Pulmonary Oedema Flashcards
What is the difference between wheeze and crepitations in terms of their underlying pathological basis?
Wheeze is caused by airway pathology
Crepitations are caused by pathology (fluid or fibrosis) at the level of the terminal bronchioles and alveoli
What 5 signs can be seen on a CXR with pulmonary oedema caused by AMI?
Cardiomegaly
Upper lobe venous congestion
Dilated interlobular septa (Kerley b lines)
Perihilar alveolar opacities
Fluid in fissures and costophrenic spaces
What causes increased capillary fluid loss following AMI?
Increased Pc
What mechanical changes to lung function occur in pulmonary oedema?
Decreased lung compliance (increases elastic WOB)
Decreased lung volumes (restrictive defect, increases elastic WOB)
Increased airway resistance (increases resistive WOB)
What changes occur to lung function in pulmonary oedema?
Mechanical changes
Impaired gas exchange (shunt and low V/Q units)
Arterial blood gases imbalance
Increased pulmonary vascular resistance
How can hypoxaemia cause metabolic acidosis?
Hypoxaemia and decreased CO due to LHF results in decreased tissue O2 delivery
Decreased tissue O2 delivery causes increased anaerobic metabolism by tissues
Lactic acid is produced and causes a metabolic acidosis
What is the effect of interstitial and alveolar oedema on lung function, respectively?
Interstitial: increases WOB but does not cause severe gas exchange abnormality
Alveolar: significant effect on gas exchange
What are the major causes of pulmonary oedema?
Increased Pc
Increased capillary permeability
(decreased Oc and lymphatic drainage can be exaggerating factors)
Give some examples of conditions which increase Pc and can lead to pulmonary oedema
LV dysfunction
Mitral stenosis
Give some examples of conditions which increase capillary permeability and can lead to pulmonary oedema
Toxins
Sepsis
Multiple trauma
Aspiration of gastric acid
