Examples of pressure in the following topics:
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- Pressure is often measured as gauge pressure, which is defined as the absolute pressure minus the atmospheric pressure.
- Gauge pressure is a relative pressure measurement which measures pressure relative to atmospheric pressure and is defined as the absolute pressure minus the atmospheric pressure.
- Most pressure measuring equipment give the pressure of a system in terms of gauge pressure as opposed to absolute pressure.
- For example, tire pressure and blood pressure are gauge pressures by convention, while atmospheric pressures, deep vacuum pressures, and altimeter pressures must be absolute.
- Explain the relationship among absolute pressure, gauge pressure, and atmospheric pressure
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- Measurement of blood pressure includes systolic pressure during cardiac contraction and diastolic pressure during cardiac relaxation.
- Blood pressure is the pressure blood exerts on the arterial walls.
- These pressures, called segmental blood pressures, are used to evaluate blockage or arterial occlusion in a limb (for example, the ankle brachial pressure index).The difference between the systolic and diastolic pressure is called the pulse pressure.
- A blood pressure cuff and associated monitor used for determining systolic and diastolic pressures within an artery.
- Explain how blood pressure is measured and the ranges of blood pressure readings
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- Blood pressure is a vital sign reflecting the pressure exerted on blood vessels when blood is forced out of the heart during contraction.
- Blood pressure is the pressure that blood exerts on the wall of the blood vessels.
- Systolic pressure is thus the pressure that your heart emits when blood is forced out of the heart and diastolic pressure is the pressure exerted when the heart is relaxed.
- During each heartbeat, blood pressure varies between a maximum (systolic) and a minimum (diastolic) pressure.
- A normal blood pressure should be around 120/80, with the systolic pressure expressed first.
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- Gas pressures in the atmosphere and body determine gas exchange: both O2 and CO2 will flow from areas of high to low pressure.
- Each gas component of that mixture exerts a pressure.
- The pressure for an individual gas in the mixture is the partial pressure of that gas.
- The pressure of the water vapor in the lung does not change the pressure of the air, but it must be included in the partial pressure equation.
- For this calculation, the water pressure (47 mm Hg) is subtracted from the atmospheric pressure: 760 mm Hg 47 mm Hg = 713 mm Hg, and the partial pressure of oxygen is: (760 mm Hg 47 mm Hg) 0.21 = 150 mm Hg.
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- In practice, pressure is most often measured in terms of gauge pressure.
- Gauge pressure is the pressure of a system above atmospheric pressure.
- Gauge pressure is much more convenient than absolute pressure for practical measurements and is widely used as an established measure of pressure.
- Barometers are devices used to measure pressure and were initially used to measure atmospheric pressure.
- Many modern pressure measuring devices are pre-engineered to output gauge pressure measurements.
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- Blood pressure is the pressure of blood against the blood vessel walls during the cardiac cycle; it is influenced by a variety of factors.
- Blood pressure is the pressure of the fluid (blood) against the walls of the blood vessels.
- Fluid will move from areas of high to low hydrostatic pressures.
- The systolic pressure is defined as the peak pressure in the arteries during the cardiac cycle; the diastolic pressure is the lowest pressure at the resting phase of the cardiac cycle.
- The blood pressure of the systole phase and the diastole phase gives the two readings for blood pressure .
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- Gibbs free energy measures the useful work obtainable from a thermodynamic system at a constant temperature and pressure.
- When a system changes from an initial state to a final state, the Gibbs free energy (ΔG) equals the work exchanged by the system with its surroundings, minus the work of the pressure force.
- Gibbs energy (also referred to as ∆G) is also the chemical potential that is minimized when a system reaches equilibrium at constant pressure and temperature.
- As such, it is a convenient criterion of spontaneity for processes with constant pressure and temperature.
- Therefore, Gibbs free energy is most useful for thermochemical processes at constant temperature and pressure.
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- Pressure is defined in simplest terms as force per unit area.
- However, when dealing with pressures exerted by gases and liquids, it is most convenient to approach pressure as a measure of energy per unit volume by means of the definition of work (W = F·d).
- For liquids and gases at rest, the pressure of the liquid or gas at any point within the medium is called the hydrostatic pressure.
- As a result, pressure within a liquid is therefore a function of depth only, with the pressure increasing at a linear rate with respect to increasing depth.
- Equation 2 by itself gives the pressure exerted by a liquid relative to atmospheric pressure, yet if the absolute pressure is desired, the atmospheric pressure must then be added to the pressure exerted by the liquid alone.
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- The measurement of blood pressure without further specification usually refers to systemic arterial pressure measured at the upper arm.
- The measurement of blood pressure without further specification usually refers to the systemic arterial pressure, defined as the pressure exerted by circulating blood upon the walls of blood vessels.
- Pressure is typically measured with a blood pressure cuff (sphygmomanometer) wrapped around a person's upper arm, which measures the pressure in the brachial artery.
- A person's blood pressure is usually expressed in terms of the systolic pressure over diastolic pressure and is measured in millimeters of mercury (mmHg), for example 140/90.
- In the past, most attention was paid to diastolic pressure, but now we know that both high systolic pressure and high pulse pressure (the numerical difference between systolic and diastolic pressures) are also risk factors for disease.
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- Chronically elevated blood pressure is called hypertension, while chronically low blood pressure is called hypotension.
- Hypertension or high blood pressure, sometimes called arterial hypertension, is a chronic medical condition in which the blood pressure in the arteries is elevated above 140/90 mmHg.
- Even moderate elevation of arterial blood pressure is associated with a shortened life expectancy.
- However, blood pressure is considered too low only if noticeable symptoms are present.
- Graph showing changes in blood pressure during a single contraction-relaxation cycle of the heart.