Lung diseases and Allergology
1. Pulmonary embolism
Definitions:
Pulmonary Embolism (PE) – obstruction of the lumen of one or more pulmonary arteries. Most
often due to blood thrombi from deep vein thrombosis DVT that dislodge and become emboli.
Venous Thromboembolism (VTE) – umbrella term that includes PE + DVT
o Recurrent VTE – VTE that recurs in a patient after completing 2 weeks of antithrombotic
therapy.
o Provoked VTE – VTE in a person with one or more risk factors for VTE
o Unprovoked (idiopathic) VTE – in an individual without any risk factors.
Epidemio:
Increasing incidence with age
Overall more common in males, but females have a slight increase during reproductive years.
Etiology:
DVT is the most common cause
Other causes – fat embolism (after major surgery)
Air embolism, amniotic fluid embolism, tumor emboli
Risk Factors:
o Pregnancy
o Major surgeries
o Varicose veins
o Oral contraceptives
o Bed rest or inactivity
o Heart disease or prior DVT
Pathophysio:
Thrombus formation DVT in the legs or pelvis, most common is the iliac vein embolization to
pulmonary arteries via the inferior vena cava partial or complete obstruction of pulmonary
arteries.
Response of the lung to arterial obstruction:
o Pleuritic pain + hemoptysis
o Surfactant dysfunction atelectasis decreased oxygen sat
o Triggers resp drive hyperventilation, tachypnea resp alkalosis with hypocapnia
o Impaired gas exchange arterial hypoxemia
o Cardiac compromise
Increased pulmonary artery pressure (PAP) due to blockage right ventricular
pressure overload forward failure with decreased cardiac output hypotension
and tachycardia.
o Pulmonary vasoconstriction – via thromboxane A2, prostaglandins, adenosine, thrombin and
serotonin secreted by activated platelets and the thrombus pulmonary vasoconstriction
and bronchospasm.
, Clinical Features:
Acute onset of symptoms, triggered by specific event usually standing up in the morning, physical
exercise
Dyspnea, Tachypnea - >50%
Sudden pleuritic chest pain worse on inspiration – 50%
Cough, hemoptysis
Possibly decreased breath sounds, dullness on percussion, split s2
Tachycardia, hypotension (25%)
Jugular venous distension, kussmaul sign – in massive PE
Low grade fever
Features of DVT:
o Unilateral painful leg swelling
In extreme cases syncope, obstructive shock with circulatory collapse e.g. due to saddle
thrombus.
Pre-test probability of pulmonary embolism + scoring systems
A number of scoring systems can be used to asses risk and probability of PE:
o Wells Score
o Revised Geneva Score Original wells score:
o Pulmonary Embolism Rule out Criteria (PERC) 0-1 point = low risk (6%) 2-6
points – moderate risk (23%)
Wells Criteria for PE >7 points – high risk (49%)
Modified wells score :
Clinical DVT symptoms = 3 points Score <4 – PE is unlikely (8%)
PE more likely than other diagnosis = 3 points Total score >4 PE is likely (34%)
Previous PE/DVT = 1.5 points
Tachycardia = 1.5 points
Surgery or immbolization in last 4 weeks = 1.5 points
Hemoptysis = 1 point
Malignancy = 1 point
PERC – used for patients with a low pretest probability of PE based on their wells score:
age >50 = 1 point
heart rate >100 = 1 point
oxygen saturation <95% = 1 point
hemoptysis = 1 point
estrogen use = 1 point
prior history of DVT/PE = 1 point
recent surgery or trauma = 1 point
unilateral lower limb edema = 1 point
any score of 1 or more means that PE cannot be ruled out and further tests should be done to rule it out.
Diagnosis:
D-dimer levels – any level >500ng/ml requires further testing
Arterial blood gasses, CBC, troponin (may be increased) BNP or NT-proBNP may also be high
CT pulmonary angiography – CTPA
o Contrast enhanced imaging of the pulmonary arteries
o Most definitive diagnostic test for pulmonary embolism
o Shows visible intraluminal filling defects of pulmonary arteries
o Wedge shape infarction with pleural effusion is pathognomic for PE
V/Q scan – ventilation perfusion scintigraphy
o Shows areas of ventilation perfusion mismatch via perfusion and ventilation scintigraphy
o Shows an area of VQ mismatch
Echocardiography
1. Pulmonary embolism
Definitions:
Pulmonary Embolism (PE) – obstruction of the lumen of one or more pulmonary arteries. Most
often due to blood thrombi from deep vein thrombosis DVT that dislodge and become emboli.
