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Image illustrating transpulmonary, intrapleural and intra-alveolar pressure. Alveolar pressure (P alv) is the pressure of air inside the lung 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 cmH 2 O. [1] [2]
Alveolar pressure (PA) at end expiration is equal to atmospheric pressure (0 cm H 2 O differential pressure, at zero flow), plus or minus 2 cm H 2 O (1.5 mmHg) throughout the lung. On the other hand, gravity causes a gradient in blood pressure between the top and bottom of the lung of 20 mmHg in the erect position (roughly half of that in the ...
The alveolar oxygen partial pressure is lower than the atmospheric O 2 partial pressure for two reasons. Firstly, as the air enters the lungs, it is humidified by the upper airway and thus the partial pressure of water vapour (47 mmHg) reduces the oxygen partial pressure to about 150 mmHg.
The alveolar pressure is estimated by measuring the pressure in the airways while holding one's breath. [2] The intrapleural pressure is estimated by measuring the pressure inside a balloon placed in the esophagus. [2] Measurement of transpulmonary pressure assists in spirometry in availing for calculation of static lung compliance.
Image illustrating transpulmonary, intrapleural and intra-alveolar 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. [1]
Fig. 4 Atmospheric pressure. Atmospheric pressure decreases with the height above sea level (altitude) and since the alveoli are open to the outside air through the open airways, the pressure in the lungs also decreases at the same rate with altitude. At altitude, a pressure differential is still required to drive air into and out of the lungs ...
The alveolar air pressure is therefore always close to atmospheric air pressure (about 100 kPa at sea level) at rest, with the pressure gradients because of lungs contraction and expansion cause air to move in and out of the lungs during breathing rarely exceeding 2–3 kPa. [18] [19] During exhalation, the diaphragm and intercostal muscles relax.
Positive end-expiratory pressure (PEEP) is the pressure in the lungs (alveolar pressure) above atmospheric pressure (the pressure outside of the body) that exists at the end of expiration. [1] The two types of PEEP are extrinsic PEEP (PEEP applied by a ventilator) and intrinsic PEEP (PEEP caused by an incomplete exhalation).