El arte de medicina consiste en entretener al paciente mientras la naturaleza cura la enfermedad. Voltaire Los doctores son hombres que prescriben medicinas que conocen poco, curan enfermedades que conocen menos, en seres humanos de los que no saben nada. Los doctores son hombres que prescriben medicinas que conocen poco, curan enfermedades que conocen menos, en seres humanosde los que no sabennada.
|Published (Last):||4 September 2016|
|PDF File Size:||8.9 Mb|
|ePub File Size:||13.37 Mb|
|Price:||Free* [*Free Regsitration Required]|
El arte de medicina consiste en entretener al paciente mientras la naturaleza cura la enfermedad. Voltaire Los doctores son hombres que prescriben medicinas que conocen poco, curan enfermedades que conocen menos, en seres humanos de los que no saben nada. Los doctores son hombres que prescriben medicinas que conocen poco, curan enfermedades que conocen menos, en seres humanosde los que no sabennada. Transpulmonary pressure is the difference between the alveolar pressure mmHg and the interpleural pressure mmHg.
At rest the forces tending to collapse the lung, surface tension and tissue elastic recoil, are pulling the lungs away from the chest wall. Since the interplural space is filled with fluid, it only slightly expands. This small increase in size reduces the interplural pressure below atmospheric. Thus at rest the lungs are being held against the chest wall by a small vacuum.
Observe como se mueven las flechas que representan las presiones alveolar y pleural. No existe flujo de aire. The inflow during inspiration is shown in negative value, and the outflow during expiration is shown in positive value. The red line shows the lungs and the outer grey line shows the chest wall. The cavity inside the chest wall is the thoracic cavity. The diaphragm is at the bottom of the thoracic cavity. Red indicates that the diaphragm is contracting. When the diaphragm contracts, the thoracic cavity increases in volume and inflates the lungs.
This process is the inspiration. The volume of gas inside the lungs is called 'lung volume'. With diaphragm contraction, the lung volume increases. Blue indicates that the diaphragm is relaxed. With diaphragm relaxation, the lung volume decreases. This process is the expiration. The decrease in volume is due to the elasticity of the lungs, which will be discussed later. Due to the negative pressure, gas airs flows into the lungs. When the lungs remain increased at a constant volume, the negative pressure disappears and the flow ceases.
The yellow pressure gauge indicates the pressure inside the lungs. The pressure inside the lungs are also called alveolar pressure, to specify anatomic location. When the lungs are increasing in volume, the pressure inside the lungs alveolar pressure are negative compared to the atmospheric pressure. Note that the yellow pressure gauge is elevated on the lung side, compared to the outer-side, which is open and thus indicates the atmospheric pressure.
Due to the positive pressure, the gas inside the lungs flows out. When the lungs remain decreased at a constant volume, the positive pressure disappears and the flow ceases. When the lungs are decreasing in volume, the pressure inside the lungs alveolar pressure are positive compared to the atmospheric pressure.
Note that the yellow pressure gauge is lowered on the lung side, compared to the outer-side, which is open and thus indicates the atmospheric pressure. This works towards decreasing the lung volume. The larger the lung volume, the larger the elastic force. Let's suppose that there are 'rubber bands' inside the lungs, and that they are lightly stretched.
When the lung volume is increased, the 'rubber bands' are strongly stretched. Because of inward elastic force of the lungs and the outward elastic forces of the chest wall, the pressure between the lungs and the chest wall is negative. The pleural pressure, which is the pressure between the lungs and the chest wall, is negative note that the blue pressure gauge on the lung side is elevated.
With inspiration, the lung volume increases and the inward elastic force of the lungs increases. To counteract this force and increase the lung volume, the chest wall exerts a larger outward force. This makes the negative pleural pressure larger. The inward elasticity of the lungs and the outward elasticity of the chest wall are balanced. The pleural pressure is negative. The pressure inside the lungs alveolar pressure is equal to the atmospheric pressure and there is no gas air flow.
Since the lung volume within a quiet breath is at its minimum, the lung elastic force and the pleural pressure are also at their minimum. There still are no changes in pressure, lung volume, etc. Because of the water, the lung volume is also increased. Since this is in the opposite direction of the lung elasticity note that the 'rubber bands' are further stretched , the negative pleural pressure becomes larger note the blue pressure gauge.
With lung volume increasing,the pressure inside the lungs alveolar pressure becomenegative, compared to theatmospheric pressure, causinggas air inflow into the lungs. At the end of inspiration The lung elasticity reaches its maximum note that the 'rubber bands' are strongly stretched , thus, the negative pleural pressure reaches its maximum within a quiet breath. The lung volume cease increasing. Without lung movement, pressure inside the lungs alveolar pressure is equal to the atmospheric pressure and the air inflow inspiration ceases.
Thus, due to the elasticity of the lungs, the lungs and thoracic cavity decrease in volume. Naturally, the negative pleural pressure is smaller than at the end of inspiration beginning of expiration. Because the lungs decrease in volume, the pressure inside the lungs alveolar pressure become positive compared to the atmospheric pressure.
The positive pressure pushes out the gas inside the lungs because of O2 and CO2 exchange with the blood, it is no longer 'air' outward through the trachea expiration. When the inward elasticity of the lungs balances with the outward elasticity of the chest wall, expiration ends. Naturally, the negative pleural pressure and lung volume is at their minimum within a quiet breath. When the lung volume cease to decrease, pressure inside the lungs alveolar pressure become equal to the atmospheric pressure and the gas outflow expiration ceases.
This is the same illustration as in "quiet breath: When the respiratory muscles are relaxed and there are no respiratory movement". Repeatedly, the diaphragm contracts and the cycle is repeated. Changes in lung volume, air flow, intrapleural pressure, and alveolar pressure during normal tidal breathing. The dashed intrapleural pressure line would be followed if there were no airway resistance.
The diagram at the left shows the lung and a spirometer measuring the changes. This figure depicts changes in the main parameters of interest during a normal ventilatory cycle in which a Tidal Volume of - ml is being inspired and expired with each breath quiet breathing. Inspiration is indicated by a downward deflection in the first panel. Note that during the entire ventilatory cycle, the intrapleural pressure Ppl remains negative 2nd panel.
The plot normally follows the solid blue line; alternatively it follows the dashed line when where there is no resistance to air flow imaginary situation. Note that alveolar pressure bottom panel has a non-zero value only when there is air flowing. Effect on distribution of ventilation due to inspiration from FRC panel A vs.
Because of the way in which the lungs are suspended in the chest cavity and are subjected to gravity, a gradient in pleural pressure exists from the apex top, blue to the base, of about 7. Thus apical alveoli will be less able to accommodate further increase in volume i.
Thus, if inspiration starts from FRC, most of the incoming air goes preferentially to basally located alveoli which began less distended and thus more compliant. If inspiration starts from RV following a very energetic expiration to get below FRC , all the incoming air goes initially to apical alveoli where pleural pressure is still negative -4 cm H2O.
Thus air inflow is initially prevented in that area until basal pressures become negative again and allow airway opening. Create Presentation Survey Quiz Lead-form. Download Presentation. Skip this Video. Loading SlideShow in 5 Seconds.. Share Presentations.
Email Presentation to Friend. Related More by user.
Palabras clave: Anestesia. Consorcio Hospital General Universitario de Valencia. Carlos L. Universidad de Valencia. Citas 1.