Venous Thromboembolism (VTE) – umbrella term that includes PE + DVT
o Recurrent VTE – VTE that recurs in a patient after completing 2 weeks of antithrombotic
therapy.
o Provoked VTE – VTE in a person with one or more risk factors for VTE
o Unprovoked (idiopathic) VTE – in an individual without any risk factors.
Epidemio:
Increasing incidence with age
Overall more common in males, but females have a slight increase during reproductive years.
Etiology:
DVT is the most common cause
Other causes – fat embolism (after major surgery)
Air embolism, amniotic fluid embolism, tumor emboli
Risk Factors:
o Pregnancy
o Major surgeries
o Varicose veins
o Oral contraceptives
o Bed rest or inactivity
o Heart disease or prior DVT
Pathophysio:
Thrombus formation DVT in the legs or pelvis, most common is the iliac vein embolization to
pulmonary arteries via the inferior vena cava partial or complete obstruction of pulmonary
arteries.
Response of the lung to arterial obstruction:
o Pleuritic pain + hemoptysis
o Surfactant dysfunction atelectasis decreased oxygen sat
o Triggers resp drive hyperventilation, tachypnea resp alkalosis with hypocapnia
o Impaired gas exchange arterial hypoxemia
o Cardiac compromise
Increased pulmonary artery pressure (PAP) due to blockage right ventricular
pressure overload forward failure with decreased cardiac output hypotension
and tachycardia.
o Pulmonary vasoconstriction – via thromboxane A2, prostaglandins, adenosine, thrombin and
serotonin secreted by activated platelets and the thrombus pulmonary vasoconstriction
and bronchospasm.
, Clinical Features:
Acute onset of symptoms, triggered by specific event usually standing up in the morning, physical
exercise
Dyspnea, Tachypnea - >50%
Sudden pleuritic chest pain worse on inspiration – 50%
Cough, hemoptysis
Possibly decreased breath sounds, dullness on percussion, split s2
Tachycardia, hypotension (25%)
Jugular venous distension, kussmaul sign – in massive PE
Low grade fever
Features of DVT:
o Unilateral painful leg swelling
In extreme cases syncope, obstructive shock with circulatory collapse e.g. due to saddle
thrombus.
Pre-test probability of pulmonary embolism + scoring systems
A number of scoring systems can be used to asses risk and probability of PE:
o Wells Score
o Revised Geneva Score Original wells score:
o Pulmonary Embolism Rule out Criteria (PERC) 0-1 point = low risk (6%) 2-6
points – moderate risk (23%)
Wells Criteria for PE >7 points – high risk (49%)
Modified wells score :
Clinical DVT symptoms = 3 points Score <4 – PE is unlikely (8%)
PE more likely than other diagnosis = 3 points Total score >4 PE is likely (34%)
Previous PE/DVT = 1.5 points
Tachycardia = 1.5 points
Surgery or immbolization in last 4 weeks = 1.5 points
Hemoptysis = 1 point
Malignancy = 1 point
PERC – used for patients with a low pretest probability of PE based on their wells score:
age >50 = 1 point
heart rate >100 = 1 point
oxygen saturation <95% = 1 point
hemoptysis = 1 point
estrogen use = 1 point
prior history of DVT/PE = 1 point
recent surgery or trauma = 1 point
unilateral lower limb edema = 1 point
any score of 1 or more means that PE cannot be ruled out and further tests should be done to rule it out.
Diagnosis:
D-dimer levels – any level >500ng/ml requires further testing
Arterial blood gasses, CBC, troponin (may be increased) BNP or NT-proBNP may also be high
CT pulmonary angiography – CTPA
o Contrast enhanced imaging of the pulmonary arteries
o Most definitive diagnostic test for pulmonary embolism
o Shows visible intraluminal filling defects of pulmonary arteries
o Wedge shape infarction with pleural effusion is pathognomic for PE
V/Q scan – ventilation perfusion scintigraphy
o Shows areas of ventilation perfusion mismatch via perfusion and ventilation scintigraphy
o Shows an area of VQ mismatch
Echocardiography
