Term
| the mass movement of air in and out of the lungs occurs because... |
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Definition
| transpulmonary and transairway pressure changes generated by the action of the diaphragm. this mechanism carries oxygen from the atmosphere to the alveoli and carbon dioxide from the alveoli to the external environment. |
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Definition
| ventilation moves gases from one point to another (eg from the atmosphere to the alveoli); it does not move gas molecules across the alveolar-capillary membrane. |
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Definition
| the movement of gas molecules from an area of relatively high concentration of gas to one of low concentration. continues until all the gases in the two areas are in equilibrium. |
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Definition
the behavior of gases surrounding the earth. gas constant has a fixed value of 0.0821. P1 X V1 = P2 X V2 T1 T2 |
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Definition
if temperature remains constant, pressure will vary inversely to volume (P1 X V1 = P2 X V2) |
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Definition
if pressure remains constant, volume and temperature will vary directly V1 = V2 T1 T2 |
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Definition
if the volume remains constant, pressure and temperature will vary directly. P1 = P2 T1 T2 |
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Definition
| in a mixture of gases, the total pressure is equal to the sum of the partial pressures of each seperate gas. the pressure produced by a particular gas is completely unaffected by the presence of another gas. |
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Definition
| the atmospheric gases that surround the earth exert a force on the earth's surface. at sea level is about 760 mm Hg and is a function of Dalton's law. decreases with an increase in altitude. |
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Term
| Partial pressures of Oxygen and carbon dioxide |
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Definition
| by the time the oxygen molecules reach the alveoli, they are diluted by the addition of CO2 and H2O molecules. this leads to a decrease in the partial pressure of oxygen in the alveoli (PAO2) |
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Term
ideal alveolar gas equation |
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Definition
alveolar oxygen tension PAO2 can be computed as follows: PAO2 = [PB - PH2O] FIO2 - PaCO2 (1.25) 1.25 is a factor that adjusts for alterations in oxygen tension due to variations in the respiratory exchange ratio (RR), which is the ratio of the amount of oxygen that moves into the pulmonary capillay blood to the amount of carbon dioxide that moves out of the pulmonary blood and into the alvioli. |
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Term
| Simplified alveolar gas equations |
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Definition
may be used clinically when the PaCO2 is less than 60 mmHg, and when the patient is receiving oxygen therapy greater than 0.6: PAO2 = [PB - PH2O] FIO2 - PaCO2 |
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Term
| alveolar capillary membrane is composed of |
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Definition
- the liquid lining the intra-alveolar membrane
- the alveolar epithelial cell
- the basement membrane of the alveolar epithelial cell
- loose connective tissue (the interstitial space)
- the basement membrane of the capillary endothelium
- the capillary endothelium
- the plasma in the capillary blood
- the erythrocyte membrane, and
- the intracellular fluid in the erythrocyte until a hemoglobin molecule is encountered
The thickness of these physical barriers is between 0.36 and 2.5 micrometers |
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Term
venous blood entering the alveolar-capillary system |
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Definition
| in the healthy resting individual has an average oxygen tension (PVO2) of 40 mmHg, and an average carbon dioxide tension (PVCO2) of 46 mmHg. as blood passes through the capillary, the average alveolar oxygen tension (PACO2) is 100 mmHg. |
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Definition
the rate of gas transfer across a sheet of tissue is directly proportional to the surface area of the tissue, to the diffusion constants, and to the difference in partial pressure of the gas between the two sides of the tissue, and is inversely proportional to the thickness of the tissue. |
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Definition
| the amount of gas that dissolves in a liquid at a given temperature is proportional to the partial pressure of the gas. |
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Term
| solubility coefficient of a liquid |
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Definition
The amount of gas that can be dissolved by 1 mL of a given liquid at standard pressure (760 mmHg) and specified temperature varies inversely with temperature. |
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Definition
| the rate of diffusion of a gas through a liquid is 1) directly proportional to the solubility coefficient of the gas and 2) inversely proportional to the square root of the gram-molecular weight (GMW) of the gas. |
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Definition
| the transfer of gas across the alveolar wall is a funtion of the amount of blood that flows past the alveoli. |
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Definition
| the movement of gas across the alveolar wall is a function of the integrity of the alveolar-capillary membrane itself. |
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Term
diffusion capacity of carbon monoxide (DLCO) |
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Definition
| test that measured the amount of CO that moves across the alveolar capillary membrane into the blood in a given time. |
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Term
| diffusion-limited problems |
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Definition
- alveolar collapse (atelectasis)
- thickening of alveolar wall (alveolar fibrosis)
- alveolar consolidation (pneumonia)
- frothy secretions (pulmonary edema)
- alveolar-capillary destruction (emphysema)
- interstential edema
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Term
| Measures that affect measured DLCO |
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Definition
- Age
- Lung volume
- body size
- body position
- exercise
- alveolar PO2 (PAO2)
- hemoglobin concentration
- carboxyhemoglobin
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