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Dynamic Airway Compression
: Dynamic compression of the airways results when intrapleural pressure equals or exceeds alveolar pressure, which causes dynamic collapsing of the lung airways. It is termed ''dynamic'' given the transpulmonary pressure (alveolar pressure − intrapleural pressure) varies based on factors including lung volume, compliance, resistance, existing pathologies, etc. It occurs during forced expiration when intrapleural pressure is greater than atmospheric pressure (positive barometric A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ... values), and not during passive expiration when intrapleural pressure remains at subatmospheric pressures (negative barometric values). Clinically, dynamic compression is most commonly associated to the wheezing sound during forced expiration such as in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intrapleural Pressure
In physiology, intrapleural pressure refers to the pressure within the pleural cavity. Normally, the pressure within the pleural cavity is slightly less than the atmospheric pressure, which is known as ''negative pressure''.Khanorkar, p. 205 When the pleural cavity is damaged or ruptured and the intrapleural pressure becomes greater than the atmospheric pressure, pneumothorax may ensue. Intrapleural pressure is different from intrathoracic pressure. The thoracic cavity is the space that includes the pleura, lungs, and heart, while the pleural space is only the space between the parietal pleura and visceral pleura surrounding lungs. Intrapleural pressure depends on the ventilation phase, atmospheric pressure, and the volume of the intrapleural cavity.Blom, p. 7 At rest, there is a negative intrapleural pressure. This provides a transpulmonary pressure, causing the lungs to expand. If humans didn't maintain a slightly negative pressure even when exhaling, their lungs would collapse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alveolar Pressure
Alveolar pressure (Palv) is the pressure of air inside the lung Pulmonary alveolus, alveoli. When the glottis is opened and no air is flowing into or out of the lungs, alveolar pressure is equal to the atmospheric pressure, that is, zero cmH2O, cmH2O.Guyton and Hall Textbook of Medical Physiology, 12th edition. 23 May 2016 Significance During inhalation, the increased volume of Pulmonary alveolus, alveoli as a result of lung expansion decreases the intra-alveolar pressure to a value below atmospheric pressure about -1 cmH2O. This slight negative pressure is enough to move 500 ml of air into the lungs in the 2 seconds required for inspiration. At the end of inspiration, the alveolar pressure returns to atmospheric pressure (zero cmH2O). During exhalation, the opposite change occurs. The lung alveoli collapse before air is expelled from them. The alveolar pressure rises to about +1 cmH2O. This forces the 500 ml of inspired air out of the lung during the 2–3 seconds of expiratio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lung
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart. Their function in the respiratory system is to extract oxygen from the air and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange. Respiration is driven by different muscular systems in different species. Mammals, reptiles and birds use their different muscles to support and foster breathing. In earlier tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians. In humans, the main muscle of respiration that drives breathing is the diaphragm. The lungs also provide airflow that makes vocal sounds including human speech possible. Humans have two lungs, one on the left and on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transpulmonary Pressure
Transpulmonary pressure is the difference between the alveolar pressure and the intrapleural pressure in the pleural cavity. During human ventilation, air flows because of pressure gradients. Ptp = Palv – Pip. Where Ptp is transpulmonary pressure, Palv is alveolar pressure, and Pip is intrapleural pressure. Physiology Since atmospheric pressure is relatively constant, pressure in the lungs must be higher or lower than atmospheric pressure for air to flow between the atmosphere and the alveoli. If 'transpulmonary pressure' = 0 (alveolar pressure = intrapleural pressure), such as when the lungs are removed from the chest cavity or air enters the intrapleural space (a pneumothorax), the lungs collapse as a result of their inherent elastic recoil. Under physiological conditions the transpulmonary pressure is always positive; intrapleural pressure is always negative and relatively large, while alveolar pressure moves from slightly negative to slightly positive as a person breathes. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lung Volume
Lung volumes and lung capacities refer to the volume of air in the lungs at different phases of the respiratory cycle. The average total lung capacity of an adult human male is about 6 litres of air. Tidal breathing is normal, resting breathing; the tidal volume is the volume of air that is inhaled or exhaled in only a single such breath. The average human respiratory rate is 30–60 breaths per minute at birth, decreasing to 12–20 breaths per minute in adults. Factors affecting volumes Several factors affect lung volumes; some can be controlled, and some cannot be controlled. Lung volumes vary with different people as follows: A person who is born and lives at sea level will develop a slightly smaller lung capacity than a person who spends their life at a high altitude. This is because the partial pressure of oxygen is lower at higher altitude which, as a result means that oxygen less readily diffuses into the bloodstream. In response to higher altitude, the body's diffu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulmonary Compliance
