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11 Cards in this Set
- Front
- Back
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What is Poiseuille's law?
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Q = ΔPxπR^4 / 8Lη
R is the internal radius of the tube (meters) ΔP is the pressure difference between the two ends (pascals) η is the dynamic fluid viscosity (pascal-second (Pa·s)), L is the total length of the tube in the x direction (meters). |
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Compare resistance to airflow during inspiration vs during expiration
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Resistance to air-flow is greater on expiration than on inspiration. This is because on inspiration, the bronchioles distend (increased radius) which decreases resistance. The opposite happens on expiration, and is pronounced in emphesema, forced expirations.
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How does gravity affect the diameter of the airways?
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The weight of the lungs compresses the lower lobes by about 7cm H2O more than the upper lobes; thus the lower lobes open later on inspiration.
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How does air distribute amongst the lung lobes at different volumes of respiration?
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Starting inspiration from RV, most air enters the upper lobes, but once you reach FRC most air goes to the lower lobes. Because you normally breathe above FRC, the lower lobes are usually better ventilated than the upper lobes.
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Describe the molecular events of of bronchoconstriction
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CNS --> PSNS stimulation --> ACh : Musc. Receptors --> GTP -> cGMP --> Bronchiolar constriction
Many other agents can cause this, such as histamines, leukotrienes, prostaglandins, bradykinin, NO, cytokines, etc. |
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Describe the molecular events involved in bronchodilation
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Epi -> beta-2 receptor --> ATP->cAMP --> bronchiolar dilation
Other drugs (like albuterol) also act selective on the beta2 receptor |
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Describe autoregulation of alveolar ventilation in the context of a pulmonary embolus blocking a pulmonary arteriole
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The PE causes histamine release and a decrease in alveolar CO2 tension (PACO2) --> this causes alveolar ducts to constrict and shunt air from the nonperused alveoli more well perfused alveoli.
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What is the purpose of alveolar autoregulation?
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Minimizes physiological dead space
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What are the normal FEV1, FVC, and FEV1/FVC ratio values?
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FEV1 = 3.3L
FVC = 4.0L FEV1/FVC = 83% A person should be able to breathe out 83% of their vital capacity in one second. A person with interstitial fibrosis has a normal FEV1/FEV. |
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Compare the effort-dependence of expiration at high and low lung volumes. What plot can be used to demonstrate this?
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Expiration is effort dependent at high lung volumes, but effort independent at low lung volumes. This can be graphed on a Flow vs Lung Volume curve, with a patient expiring at different levels of effort.
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Describe the flow vs. lung volume curves for normal people, patients with emphysema, and patients with interstitial fibrosis
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Patients with emphysema and IF fall on opposite ends of normal flow volume curves. In emphysema, the TLC is greater than normal, the velocity of flow is low, the curve has a scooped out appearance, and the RV is high. In IF, the TLC is less than normal, the velocity is grater than normal, and the RV is low.
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