Confusable diagnoses · PANCE / PANRE

Pulmonary Embolism vs Pneumothorax

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Pulmonary Embolism and Pneumothorax are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.

Pulmonary Embolism vs Pneumothorax at a glance

  • Pulmonary Embolism: Obstruction of pulmonary arterial circulation, usually by deep venous thrombus.
  • Pneumothorax: Air in the pleural space — spontaneous, traumatic, iatrogenic, or tension physiology.

Try two board-style questions on Pulmonary Embolism vs Pneumothorax

Real questions from the FirstPassPA bank, with the full explanation. Pick an answer — no signup, no email.

Question 1PulmonaryEasy
A 30-year-old pregnant female (12 weeks) develops acute pleuritic chest pain, dyspnea, and tachycardia. Lower extremity Doppler shows a right popliteal deep vein thrombosis (DVT). CXR is normal. Ventilation/perfusion scanning confirms a segmental pulmonary embolism. Which of the following is the most appropriate anticoagulation?
  • ADabigatran
  • BWarfarin
  • CSubcutaneous unfractionated heparin
  • DLow molecular weight heparin
Reveal answer & full explanation
Correct answer: D — Low molecular weight heparin
  • ADabigatran
  • BWarfarin
  • CSubcutaneous unfractionated heparin
  • DLow molecular weight heparin✓

Why Low molecular weight heparin is correct

  • LMWH (e.g., enoxaparin 1 mg/kg SQ BID or 1.5 mg/kg daily) is the preferred anticoagulant for pulmonary embolism in pregnancy and is favored over unfractionated heparin for outpatient management.
  • Switch to UFH near delivery because of its shorter half-life.
  • Imaging note: V/Q scan is preferred when CXR is normal (lower maternal breast radiation; fetal dose similar to CT-PA); CT-PA is preferred if CXR is abnormal. Both are acceptable per ACOG.

Why the others are wrong

  • Dabigatran — a DOAC; all DOACs are contraindicated in pregnancy due to insufficient safety data and teratogenicity concerns (wrong-drug-class).
  • Warfarin — teratogenic in the first trimester (fetal warfarin syndrome) and associated with third-trimester fetal hemorrhage (contraindicated-in-pregnancy).
  • Subcutaneous unfractionated heparin — acceptable in pregnancy but LMWH is preferred for outpatient management due to more predictable pharmacokinetics (right-class-second-choice).

Additional high-yield points

  • IVC filter is reserved for cases in which anticoagulation is absolutely contraindicated.
  • Continue anticoagulation for 6 weeks postpartum (minimum 3 months total).
Question 2PulmonaryMedium
A 32-year-old tall, thin male has sudden right-sided pleuritic chest pain and dyspnea at rest. CXR shows a 25% right pneumothorax. SpO2 97%, HR 88, BP 118/74. Which of the following is the most likely diagnosis?
  • APrimary spontaneous pneumothorax
  • BPneumothorax with tension physiology
  • CMarfan syndrome-related pneumothorax
  • DUnrecognized traumatic pneumothorax
Reveal answer & full explanation
Correct answer: A — Primary spontaneous pneumothorax
  • APrimary spontaneous pneumothorax✓
  • BPneumothorax with tension physiology
  • CMarfan syndrome-related pneumothorax
  • DUnrecognized traumatic pneumothorax

Why Primary spontaneous pneumothorax is correct

  • Primary spontaneous pneumothorax (PSP) classically occurs in tall, thin young males due to rupture of subpleural apical blebs.
  • Onset at rest with a normal blood pressure, heart rate, and oxygen saturation argues against tension physiology.
  • CXR confirming a 25% pneumothorax in a young patient with no chronic lung disease described fits the primary (not secondary) form.

