37 Pathophysiology of Pulmonary Vascular Disease Flashcards
1
Q
Pulmonary vascular disease
- Characterized by…
- This causes…
- Can be caused by disorders that…
A
- 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
Q
Intrinsic pulmonary vascular disease
A
- Idiopathic pulmonary arterial hypertension
- Chronic thromboembolic pulmonary hypertension
- Pulmonary hypertension associated with collagen vascular diseases
- HIV
- Left to right shunts
3
Q
Alterations in respiratory mechanics
A
- Intrinsic pulmonary vascular disease does not affect the pulmonary parenchyma or the airways
- Elastic recoil, compliance, and airway resistance are typically normal
4
Q
Alterations in gas exchange:
Narrowing or occlusion of pulmonary arteries leads to…
A
- Redistribution of pulmonary blood flow
- An abnormally large degree of mismatching between ventilation and perfusion
5
Q
Alterations in gas exchange:
V/Q regions, PaO2, minute ventilation, and PaCO2
- V/Q regions
- PaO2 and PA-aO2
- Minute ventilation and PaCO2
A
- 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)
- These diseases produce high V/Q regions
- 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
Q
Alterations in gas exchange
- PaO2 with exercise
- The mechanism
A
- 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
- With a large decrease in the surface area available for diffusion, exercise causes…
7
Q
Pulmonary function tests
- Lung and chest wall mechanics
- Lung volumes and flow rates
- PFT findings
- DLCO
- Surface area of the alveolar-capillary interface
A
- 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
Q
Alterations in cardiovascular function
- Pulmonary vascular disease causes…
- This can lead to…
- …which is manifested clinically by…
A
- 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
Q
Alterations in cardiovascular function
- Right ventricular failure can reduce left ventricular output in two ways
- Both of these processes…
A
- 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
Q
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…
A
- 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