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22 Cards in this Set

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What is surfactant composed of?
1. Dipalmityl phosphatidylcholine(lecithin)major component
2. Phosphatidylglycerol
3. Other lipids
4. Neutral lipids
5. Proteins
What are the functions of pulmonary surfactant?
Reduce surface tension at low lung volumes(prevents atalectasis)
Increase surface tension
Increase alveolar radius
Reduce pulmonary capillary infiltration
Which cells produce surfactant?
Type 2 alveolar epithelial cells
List 6 ways that surfactant synthesis may be reduced?
1. Developmental deficiency
2. Hypovolemia
3. Hypothermia
4. Acidosis
5. Hypoxemia
6. rare genetic disorders
What is the significance of surfactant in infant respiratory distress syndrome(IRDS)?
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.
What does the therapy for IRDS include?
1. Positive end expiratory pressure(PEEP)
2. Exogenous surfactant
3. Steroids
By what week do the fetal lungs make surfactant?
Week 34-36
What may indicate fetal pulmonary maturity?
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.
What L/S ratio uaually pulmonary maturity?
2:1
What can be used to help accelerate the maturation of surfactant in the lungs of a fetus?
Glucocorticoid hormones
How are individual alveoli prevented from collapsing normally?
Alveolar walls and airway walls are structurally connected so that tension on adjacent walls created by collapsing an alveolus holds it open.
What factors determine airway resistance?
Rate of gas flow through the airway
Diameter of the airway
Length of the airway
What law describes airway resistance?
Poiseuilles law

R= 8nl
______
3.14r4(pieX radius to 4th power)
R= resistance, n= viscosity of inspired gas, l= length of airway, r= radius
How are airway resistance and airflow related?
Inversely:

Q=AP(pressure gradient)
____
R (airway resistance0
Which part of the respiratory system is the major site of airway resistance?
Medium sized bronchi
Which part of the respiratory system has the highest individual resistance?
Small terminal airways(they are not the major site of airway resistance due to their parallel arrangement).
Which factors can change airway resistance?
1. Altering the radius of the airways
2. Changes in lung volume
3. Viscosity/density of the inspired gas
What causes bronchoconstriction?
Parasympathetic discharge
Substance P
Adenosine
Hypersensitivity response(histamines)
Arichadonic acid metabolites(prostaglandins and leukotrienes.
How does bronchoconstriction affect airways?
Reduces airway radius
Increases resistance
Limits airflow during inspiration or expiration
What causes bronchodilation?
Sympathetic discharge and sympathetic agonists via beta 2 receptors
How do obstructive diseases affect respiratory mechanics?
Increase airway resistance
How do restrictive diseases affect respiratory mechanics?
Decrease compliance.