intrapleural pressure

(noun)

The pressure inside the pleural cavity, which is negative compared to outside air and becomes even more negative during inspiration.

Related Terms

Examples of intrapleural pressure in the following topics:

  • Inspiration

    • The pleural cavity normally has a lower pressure compared to ambient air (-3 mmHg normally and typically -6 mmHg during inspiration), so when it expands, the pressure inside the lungs drops.
    • Pressure and volume are inversely related to eachother, so the drop in pressure inside the lung increases the volume of air inside the lung by drawing outside air into the lung.
    • As the volume of air inside the lung increases, the lung pushes back against the expanded pleural cavity as a result of the drop in intrapleural pressure (pressure inside the pleural cavity).
    • The force of the intrapleural pressure is even enough to hold the lungs open during inpiration despite the natural elastic recoil of the lung.
    • Deeper breaths have higher tidal volumes and require a greater drop in intrapleural compared to shallower breaths.

  • Dead Space: V/Q Mismatch

    • The pulmonary circulation pressure is very low compared to that of the systemic circulation; it is also independent of cardiac output.
    • When someone is standing or sitting upright, the pleural pressure gradient leads to increased ventilation further down in the lung.
    • As a result, the intrapleural pressure is more negative at the base of the lung than at the top; more air fills the bottom of the lung than the top.
    • This is a result of hydrostatic forces combined with the effect of airway pressure.

  • The Work of Breathing

    • In these types of restrictive diseases, the intrapleural pressure is more positive and the airways collapse upon exhalation, which traps air in the lungs.

  • The Mechanics of Human Breathing

    • The relationship between gas pressure and volume helps to explain the mechanics of breathing.
    • As volume decreases, pressure increases and vice versa .
    • This decrease of pressure in the thoracic cavity relative to the environment makes the cavity pressure less than the atmospheric pressure .
    • This increases the pressure within the thoracic cavity relative to the environment.
    • The space between these layers, the intrapleural space, contains a small amount of fluid that protects the tissue by reducing the friction generated from rubbing the tissue layers together as the lungs contract and relax.

  • Gauge Pressure and Atmospheric Pressure

    • 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

  • Measuring Blood Pressure

    • 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 are called segmental blood pressures and 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

  • Introduction to Blood Pressure

    • 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.
    • Therefore, the systolic pressure will show the pressure that your heart emits when blood is forced out of the heart, while diastolic pressure is the pressure exerted when the heart is relaxed.
    • When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation.
    • During each heartbeat, blood pressure varies between a maximum (systolic) and a minimum (diastolic) pressure.

  • Gas Pressure and Respiration

    • 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.

  • Measurements: Gauge Pressure and the Barometer

    • 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.

  • Arterial Blood Pressure

    • 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 which is defined as the pressure exerted by circulating blood upon the walls of blood vessels.
    • Pressure is typically measured with a blood pressure cuff or sphygmomanometer wrapped around a person's upper arm which measured 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 nowadays it is recognized that both high systolic pressure and high pulse pressure (the numerical difference between systolic and diastolic pressures) are also risk factors.