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26 Cards in this Set
- Front
- Back
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Anatomic Dead Space
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150ml of air in the conducting airways that does not have any gas exchange with blood.
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Alverolar ventilation equation
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Does not include dead space
TV-DS = TV x Frequency= AV 500ml-150ml=350ml x15= Second TV in equation has dead space removed from it (500-150ml) |
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Total ventilation equation
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Frequency X tidal Volume= Total Ventilation
15 /min X 500ml=total vent Includes dead space |
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Tidal Volume
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500ml
Air breathing in and out regular breaths |
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Vital capacity
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Most air you can breath in and breath out. Approx 5 L
TV+ERV+IRV=VC |
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Inspiratory reserve Volume
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Max volume that can be inspired over the inspiration of a tidal volume/normal breath. Ex: Exercise/exertion
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Inspiratory Capacity
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Deepest inhalation from the exhale of your TV. Volume of maximal inspiration. IRV+TV
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Expiratory reserve volume
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Maximal volume that can be expired after the expiration of tidal volume/normal breath.
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Functional Residual Capacity
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Volume of gas remaining in lung after normal expiration. Cannot be measured by spriometry.
ERV+RV=FRC |
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What is residual volume and what is its function?
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prevents the lung from collapse at low lung volumes. Cannot be measured by lung spirometer. Can't be breathed out.
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The residual Volume
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Exhale as forcefully as you can, the remaining air in your lungs is the residual volume. Can't be measured by a spirometer.
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Physiologic Dead Space
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The volume of the lung that does not participate in gas exchange. In normal lungs, it is the same as anatomic dead space (150 ml), but may be increased in lungs with disease.
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What is Helium Gas Dilution Technique used for?
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To measure FRC. Helium is not soluable in blood. Have pt breath in helium container, the gases from the container mix with the gases from the lung (infiltrates total lung capcity). The helium become diluted by O2 and the volume of the FRC can be calculated. Obtain vital capacity - total lung capacity.
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Boyle's Law
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P X V is a constanct at constant temperature
P=pressure V=volume |
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Body plesmography
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Used when pt has trapped air.
Known pressue and volume in the box-before and after inspiration. Change in box is measured. Pressure in lungs is measured by esophgeal balloon. |
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How do we measure residual volume if there is trapped air and no cellular respiration is taking place?
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Through the body plesmography. Cellular respiration is taking place in the residual volume, except if gas is trapped. Diffusion is not taking place. Only way we can measure that is by volume/pressure relationships.
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What is alveolar ventilation and how can it be increased?
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The amount of gas available for exchange. Can be increased by increasing TV or frequency. Better off increasing TV, more efficient in healthy lungs.
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How do you measure Anatomic Dead Space?
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Fowlers method- as you exhale, you get more and more nitrogen coming out (inital air coming out of lungs is 100% O2 coming from conducting airways because there was no gas exchange happening). Finally, you have an even exchange with alveolar plateau (gas that has been exchanged in resp zone).
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How do you measure Physiologic Dead Space?
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Bohr's Method: Measuring physiologic Dead space because it measures the volume of lung that does not eliminate CO2. If there is a pumonary embolism (example) blocking blood flow (via capiliary) by the alveoli, then there is no ETCO2 (expired CO2) coming out.
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Physiologic Dead Space Equation
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Anatomic Dead Space + Alveolar Dead Space=PDS
Bohr's Method |
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Which zones ventilate better?
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Lower zones have higher ventilation per unit volume.
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When a subject lies in the supine position....
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the posterior lung, ventilates more than the anterior lung.
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When a subject lies in the lateral position...
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the dependent lung is best ventilated (per unit volume).
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Why is the dependent lung better ventilated?
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Alveoli at the baseof the lung are compressed (smaller), when you breath, they gain more volume than the upper alveoli which are already more inflated. The lower alveoli GAIN more volume than the upper therefore the lower are better ventilated per unit volume.
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Why does CO2 diffuse more rapidly through tissues? (as described by Fick's Law)
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CO2 diffuses much more rapidly than O2 because it is a much more soluable gas. The area of the blood-gas barrier in the lung is large and thin.
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Factors affecting Pulmonary diffusion
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1) changes in the effective surface area of gas exchange.
Ex: Is the lung damaged? 2) changes related to the uptake of gases by the RBC Ex: Is it fetal or sickle cell Hemeoglobin? CO posion? 3) Change in the physical properties of the membrane. Ex: Is something in the way of the diffusion pathway (the alveolar capillary interface) such as pulmonary fibrosis |