Why the others are wrong

  • Pneumothorax with tension physiology — tension produces hypotension, tachycardia, hypoxia, and tracheal shift; this patient has BP 118/74, HR 88, and SpO2 97% (anchoring on pneumothorax size).
  • Marfan syndrome-related pneumothorax — a tall, thin habitus is itself the classic primary spontaneous body type, and no skeletal, ocular, or aortic root findings are described (buzzword-matching on body habitus).
  • Unrecognized traumatic pneumothorax — traumatic pneumothorax follows blunt, penetrating, or iatrogenic injury; this one began spontaneously at rest with no injury reported (premature closure).

Additional high-yield points

  • Management by size: small (<20%) and stable — high-flow O2 plus observation; large (>20%) or symptomatic — needle aspiration or chest tube; recurrent or bilateral — VATS bullectomy plus pleurodesis.
  • Activity restriction: avoid air travel and scuba diving until resolved.
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Side-by-side comparison

FeaturePulmonary EmbolismPneumothorax
At a glanceObstruction of pulmonary arterial circulation, usually by deep venous thrombus.Air in the pleural space — spontaneous, traumatic, iatrogenic, or tension physiology.
Classic presentationHampton hump (peripheral wedge-shaped opacity), Westermark sign (focal oligemia), Fleischner sign (enlarged pulmonary artery) on CXR — all insensitive.; Sudden dyspnea (most common), pleuritic chest pain, cough; Hemoptysis (rare; suggests pulmonary infarction); Syncope or near-syncope (suggests hemodynamically significant PE);…Sudden unilateral pleuritic pain + decreased breath sounds + hyperresonance in tall, thin young man = primary spontaneous pneumothorax until proven otherwise.; Sudden ipsilateral pleuritic chest pain and dyspnea; PSP often during rest or sleep; may be mild and self-limited; Severe distress in SSP (limited reserve) and tension PTX;…
Workup / key labsConfirmed PE on imaging. Use validated clinical decision rules: Wells score, three-tier (low <2, moderate 2-6, high >6) or two-tier (≤4 PE unlikely → D-dimer; >4 PE likely → CTPA directly, no D-dimer), or revised Geneva. PERC rule (8 criteria) can exclude PE in low-probability patients (<15%) without further testing.; D-dimer —…Confirmed by imaging in stable patient. Tension PTX is a CLINICAL diagnosis (hypotension, absent breath sounds, distended neck veins) requiring immediate decompression.; Most cases require no specific labs; obtain ABG/SpO2 to assess oxygenation; Consider underlying disease workup if SSP
ImagingCT pulmonary angiography (CTPA) — gold standard if no contraindication; V/Q scan — alternative if CTPA contraindicated (renal failure, contrast allergy); preferred in pregnancy when the CXR is normal (CTPA if the CXR is abnormal); Lower extremity Doppler — supportive when PE imaging contraindicated; Echocardiogram — RV…Upright PA chest radiograph — visceral pleural line with absent lung markings peripheral to it; Standard inspiratory erect film is adequate (expiratory films add no diagnostic yield); lateral decubitus view, ultrasound, or CT can detect small or occult pneumothoraces; Bedside lung ultrasound — high sensitivity (absent lung sliding, lung…
First-line treatmentAnticoagulation while awaiting imaging if high clinical suspicion and low bleeding risk; Hemodynamically stable PE: direct oral anticoagulant (DOAC) preferred — apixaban (10 mg BID × 7 d, then 5 mg BID) or rivaroxaban (15 mg BID × 21 d, then 20 mg daily) — no parenteral lead-in; Alternative: dabigatran or edoxaban (require initial…Tension pneumothorax (CLINICAL DIAGNOSIS): immediate needle decompression (14-16 gauge angiocatheter) at 4th-5th intercostal space, anterior or mid-axillary line (preferred over the historical 2nd intercostal space midclavicular line per ATLS 10th edition) — followed by definitive tube thoracostomy; Open pneumothorax (sucking chest…

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Full outlines

Pulmonary Embolism (PE) Pneumothorax (Spontaneous and Tension) All 514 diagnoses

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.