease, erectile dysfunction and obstructive sleep apnea. The PAT technology The PAT signal is a form of pulse wave amplitude measured by incorporating both a unified pressure field and a specific isosbestic wavelength. Applying a uniform pressure field around the measured surface releases arterial wall motion restriction, magnifies the dynamic range of the recorded signal, and prevents the distention of the veins distal to the site of pressure application. The use of an isosbestic wavelength results in both oxyhaemoglobin and deoxyhaemoglobin having the same absorption level, thereby preventing oxygen saturation level changes. These features result in high signal quality which differe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulsatile
In fluid dynamics, a flow with periodic variations is known as pulsatile flow, or as Womersley flow. The flow profiles was first derived by John R. Womersley (1907–1958) in his work with blood flow in arteries. The cardiovascular system of chordate animals is a very good example where pulsatile flow is found, but pulsatile flow is also observed in engines and hydraulic systems, as a result of rotating mechanisms pumping the fluid. Equation The pulsatile flow profile is given in a straight pipe by : u(r, t) = \mathrm\left\ \, , where: : Properties Womersley number The pulsatile flow profile changes its shape depending on the Womersley number :\alpha = R \left( \frac \right)^ \,. For \alpha \lesssim 2, viscous forces dominate the flow, and the pulse is considered quasi-static with a parabolic profile. For \alpha \gtrsim 2, the inertial forces are dominant in the central core, whereas viscous forces dominate near the boundary layer. Thus, the velocity profile gets ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schematic View Of PAT Probes' Types
A schematic, or schematic diagram, is a designed representation of the elements of a system using abstract, graphic symbols rather than realistic pictures. A schematic usually omits all details that are not relevant to the key information the schematic is intended to convey, and may include oversimplified elements in order to make this essential meaning easier to grasp, as well as additional organization of the information. For example, a subway map intended for passengers may represent a subway station with a dot. The dot is not intended to resemble the actual station at all but aims to give the viewer information without unnecessary visual clutter. A schematic diagram of a chemical process uses symbols in place of detailed representations of the vessels, piping, valves, pumps, and other equipment that compose the system, thus emphasizing the functions of the individual elements and the interconnections among them and suppresses their physical details. In an electronic circuit d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sleep Disordered Breathing
When we sleep, our breathing changes due to normal biological processes that affect both our respiratory and muscular systems. Physiology Sleep Onset Breathing changes as we transition from wakefulness to sleep. These changes arise due to biological changes in the processes that regulate our breathing. When we fall asleep, minute ventilation (the amount of air that we breathe per minute) reduces due to decreased metabolism. Non-REM (NREM) Sleep During NREM sleep, we move through three Sleep, sleep stages, with each progressively deeper than the last. As our sleep deepens, our minute ventilation continues to decrease, reducing by 13% in the second NREM stage and by 15% in the third. For example, a study of 19 healthy adults revealed that the Respiratory minute volume, minute ventilation in NREM sleep was 7.18 liters/minute compared to 7.66 liters/minute when awake. Ribcage & Abdominal Muscle Contributions Human rib cage, Rib cage contribution to ventilation increases during NREM s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Young–Laplace Equation
In physics, the Young–Laplace equation () is an equation that describes the capillary pressure difference sustained across the interface between two static fluids, such as water and air, due to the phenomenon of surface tension or wall tension, although use of the latter is only applicable if assuming that the wall is very thin. The Young–Laplace equation relates the pressure difference to the shape of the surface or wall and it is fundamentally important in the study of static capillary surfaces. It is a statement of normal stress balance for static fluids meeting at an interface, where the interface is treated as a surface (zero thickness): \begin \Delta p &= -\gamma \nabla \cdot \hat n \\ &= -2\gamma H_f \\ &= -\gamma \left(\frac + \frac\right) \end where \Delta p is the Laplace pressure, the pressure difference across the fluid interface (the exterior pressure minus the interior pressure), \gamma is the surface tension (or wall tension), \hat n is the unit normal poi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Density
Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". Alternatively, for samples which scatter light, absorbance may be defined as "the negative logarithm of one minus absorptance, as measured on a uniform sample". The term is used in many technical areas to quantify the results of an experimental measurement. While the term has its origin in quantifying the absorption of light, it is often entangled with quantification of light which is "lost" to a detector system through other mechanisms. What these uses of the term tend to have in common is that they refer to a logarithm of the ratio of a quantity of light incident on a sample or material to that which is detected after the light has interacted with the sample. The term absorption refers to the physical process of absorbing light, while absorbance does not always measure only absorption; it may measure attenuation (of transmitted ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pneumatic
