Block A - Medicine - Respiratory Data Interpretation

Question 1

Case scenario

• Chronic smoker for 40 pack years
• With progressive exertional dyspnea for 5 years
• Chronic cough with white sputum for 10 years
• Reduced exercise tolerance from 3 FOS to 1 FOS for 1 year
• Purulent sputum and dyspnea at rest for 3 days

Ddx

Answer 1

Chronic lung pathologies:

• COPD
• Bronchiectasis

Acute symptoms:

• Pneumonia
• Acute exacerbation of COPD: Pneumothorax, consolidation, pulmonary embolism

Question 2

Interpret this CXR

Most prominent features and likely dx

Answer 2

Hyperinflated lung

Slender cardiac shadow (compressed by hyperinflated lungs), low cardiothoracic ratio

Enlarged pulmonary hilum - pulmonary hypertension and pulmonary artery dilatation, cor pulmonale

Flattening of hemidiaphragm

Ddx:
Most likely COPD
chronic hypoxemia, chronic obstructive pulmonary disease and pulmonary arterial hypertension, cor pulmonale

Question 3

Interpret the following

Next step in Ix and Tx?

Answer 3

pO2 can be compensated: High pO2 can be due to oxygen supplement

pCO2 cannot be compensated: Obstructive pathology inhibits effective removal of CO2 from lung

Bicarbonate level should be much higher via renal compensation, but HCO2 level is still normal here:

• Insufficient time for renal compensation
• Impaired renal function possible

Interpretation: Acute respiratory failure and Respiratory acidosis without renal compensation

Further treatment:
Lack of renal compensation indicates assisted ventilation to remove CO2 and correct acid-base balance

Question 4

Case scenario

Chronic smoker 
SoB 3 days + fever 4 days with chills 
Cough, runny nose, sore throat 
Myalgia 
Purulent sputum, progressively worsening 

Ddx

Answer 4

Interpretation:

Upper:
 Flu-like illness (fever, chills, rigor, myalgia), runny nose, sore throat
 Viral until proven otherwise (so self-limiting)

Lower:
 Bacterial (pneumonia)
 In keeping with progressive shortness of breath

Question 5

Interpret this CXR- most prominent feature and ddx

P/E: tachypneic, localized crackles, bronchial breath sounds, increased vocal resonance

Answer 5

No cardiomegaly

Increased radiodensities in the right lung – consolidation likely in right middle lobe (below the visible horizontal fissure)

Question 6

How to distinguish right middle vs right lower lobe consolidation

Answer 6

Silhouette sign:
 If right middle lobe (right next to heart, anteriorly situated): loses normal contrast and cannot see heart border clearly
 If in lower lobe, right heart border should still be seen clearly because the middle lobe is still air- filled to contrast with the heart border

Question 7

Interpret the following

Next investigations?

Answer 7

Complete blood picture:
o Neutrophilia: bacterial infection (e.g. Streptococcus pneumoniae, Haemophilus influenzae)
o If no neutrophilia: atypical pneumonia

Ascertain causative agent of pneumonia:
viral antigen detection by immunofluorescence/ RT-PCR of the nasopharyngeal aspirate
Urinary legionella antigen test
Serology for atypical pneumonia: Mycoplasma, chlamydia

Question 8

Case scenario:

67 years old woman 
o Never-smoker with good past health
o Cough with purulent sputum for 1 week
o Presented with high fever and shortness of breath for 5 days
o Right pleuritic chest pain for 4 days

Ddx

Answer 8

Pneumonia with pleural effusion, empyema

Question 9

Interpret this CXR

Most likely Dx and next investigation for diagnosis

Answer 9

Chest X-ray: pleural effusion on the right side (increased density), in line with meniscus

Investigations:
Pleural fluid analysis: turbidity (empyema), Cell count and WBC differential count, Fluid protein, LDH, pH
Pleural fluid gram stain

Diagnosis:
1. Pleural effusion with macroscopic presence of pus;
2. A positive Gram stain or culture of pleural fluid; or
3. A pleural fluid pH <7.2 with normal peripheral blood pH (low pH in pleural fluid suggests
high level of cellular turnover, in keeping with bacterial invasion)

Question 10

Criteria for pleural effusion

Answer 10

Light’s criteria: exudate = 1 of the 3 criteria:

1. Pleural fluid total protein:serum total protein >0.5
2. Pleural fluid LDH:serum LDH >0.6
3. Pleural fluid LDH > 2/3 of the upper normal limit of serum LDH

Question 11

Case scenario:

63-year-old construction site worker
Chronic smoker, 80 pack years
cough and blood-stained sputum production for the past 3 weeks
Exertional dyspnea for the last few years, constant
Subjective weight loss over past one month

Answer 11

DDx of hemoptysis: tuberculosis, malignancy, bronchiectasis

Question 12

Interpret this CXR

Most prominent feature and likely diagnosis

Answer 12

Patch on right lung field: right upper lobe (anterior to oblique fissure)

Ddx: Consolidation, tumor

Question 13

Electrolyte disturbances a/w lung cancer

Answer 13

Hyponatremia:
 Investigate serum osmolality (decreased) with paired spot urine sodium before sodium replacement:
 SIADH: paraneoplastic syndrome of lung cancer (>20 mmol/L, euvolemic)
 Depletional (>20 mmol/L, hypovolemic)
 Water overload (<20 mmol/L, euvolemic)

Hypercalcemia:
 Bone metastasis: increased phosphate level
 PTH-like peptide (paraneoplastic syndrome of lung cancer): decreased phosphate level

Question 14

Lung cancer with metastasis

Next investigations

Answer 14

PET-CT for distant metastasis

FNAC with US guidance for LN

Bone scintigraphy scan for bony metastasis

Thoracic CT

Bronchoscopy with BAL and endobronchial biopsy