37 Pathophysiology of Pulmonary Vascular Disease Flashcards Preview

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Flashcards in 37 Pathophysiology of Pulmonary Vascular Disease Deck (10):
1

Pulmonary vascular disease

  • Characterized by...
  • This causes...
  • Can be caused by disorders that...

  • Characterized by...
    • Narrowing or occlusion of the pre-capillary pulmonary arteries
  • This causes...
    • An increase in pulmonary vascular resistance, which leads to an abnormally high pulmonary artery pressure (pulmonary hypertension)
  • Can be caused by disorders that...
    • Affect only the pulmonary vasculature (intrinsic)
    • Result from diseases that damage the airways and/or parenchyma of the lungs (extrinsic)

2

Intrinsic pulmonary vascular disease

  • Idiopathic pulmonary arterial hypertension
  • Chronic thromboembolic pulmonary hypertension
  • Pulmonary hypertension associated with collagen vascular diseases
  • HIV
  • Left to right shunts

3

Alterations in respiratory mechanics

  • Intrinsic pulmonary vascular disease does not affect the pulmonary parenchyma or the airways
  • Elastic recoil, compliance, and airway resistance are typically normal

4

Alterations in gas exchange:
Narrowing or occlusion of pulmonary arteries leads to...

  • Redistribution of pulmonary blood flow
  • An abnormally large degree of mismatching between ventilation and perfusion

5

Alterations in gas exchange:
V/Q regions, PaO2, minute ventilation, and PaCO2

  • V/Q regions
  • PaO2 and PA-aO2
  • Minute ventilation and PaCO2

  • V/Q regions
    • These diseases produce high V/Q regions
      • Since blood flow is decreased or stopped to lung units that remain normally ventilated
    • This blood must be diverted to other regions of the lungs, which will then have too much perfusion for the amount of ventilation (i.e. low V/Q)
  • PaO2 and PA-aO2
    • The low V/Q units will cause the PaO2 to fall and the PA-aO2 to increase
  • Minute ventilation and PaCO2
    • High V/Q units increase the amount of alveolar and physiologic dead space
    • This increases the minute ventilation required to maintain a normal PaCO2
    • Patients with pulmonary vascular disease usually increase minute ventilation so that PaCO2 remains normal or even decreases

6

Alterations in gas exchange

  • PaO2 with exercise
  • The mechanism 

  • PaO2 with exercise
    • Like emphysema and interstitial lung disease, disorders of the pulmonary vasculature are often associated with a fall in PaO2 with exercise
  • The mechanism
    • With a large decrease in the surface area available for diffusion, exercise causes...
      • An increase in capillary blood velocity
      • A decrease in the time available for equilibration between the PaO2 of alveolar gas and capillary blood

7

Pulmonary function tests

  • Lung and chest wall mechanics
  • Lung volumes and flow rates
  • PFT findings
  • DLCO
  • Surface area of the alveolar-capillary interface

  • Lung and chest wall mechanics
    • Intrinsic pulmonary vascular disease does not alter lung or chest wall mechanics
  • Lung volumes and flow rates
    • Lung volumes and flow rates measured by pulmonary function testing are usually normal
  • PFT findings
    • Patients with pulmonary vascular damage from parenchymal lung disease will, of course, have PFT findings typical of the underlying disease
  • DLCO
    • Both intrinsic and extrinsic pulmonary vascular diseases reduce the DLCO
  • Surface area of the alveolar-capillary interface
    • This is because vascular narrowing and occlusion decrease the surface area of the alveolar-capillary interface

8

Alterations in cardiovascular function

  • Pulmonary vascular disease causes...
  • This can lead to...
  • ...which is manifested clinically by...

  • Pulmonary vascular disease causes...
    • Pulmonary hypertension
  • This can lead to...
    • Increased right ventricular afterload
    • Right ventricular failure
  • ...which is manifested clinically by...
    • Peripheral edema
    • Hepatomegaly
    • Jugular venous distention

9

Alterations in cardiovascular function

  • Right ventricular failure can reduce left ventricular output in two ways
  • Both of these processes...

  • Right ventricular failure can reduce left ventricular output in two ways
    • Impaired RV systolic function reduces the amount of blood pumped to the left heart
    • RV dilation, when severe, can reduce LV size and compliance
  • Both of these processes...
    • Reduce LV preload, which can lead to a drop in cardiac output and even hypotension

10

Pathophysiology of dyspnea and exercise intolerance

  • Intrinsic pulmonary vascular disease leads to symptoms primarily through its effects on...
  • With increased activity, cardiac output and blood flow through the lungs...
  • Since vascular resistance is high, this leads to...
  • RV dysfunction leads to...

  • Intrinsic pulmonary vascular disease leads to symptoms primarily through its effects on...
    • Cardiovascular function
  • With increased activity, cardiac output and blood flow through the lungs...
    • Increases
  • Since vascular resistance is high, this leads to...
    • A further increase in pulmonary artery pressure
    • Increased RV afterload
    • Precipitated or worsened RV failure
  • RV dysfunction leads to...
    • Inadequate LV preload
    • Prevention of cardiac output from increasing sufficiently to meet the metabolic demands of the body
    • Dyspnea and exercise intolerance

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