Flashcards in 32 Pathophysiology of Air Space Filling Diseases Deck (6)
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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)
- The replacement of alveolar gas with some type of “foreign” material
- 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