Pneumatics (from Greek 'wind, breath') is the use of gas or pressurized air in mechanical systems. Pneumatic systems used in Industrial sector, industry are commonly powered by compressed air or compressed inert gases. A centrally located and electrically-powered Gas compressor, compressor powers Pneumatic cylinder, cylinders, air motors, pneumatic actuators, and other pneumatic devices. A pneumatic system controlled through manual or automatic solenoid valves is selected when it provides a lower cost, more flexible, or safer alternative to electric motors, and hydraulic actuators. Pneumatics also has applications in dentistry, construction, mining, and other areas. History Although the early history of pneumatics is somewhat unclear, blowguns are often considered the earliest pneumatic device, being created independently by various indigenous groups around the world. Bellows are an early form of air compressor used primarily for smelting and forging. Ctesibius of Alexand ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endothelial
The endothelium (: endothelia) is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall. Endothelial cells in direct contact with blood are called vascular endothelial cells whereas those in direct contact with lymph are known as lymphatic endothelial cells. Vascular endothelial cells line the entire circulatory system, from the heart to the smallest capillaries. These cells have unique functions that include fluid filtration, such as in the glomerulus of the kidney, blood vessel tone, hemostasis, neutrophil recruitment, and hormone trafficking. Endothelium of the interior surfaces of the heart chambers is called endocardium. An impaired function can lead to serious health issues throughout the body. Structure The endothelium is a thin layer of single flat (squamous) cells that line the interior su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sleep Apnea
Sleep apnea (sleep apnoea or sleep apnœa in British English) is a sleep-related breathing disorder in which repetitive Apnea, pauses in breathing, periods of shallow breathing, or collapse of the upper airway during sleep results in poor ventilation and sleep disruption. Each pause in breathing can last for a few seconds to a few minutes and often occurs many times a night. A choking or snorting sound may occur as breathing resumes. Common symptoms include daytime sleepiness, snoring, and non restorative sleep despite adequate sleep time. Because the disorder disrupts normal sleep, those affected may experience sleepiness or feel tired during the day. It is often a chronic condition. Sleep apnea may be categorized as obstructive sleep apnea (OSA), in which breathing is interrupted by a blockage of air flow, central sleep apnea (CSA), in which regular unconscious breath simply stops, or a combination of the two. OSA is the most common form. OSA has four key contributors; these ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mental Stress
In psychology, stress is a feeling of emotional strain and pressure. Stress is a form of psychological pain, psychological and mental discomfort. Small amounts of stress may be beneficial, as it can improve athletic performance, motivation and reaction to the environment. Excessive amounts of stress, however, can increase the risk of strokes, myocardial infarction, heart attacks, ulcers, and diathesis stress model, mental illnesses such as Depression (mood), depression and also aggravate pre-existing conditions. Psychological stress can be external and related to the environment, but may also be caused by internal perceptions that cause an individual to experience anxiety or other negative emotions surrounding a situation, such as pressure, discomfort, etc., which they then deem stressful. Hans Selye (1974) proposed four variations of stress. On one axis he locates good stress (eustress) and bad stress (distress). On the other is over-stress (hyperstress) and understress (hypo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adrenergic Receptors
The adrenergic receptors or adrenoceptors are a class of G protein-coupled receptors that are targets of many catecholamines like norepinephrine (noradrenaline) and epinephrine (adrenaline) produced by the body, but also many medications like beta blockers, beta-2 (β2) agonists and alpha-2 (α2) agonists, which are used to treat high blood pressure and asthma, for example. Many cells have these receptors, and the binding of a catecholamine to the receptor will generally stimulate the sympathetic nervous system (SNS). The SNS is responsible for the fight-or-flight response, which is triggered by experiences such as exercise or fear-causing situations. This response dilates pupils, increases heart rate, mobilizes energy, and diverts blood flow from non-essential organs to skeletal muscle. These effects together tend to increase physical performance momentarily. History By the turn of the 19th century, it was agreed that the stimulation of sympathetic nerves could cause di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sympathetic Nervous System
The sympathetic nervous system (SNS or SANS, sympathetic autonomic nervous system, to differentiate it from the somatic nervous system) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system. The autonomic nervous system functions to regulate the body's unconscious actions. The sympathetic nervous system's primary process is to stimulate the body's fight or flight response. It is, however, constantly active at a basic level to maintain homeostasis. The sympathetic nervous system is described as being antagonistic to the parasympathetic nervous system. The latter stimulates the body to "feed and breed" and to (then) "rest-and-digest". The SNS has a major role in various physiological processes such as blood glucose levels, body temperature, cardiac output, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ischemic
Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems with blood vessels, with resultant damage to or dysfunction of tissue, i.e., hypoxia and microvascular dysfunction. It also implies local hypoxia in a part of a body resulting from constriction (such as vasoconstriction, thrombosis, or embolism). Ischemia causes not only insufficiency of oxygen but also reduced availability of nutrients and inadequate removal of metabolic wastes. Ischemia can be partial (poor perfusion) or total blockage. The inadequate delivery of oxygenated blood to the organs must be resolved either by treating the cause of the inadequate delivery or reducing the oxygen demand of the system that needs it. For example, patients with myocardial ischemia have a decreased blood flow to the heart and are prescribed w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
