Term
| Calculating rate of flow in pulmonary circulation |
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Definition
| Q=ΔP (gradient of pulm artery – left atrium)/R |
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Term
| Characteristics of pulmonary circulation and flow |
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Definition
Low pressure and resistance.
High capacity, vessels can distend; can also recruit new vessels in times of strenuous activity.
Have compliant vessels, thin walled with little smooth muscle.
PVR low due to large number of dilated vessels. |
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Term
| Passive influences of pulmonary vascular bed |
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Definition
1. CO
2. Body position
3. Changes in lung volume
4. Alveolar pressure
5. Left atrial pressure |
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Term
| Active influences on pulmonary vascular bed |
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Definition
1. Autonomic stimulation
2. Hormonal/chemical stimulation
3. Alveolar hypoxemia and hypercapnea |
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Term
| Pulmonary Response to Cardiac Output (CO) |
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Definition
Resistance decreases with increasing CO
Increased recruitment of vessels.
Increased dilation/distension of vessels.
Net result: Reduces pulmonary edema
Reduces RV workload
Increases capillary surface area
Maintains transit time of blood flow. |
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Term
| Pulmonary response to alveolar pressure |
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Definition
Alveolar vessels in lungs are next to alveoli and can be pinched and stretched when alveoli expand with air.
The stretching created by the alveoli (radial traction) can then increase the caliber of extra-alveolar vessels. |
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Term
| Differences in regulation of systemic and pulmonary system |
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Definition
1. Hormones and neurotransmitters play a minimal role in pulmonary system.
2. Hypoxia, Hypercapnea, and acidosis creates vasoconstriction in pulmonary system instead of vasodilation. |
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Term
| PAO2 effect on pulmonary system |
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Definition
Major factor regulating pulmonary blood flow
↓ PAO2 causes vasoconstriction
Hypoxic vasoconstriction: Adaptive mechanism to reduce blood flow to poorly ventilated/oxygenated alveoli and direct to areas well-ventilated where gas exchange would be better
Prolonged hypoxia can lead to chronic changes in vasculature and pulmonary HTN, with right ventricle hypertrophy.
Mechanism of this response is poorly understood: lower levels of PAO2 “sensed” → depolarized smooth muscle → CA+2 enters → vasoconstriction
Nitric oxide (NO) synthesized in endothelial cell →cGMP →smooth muscle relaxation |
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Term
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Definition
| Vasocontricter, released in times of lung injury |
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Term
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Definition
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Term
| Forces that affect fluid flow in pulmonary capillaries |
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Definition
1. Hydrostatic
2. Oncotic
3. Inward pull resulting from alveolar surface tension
4. Alveolar pressure compresses the interstitum and favors movement of solutes into capillary |
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Term
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Definition
Where filtration is greater than fluid removal in pulmonary capillaries, results in fluid in lung.
1. Heart failure increases capillary hydrostatic pressure
2. Lung injury increases capillary permeability
3. ARDS increases surface tension
4. Decreased plasma oncotic pressure in starvation. |
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