32 Pathophysiology of Air Space Filling Diseases Flashcards Preview

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Flashcards in 32 Pathophysiology of Air Space Filling Diseases Deck (6)
1

Airspace filling diseases

  • Characterized by...
  • Most commonly...

  • Characterized by...
    • The replacement of alveolar gas with some type of “foreign” material
  • Most commonly...
    • Edema fluid (pulmonary edema)
    • Inflammatory cells (pneumonia)
    • Blood (alveolar hemorrhage)

2

Airspace filling diseases:
Alterations in respiratory mechanics

  • Lung volumes are reduced in these diseases simply because there are fewer “empty” alveoli to receive the inspired gas
  • In a sense, then, airspace filling diseases produce small lungs by markedly reducing the number of available alveoli

3

Airspace filling diseases:
Alterations in gas exchange

  • These diseases interfere with...
  • What occurs since perfusion remains relatively intact
  • Depending on disease severity, a variable proportion of the lungs receives...
  • For example, in patients with severe ARDS,...

  • These diseases interfere with ventilation to affected alveoli
  • Since perfusion remains relatively intact (even with hypoxic vasoconstriction), a marked increase in V/Q mismatching occurs, with low V-Q ratios predominating
  • Depending on disease severity, a variable proportion of the lungs receives no ventilation, and this produces a right to left shunt
  • For example, in patients with severe ARDS, as much as 50% of the cardiac output may pass through unventilated alveoli

4

Airspace filling diseases:
Alterations in gas exchange

  • The presence of V/Q mismatching and shunt causes...
  • As always, V/Q mismatching also produces...
  • The reduction in the number of gas-filled alveoli cause...
  • This leads to...

  • The presence of V/Q mismatching and shunt causes PaO2 to fall and PA-aO2 to increase
  • As always, V/Q mismatching also produces high V/Q regions, which increase alveolar and physiologic dead space
  • The reduction in the number of gas-filled alveoli cause the tidal volume to fall
  • This leads to an increase in VD/VT and to a further increase in dead space ventilation
  • Patients are usually able to compensate for these changes by increasing minute ventilation
  • In those with diffuse alveolar filling (e.g. ARDS, pulmonary edema) such an increase may not be possible due to a marked increase in dead space ventilation, and these patients may develop acute hypercapnia

5

Airspace filling diseases:
Alterations in gas exchange

  • Patients are usually able to...
  • In those with diffuse alveolar filling (e.g. ARDS, pulmonary edema),...

  • Patients are usually able to compensate for these changes by increasing minute ventilation
  • In those with diffuse alveolar filling (e.g. ARDS, pulmonary edema), such an increase may not be possible due to a marked increase in dead space ventilation, and these patients may develop acute hypercapnia

6

Airspace filling diseases:
Pathophysiology of dyspnea and exercise intolerance

  • In the airspace filling diseases, these symptoms result primarily from alveolar filling, which reduces tidal volume and forces the respiratory rate to increase
  • Other factors include increased physiologic dead space and arterial hypoxemia

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