Pulmonary embolism nursing reference: assessment, interventions, and NCLEX review

Pulmonary embolism (PE) is a blockage in one or more pulmonary arteries, most commonly caused by a blood clot that travels from the deep veins of the legs or pelvis. PE is a medical emergency and a leading cause of preventable in-hospital death, responsible for an estimated 100,000–180,000 deaths annually in the United States. For nursing students, PE is high-yield: it appears across med-surg, critical care, and postoperative rotations, and it demands rapid recognition, immediate intervention, and precise pharmacological management.

This reference covers pathophysiology, the DVT-to-PE progression, Wells clinical decision rule scoring, clinical presentation, diagnostic approach, nursing interventions, anticoagulation drugs with reversal agents, patient education, and six NCLEX-style practice questions with rationales. Pair this with the ABG interpretation cheat sheet for the respiratory alkalosis and hypoxemia patterns seen in PE, and the sepsis nursing reference for the hemodynamic instability differential.

Pathophysiology

PE sits within the broader spectrum of venous thromboembolism (VTE), which encompasses both deep vein thrombosis (DVT) and pulmonary embolism. The two conditions share the same underlying pathological mechanism and are best understood together.

Virchow’s triad

Thrombus formation in the venous system follows the pattern described by Rudolf Virchow in 1856, which remains the foundational model of VTE pathophysiology. Three overlapping factors drive clot formation:

1. Venous stasis — slowed blood flow allows platelets and clotting factors to accumulate. This occurs with prolonged immobility (bedrest, long-haul flights, casting), right-sided heart failure, and obesity.
2. Hypercoagulability — an increased tendency toward clotting, driven by malignancy, pregnancy, oral contraceptive use, inherited thrombophilias (Factor V Leiden, prothrombin G20210A mutation, protein C/S deficiency), or postoperative states.
3. Endothelial injury — damage to the vessel wall from trauma, surgery, IV catheter placement, or inflammatory conditions exposes subendothelial collagen and activates the clotting cascade.

DVT progression to PE

Deep vein thrombi most often originate in the deep veins of the calf. Proximal extension into the popliteal, femoral, or iliac veins significantly increases embolic risk. When a thrombus or fragment breaks free, it travels through the right heart and lodges in the pulmonary vasculature.

The downstream effects depend on clot burden and the patient’s cardiopulmonary reserve:

• Impaired gas exchange: The embolus creates dead space — lung units that are ventilated but not perfused. This ventilation-perfusion (V/Q) mismatch causes hypoxemia. Hypoxemia drives hyperventilation, producing hypocapnia and respiratory alkalosis — the classic ABG pattern in PE.
• Increased pulmonary vascular resistance: Mechanical obstruction plus hypoxic vasoconstriction raise pulmonary arterial pressures. The right ventricle (RV) must work harder against this increased afterload.
• Right ventricular strain and failure: In massive PE, the RV dilates acutely. Elevated RV pressures cause interventricular septal shift (the septum bows leftward), reducing left ventricular filling and cardiac output. This produces hypotension, shock, and cardiovascular collapse if untreated.
• Reflex bronchoconstriction: Loss of local CO2 causes airway constriction in affected lung segments, worsening V/Q mismatch.

Risk factors and Wells score

Understanding risk factors helps nurses apply the Wells clinical decision rule, recognize high-risk patients before symptoms develop, and prioritize VTE prophylaxis.

Common VTE risk factors

Patient characteristics: Age > 60, obesity (BMI > 30), prior DVT or PE, inherited thrombophilia, malignancy (especially adenocarcinoma, hematological cancers), pregnancy or postpartum state, immobility, paralysis, long-distance travel (> 4 hours).

Procedural and situational: Major surgery (especially orthopedic — hip/knee replacement, hip fracture repair), central venous catheter, trauma, hospitalization, acute medical illness with bedrest.

Hormonal: Oral contraceptives (estrogen-containing), hormone replacement therapy, selective estrogen receptor modulators (tamoxifen, raloxifene).

Wells clinical decision rule for PE

The Wells score is the most widely used pre-test probability tool for PE. It stratifies patients into low, moderate, or high risk, which determines whether imaging is required or whether D-dimer testing alone is sufficient to rule out PE. Nursing students are expected to know the Wells criteria and understand how the score drives diagnostic decision-making.

