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22 Cards in this Set
- Front
- Back
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What is surfactant composed of?
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1. Dipalmityl phosphatidylcholine(lecithin)major component
2. Phosphatidylglycerol 3. Other lipids 4. Neutral lipids 5. Proteins |
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What are the functions of pulmonary surfactant?
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Reduce surface tension at low lung volumes(prevents atalectasis)
Increase surface tension Increase alveolar radius Reduce pulmonary capillary infiltration |
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Which cells produce surfactant?
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Type 2 alveolar epithelial cells
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List 6 ways that surfactant synthesis may be reduced?
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1. Developmental deficiency
2. Hypovolemia 3. Hypothermia 4. Acidosis 5. Hypoxemia 6. rare genetic disorders |
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What is the significance of surfactant in infant respiratory distress syndrome(IRDS)?
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There is a surfactant deficiency which results in high surface tension in the lungs, as well as many areas of atelectasis. There is also decreased FRC and subsequent arterial hypoxemia.
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What does the therapy for IRDS include?
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1. Positive end expiratory pressure(PEEP)
2. Exogenous surfactant 3. Steroids |
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By what week do the fetal lungs make surfactant?
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Week 34-36
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What may indicate fetal pulmonary maturity?
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The ratio of Lecithin concentration(increases with maturity) to sphingomyelin(which remains constant during gestation) or L/S ratio in the amniotic fluid. The presence of minor phosphalipids(phosphatidylglycedrol) is also indicative in cases where the L/S ratio is borderline.
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What L/S ratio uaually pulmonary maturity?
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2:1
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What can be used to help accelerate the maturation of surfactant in the lungs of a fetus?
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Glucocorticoid hormones
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How are individual alveoli prevented from collapsing normally?
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Alveolar walls and airway walls are structurally connected so that tension on adjacent walls created by collapsing an alveolus holds it open.
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What factors determine airway resistance?
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Rate of gas flow through the airway
Diameter of the airway Length of the airway |
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What law describes airway resistance?
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Poiseuilles law
R= 8nl ______ 3.14r4(pieX radius to 4th power) R= resistance, n= viscosity of inspired gas, l= length of airway, r= radius |
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How are airway resistance and airflow related?
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Inversely:
Q=AP(pressure gradient) ____ R (airway resistance0 |
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Which part of the respiratory system is the major site of airway resistance?
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Medium sized bronchi
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Which part of the respiratory system has the highest individual resistance?
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Small terminal airways(they are not the major site of airway resistance due to their parallel arrangement).
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Which factors can change airway resistance?
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1. Altering the radius of the airways
2. Changes in lung volume 3. Viscosity/density of the inspired gas |
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What causes bronchoconstriction?
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Parasympathetic discharge
Substance P Adenosine Hypersensitivity response(histamines) Arichadonic acid metabolites(prostaglandins and leukotrienes. |
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How does bronchoconstriction affect airways?
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Reduces airway radius
Increases resistance Limits airflow during inspiration or expiration |
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What causes bronchodilation?
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Sympathetic discharge and sympathetic agonists via beta 2 receptors
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How do obstructive diseases affect respiratory mechanics?
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Increase airway resistance
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How do restrictive diseases affect respiratory mechanics?
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Decrease compliance.
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