Pulmonary Embolism And Respiratory Failure

Question 1

What is embolism?

Answer 1

Obstruction of blood vessel by solid liquid or gas travelling in the bloodstream lodging within the blood vessel.

Question 2

Where do most pulmonary embolisms arise from?

Answer 2

Deep vein thrombosis of popliteal vein or pelvic veins

Question 3

What is Virchows triad?

Answer 3

Endothelial injury,
Stasis or turbulent blood flow,
Blood hypercoagulability.

Question 4

What risk factors are there for thromboembolism?

Answer 4

Pregnancy,
Prolonged immobility,
Oral contraceptive pill,
Cancer,
Obesity,
Surgery.

Question 5

How does PE lead to acute right ventricle overload?

Answer 5

Dramatic pressure increase in pulmonary arteries leading to right ventricular dilatation and strain. Positive inotropes released to combat this cause vasoconstriction and further exacerbate the situation.

Question 6

What other risks are patients with a patent foramen ovale at risk of with PE?

Answer 6

Right to left shunting, severe hypoxaemia and paradoxical embolism leading to strokes

Question 7

What 3 main pathological clinical outcomes are there for PE?

Answer 7

Respiratory failure,
Pulmonary infarction,
Acute right sided heart failure.

Question 8

What are common symptoms of PE?

Answer 8

Dyspnea,
Pleuritic chest pain,
Cough,
Haemoptysis.

Question 9

What are common signs of PE?

Answer 9

Tachypnea,
Decreased breath sounds,
Tachycardia,
Fever,
Diaphoresis (excessive sweating).

Question 10

What differential diagnoses may there be for PE?

Answer 10

Pneumothorax,
Pneumonia,
MI,
Pericarditis,
Pleurisy,
Musculoskeletal chest pain.

Question 11

What investigations should be carried out for PE?

What would you see?

Answer 11

Blood gases - hypoxaemia and hypocapnea,
CXR - often normal in PE or peripheral wedge shaped opacificafion.
ECG - right ventricular strain
D-dimer

Question 12

What classic finding indicates PE on ECG?

Answer 12

S1 Q3 T3 - deep S wave in lead 1, Q wave in lead 3 and inverted T wave in lead 3.

Question 13

What is wells score?

Answer 13

System for estimating probability of DVT and PE. A score of more than 4 indicates likely PE

Question 14

What imaging can be done to look for PE?

Answer 14

CT pulmonary angiography

Question 15

What is the treatment plan for PE?

Answer 15

Oxygen ASAP,
Immediate subcutaneous low molecular weight heparin,
Start on oral anticoagulant eg rivaroxaban for 3 months if identifiable cause or indefinitely if malignancy.

Question 16

What prevention strategies exist for DVT?

Answer 16

Compression stockings,
Mobilise patients after surgery,
DVT prophylactic anticoagulants.

Question 17

What characterises the 1 respiratory failure?

Answer 17

Low PaO2 and normal or low PaCO2.

Gas exchange impaired at alveolar-capillary membrane.

Question 18

What characterises type 2 respiratory failure?

Answer 18

Low PaO2 and high PaCO2.

Reduced ventilators effort (hypoventilation)

Question 19

What are the effects of hypoxaemia?

Answer 19

Tachypnaea,
Tachycardia,
Confusion and irritation,
Central cyanosis

Question 20

What are the causes of hypoxaemia?

Answer 20

1. Low inspired pO2
2. Ventilation perfusion mismatch
3. Diffusion defect
4. Intra-lung shunt
5. Hypoventilation