PERC rule: In patients with Wells score < 2 and a clinical gestalt suggesting low PE probability (< 15%), the PERC rule can rule out PE without D-dimer testing if all 8 criteria are negative: age < 50, heart rate < 100, SpO2 ≥ 95%, no hemoptysis, no estrogen use, no prior DVT/PE, no unilateral leg swelling, no recent surgery or trauma requiring hospitalization within 4 weeks.

Clinical presentation

PE is often called “the great masquerader” because its presentation ranges from mild dyspnea to sudden cardiac arrest. This variability makes systematic assessment critical.

Symptoms and signs by severity

Low-risk (non-massive) PE — The patient is hemodynamically stable. Symptoms are often subacute and may be mistaken for anxiety, musculoskeletal chest pain, or an exacerbation of underlying lung disease.

• Dyspnea (sudden onset, at rest or with minimal exertion — present in ~80% of cases)
• Pleuritic chest pain (sharp, worsens with inspiration — suggests infarction of peripheral lung tissue)
• Hemoptysis (blood-streaked sputum — indicates pulmonary infarction; present in only 10–30%)
• Tachycardia (most common objective finding)
• Low-grade fever (from the inflammatory response to infarction)
• Anxiety, restlessness, sense of impending doom

Submassive PE — Right ventricular dysfunction or myocardial necrosis (elevated troponin and/or BNP) without systemic hypotension. The patient may appear relatively stable but has an elevated short-term mortality risk.

Massive PE — Life-threatening hemodynamic collapse:

• Systemic hypotension (systolic BP < 90 mmHg or sustained drop ≥ 40 mmHg from baseline)
• Cardiogenic shock: cold/clammy extremities, altered mental status, oliguria
• Syncope or near-syncope
• Signs of right heart strain: elevated jugular venous pressure (JVP), S3 gallop, new right bundle branch block on ECG
• Pulseless electrical activity (PEA) cardiac arrest in extreme cases

Atypical presentations

Elderly patients may present with altered mental status or syncope as the primary complaint, with minimal respiratory symptoms. Patients with significant cardiopulmonary reserve (e.g., young, otherwise healthy adults) can appear deceptively stable with a large clot burden. Conversely, patients with pre-existing COPD or heart failure may decompensate rapidly with even a small PE. See the head-to-toe assessment reference for a systematic approach to identifying subtle changes on admission assessment.

Diagnosis

D-dimer

D-dimer is a fibrin degradation product released when a clot is broken down. It is highly sensitive for VTE (≥ 95%) but not specific — D-dimer is elevated in many conditions including infection, malignancy, pregnancy, post-surgery, and trauma. A negative D-dimer effectively rules out PE in low-to-moderate pre-test probability patients. A positive D-dimer requires imaging to confirm or exclude PE.

The nursing lab values cheat sheet includes D-dimer reference ranges. Note that many labs now use age-adjusted D-dimer cutoffs (patient age × 10 mcg/L in patients > 50 years) to reduce false positives in older adults.

CT pulmonary angiography (CTPA)

CTPA is the gold-standard imaging study for PE. It directly visualizes the pulmonary vasculature and can identify emboli down to the segmental and sub-segmental level. Sensitivity is 83–94%, specificity is 96%. CTPA is contraindicated in severe renal impairment (contrast nephropathy risk) and contrast allergy; in these cases, V/Q scan is the alternative.

Ventilation-perfusion (V/Q) scan

V/Q scanning is the alternative when CTPA is contraindicated or unavailable. Results are reported as normal, low probability, intermediate probability, or high probability. A high-probability V/Q scan with high clinical pre-test probability confirms PE. A normal V/Q scan excludes PE.

ECG findings

ECG is abnormal in up to 70% of PE cases but changes are non-specific. Key patterns to recognize:

• Sinus tachycardia — most common finding; present in up to 44% of PE cases
• S1Q3T3 pattern — S wave in lead I, Q wave in lead III, T-wave inversion in lead III — a sign of acute right heart strain; present in only ~20% of PEs but high-yield for NCLEX
• Right bundle branch block (RBBB) — new RBBB suggests right heart strain from elevated pulmonary pressures
• Right axis deviation
• T-wave inversions in V1–V4 — reflecting right ventricular strain

ABG findings

The classic ABG in PE shows: hypoxemia (PaO2 < 80 mmHg), hypocapnia (PaCO2 < 35 mmHg), and respiratory alkalosis (pH > 7.45). This pattern reflects V/Q mismatch driving hyperventilation as the patient attempts to compensate for hypoxemia. See the ABG interpretation cheat sheet for the full analysis framework.