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart. Their function in the respiratory system is to extract oxygen from the air and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange. Respiration is driven by different muscular systems in different species. Mammals, reptiles and birds use their different muscles to support and foster breathing. In earlier tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians. In humans, the main muscle of respiration that drives breathing is the diaphragm. The lungs also provide airflow that makes vocal sounds including human speech possible. Humans have two lungs, one on the left and one ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Airway Resistance
In respiratory physiology, airway resistance is the resistance of the respiratory tract to airflow during inhalation and exhalation. Airway resistance can be measured using plethysmography. Definition Analogously to Ohm's Law: :R_ = \frac Where: : = P_ - P_A So: :R_ = \frac Where: *R_ = Airway Resistance *P = Pressure Difference driving airflow *P_ = Atmospheric Pressure *P_A = Alveolar Pressure *\dot V = Volumetric Airflow (not minute ventilation which, confusingly, may be represented by the same symbol) N.B. PA and \dot V change constantly during the respiratory cycle. Determinants of airway resistance There are several important determinants of airway resistance including: *The diameter of the airways *Whether airflow is laminar or turbulent Hagen–Poiseuille equation In fluid dynamics, the Hagen–Poiseuille equation is a physical law that gives the pressure drop in a fluid flowing through a long cylindrical pipe. The assumptions of the equation are that the flow is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exhalation
Exhalation (or expiration) is the flow of the breath out of an organism. In animals, it is the movement of air from the lungs out of the airways, to the external environment during breathing. This happens due to elastic properties of the lungs, as well as the internal intercostal muscles which lower the rib cage and decrease thoracic volume. As the thoracic diaphragm relaxes during exhalation it causes the tissue it has depressed to rise superiorly and put pressure on the lungs to expel the air. During forced exhalation, as when blowing out a candle, expiratory muscles including the abdominal muscles and internal intercostal muscles generate abdominal and thoracic pressure, which forces air out of the lungs. Exhaled air is 4% carbon dioxide, a waste product of cellular respiration during the production of energy, which is stored as ATP. Exhalation has a complementary relationship to inhalation which together make up the respiratory cycle of a breath. Exhalation and gas e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmospheric Pressure
Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, 760mm Hg, 29.9212 inchesHg, or 14.696psi.International Civil Aviation Organization. ''Manual of the ICAO Standard Atmosphere'', Doc 7488-CD, Third Edition, 1993. . The atm unit is roughly equivalent to the mean sea-level atmospheric pressure on Earth; that is, the Earth's atmospheric pressure at sea level is approximately 1 atm. In most circumstances, atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so atmospheric pressure decreases with increasing elevation. Because the atmosphere is thin relative to the Earth's radius—especially the dense atmospheric layer at low altitudes—the Earth's gravi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barometric
A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis to help find surface troughs, pressure systems and frontal boundaries. Barometers and pressure altimeters (the most basic and common type of altimeter) are essentially the same instrument, but used for different purposes. An altimeter is intended to be used at different levels matching the corresponding atmospheric pressure to the altitude, while a barometer is kept at the same level and measures subtle pressure changes caused by weather and elements of weather. The average atmospheric pressure on the earth's surface varies between 940 and 1040 hPa (mbar). The average atmospheric pressure at sea level is 1013 hPa (mbar). Etymology The word ''barometer'' is derived from the Ancient Greek (), meaning "weight", and (), meaning "measure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chronic Obstructive Pulmonary Disorder
Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by long-term respiratory symptoms and airflow limitation. The main symptoms include shortness of breath and a cough, which may or may not produce mucus. COPD progressively worsens, with everyday activities such as walking or dressing becoming difficult. While COPD is incurable, it is preventable and treatable. The two most common conditions of COPD are emphysema and chronic bronchitis and they have been the two classic COPD phenotypes. Emphysema is defined as enlarged airspaces (alveoli) whose walls have broken down resulting in permanent damage to the lung tissue. Chronic bronchitis is defined as a productive cough that is present for at least three months each year for two years. Both of these conditions can exist without airflow limitation when they are not classed as COPD. Emphysema is just one of the structural abnormalities that can limit airflow and can exist without airflow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lung Anatomy
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart. Their function in the respiratory system is to extract oxygen from the air and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange. Respiration is driven by different muscular systems in different species. Mammals, reptiles and birds use their different muscles to support and foster breathing. In earlier tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians. In humans, the main muscle of respiration that drives breathing is the diaphragm. The lungs also provide airflow that makes vocal sounds including human speech possible. Humans have two lungs, one on the left and one on the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
