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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.
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 concentration of carbon dioxide (CO 2) rises in the blood when the metabolic use of oxygen (O 2), and the production of CO 2 is increased during, for example, exercise. The CO 2 in the blood is transported largely as bicarbonate (HCO 3 − ) ions, by conversion first to carbonic acid (H 2 CO 3 ), by the enzyme carbonic anhydrase , and then ...
At the end of inspiration, the alveolar pressure returns to atmospheric pressure (zero cmH 2 O). [2] During exhalation, the opposite change occurs. The lung alveoli collapse before air is expelled from them. The alveolar pressure rises to about +1 cmH 2 O. This forces the 500 ml of inspired air out of the lung during the 2–3 seconds of ...
Minute ventilation (or respiratory minute volume or minute volume) is the volume of gas inhaled (inhaled minute volume) or exhaled (exhaled minute volume) from a person's lungs per minute. It is an important parameter in respiratory medicine due to its relationship with blood carbon dioxide levels .
The most common gas tensions measured are oxygen tension (P x O 2), carbon dioxide tension (P x CO 2) and carbon monoxide tension (P x CO). [3] The subscript x in each symbol represents the source of the gas being measured: "a" meaning arterial, "A" being alveolar, "v" being venous, and "c" being capillary. [3] Blood gas tests (such as arterial ...
Maximum inspiratory pressure is an important and noninvasive index of diaphragm strength and an independent tool for diagnosing many illnesses. [29] Typical maximum inspiratory pressures in adult males can be estimated from the equation, M IP = 142 - (1.03 x Age) cmH 2 O, where age is in years. [30]
TLC: Total lung capacity: the volume in the lungs at maximal inflation, the sum of VC and RV. TV: Tidal volume: that volume of air moved into or out of the lungs in 1 breath (TV indicates a subdivision of the lung; when tidal volume is precisely measured, as in gas exchange calculation, the symbol TV or V T is used.)