Additional labs

• Troponin I or T: Elevated in submassive/massive PE (right ventricular myocardial injury); associated with higher short-term mortality
• BNP/NT-proBNP: Elevated with right ventricular strain; used for risk stratification
• CBC: Assess baseline hemoglobin (affects anticoagulation decisions); rule out thrombocytopenia before anticoagulation
• Coagulation panel (PT/INR, aPTT): Baseline before initiating anticoagulation; aPTT used to monitor UFH therapy

Nursing interventions

Immediate priorities: airway, breathing, circulation

1. Airway and oxygenation: Apply supplemental oxygen to maintain SpO2 > 94%. Start at 2–4 L/min via nasal cannula for mild hypoxemia; escalate to non-rebreather mask or high-flow nasal cannula for severe hypoxemia. Prepare for potential intubation in massive PE with respiratory failure.
2. Position: Head of bed elevated 30–45° (semi-Fowler’s) to optimize diaphragmatic excursion and lung expansion. Avoid the Trendelenburg position — it increases right ventricular preload and worsens RV strain in massive PE.
3. IV access: Establish large-bore peripheral IV access (16–18 gauge) for rapid medication administration. Two peripheral IVs preferred; central access if vasopressors are anticipated.
4. Hemodynamic monitoring: Continuous cardiac monitoring (pulse oximetry, cardiac telemetry). Obtain baseline vital signs including bilateral blood pressures. Anticipate frequent reassessment — every 15–30 minutes in the acute phase.
5. Emergency preparation: Keep crash cart accessible. Massive PE with PEA arrest requires CPR; thrombolysis has the highest success rate when given during active resuscitation.

Anticoagulation administration

Anticoagulation is the cornerstone of PE treatment. It does not dissolve existing clots — it prevents clot propagation and new thrombus formation, allowing the fibrinolytic system to resolve the embolus over days to weeks.

• Unfractionated heparin (UFH): IV bolus followed by continuous infusion, titrated by weight-based or aPTT-guided protocol. Monitor aPTT every 6 hours until therapeutic (1.5–2.5× baseline), then every 24 hours. Monitor for heparin-induced thrombocytopenia (HIT) — check platelet count every 2–3 days.
• Low-molecular-weight heparin (LMWH / enoxaparin): Subcutaneous injection, weight-based dosing. Preferred over UFH for most hemodynamically stable patients due to predictable pharmacokinetics. Monitor anti-Xa levels in renal impairment or obesity. Avoid in severe renal failure (CrCl < 30 mL/min).
• Direct oral anticoagulants (DOACs): Rivaroxaban or apixaban can be started without parenteral bridging for acute PE in hemodynamically stable patients. Fixed dosing, no routine lab monitoring required.

Thrombolytic therapy (massive PE)

Systemic thrombolysis with alteplase (tPA) is reserved for massive PE with hemodynamic instability. Alteplase 100 mg IV over 2 hours dissolves the clot directly. Major contraindications include recent surgery (within 10 days), active bleeding, prior hemorrhagic stroke, or head trauma. Monitor for bleeding at all puncture sites, neurological changes, and signs of intracranial hemorrhage.

IVC filter

An inferior vena cava (IVC) filter is a mesh device placed percutaneously to trap emboli before they reach the lungs. Indications: contraindication to anticoagulation (active bleeding, recent surgery) combined with confirmed DVT/PE. Retrievable filters are preferred when anticoagulation is temporarily contraindicated.

Ongoing monitoring and safety

• Bleeding precautions: All anticoagulated patients require fall risk assessment, soft toothbrush, electric razor, no IM injections. Monitor for signs of occult bleeding: guaiac-positive stool, gross hematuria, sudden drop in hemoglobin, unexplained tachycardia or hypotension.
• DVT assessment: Inspect lower extremities every shift for asymmetric swelling, erythema, warmth, or pain (Homan’s sign is unreliable and no longer recommended for clinical assessment).
• Pain management: Pleuritic chest pain responds to positioning and analgesics. Non-opioid analgesics preferred when possible to avoid respiratory depression.

Anticoagulation reference table

Patient education

Patients diagnosed with PE require clear, structured education before discharge, as anticoagulation adherence and recurrence prevention depend on patient understanding.

Anticoagulation duration: Most patients with PE require anticoagulation for a minimum of 3 months. Patients with an unprovoked PE (no identifiable reversible risk factor), malignancy-associated PE, or recurrent VTE typically require indefinite anticoagulation. Stopping anticoagulation early significantly increases recurrence risk.

Signs of bleeding to report immediately: Unusual bruising, prolonged bleeding from cuts, red/pink/dark urine, red or tarry stools, coughing or vomiting blood, severe headache, sudden vision changes, or weakness/numbness in the face or extremities. Patients on warfarin should understand that any significant change in diet, new medication (including OTC drugs and supplements), or illness can affect INR.

VTE prevention behaviors: Ambulate as soon as medically cleared — even short walks every 1–2 hours break venous stasis. Stay well hydrated. Avoid prolonged sitting with legs crossed or hanging. Wear compression stockings as prescribed. During long-haul travel, walk every 1–2 hours, perform ankle pumping exercises, and stay hydrated. Avoid tight-fitting clothing around the waist or legs.

When to seek emergency care: Return to the ED immediately for sudden worsening shortness of breath, chest pain, coughing up blood, leg swelling with pain, syncope, or signs of bleeding listed above. Patients should carry a medication card identifying their anticoagulant and dose.

NCLEX-style practice questions

1. A nurse is caring for a postoperative patient on day 2 following total hip replacement. The patient suddenly reports shortness of breath and sharp chest pain that worsens with breathing. Oxygen saturation drops from 98% to 90%. Which action should the nurse take first?

A. Administer prescribed PRN analgesic for the chest pain B. Notify the provider and prepare for diagnostic imaging C. Apply supplemental oxygen and elevate the head of bed D. Obtain an ECG to evaluate for myocardial infarction

Correct answer: C. The priority action follows the ABCs — airway and breathing come first. Supplemental O2 and HOB elevation address the immediate hypoxemia and respiratory compromise. Notifying the provider and preparing for imaging (B) is the correct second action, but oxygenation takes precedence. An ECG (D) may be obtained but is secondary to stabilizing the patient.

2. A nurse is reviewing the laboratory results for a patient being evaluated for possible PE. The D-dimer result is elevated. Which statement best explains the clinical significance of this finding?

A. An elevated D-dimer confirms that the patient has a pulmonary embolism B. An elevated D-dimer indicates that systemic thrombolysis is needed C. An elevated D-dimer is sensitive but not specific — it indicates further imaging is required D. An elevated D-dimer rules out the need for anticoagulation

Correct answer: C. D-dimer is highly sensitive (detects most cases of VTE) but not specific (elevated in many conditions including infection, malignancy, recent surgery, and pregnancy). An elevated result does not confirm PE; it indicates that imaging — typically CTPA — is needed. A negative D-dimer in a low-to-moderate probability patient effectively rules out PE.

3. A nurse is administering IV unfractionated heparin to a patient with confirmed PE. The patient’s aPTT result is 45 seconds (baseline 28 seconds). How should the nurse interpret this result and what action is appropriate?

A. The aPTT is supratherapeutic — hold the heparin infusion and notify the provider B. The aPTT is subtherapeutic — follow the heparin protocol to increase the infusion rate C. The aPTT is therapeutic — continue the current infusion rate D. The aPTT is irrelevant — heparin dose is weight-based and does not require monitoring

Correct answer: B. The therapeutic aPTT range for heparin anticoagulation is 60–100 seconds, or 1.5–2.5 times baseline. At 45 seconds (1.6× baseline of 28), this patient is subtherapeutic, meaning the heparin dose is insufficient to prevent clot propagation. The nurse should follow the institutional weight-based heparin protocol to increase the infusion rate and notify the provider. Supratherapeutic aPTT (> 100 seconds) would require holding or reducing the infusion.

4. A patient with massive PE is being evaluated for systemic thrombolysis with alteplase. Which finding in the patient’s history is a contraindication to thrombolytic therapy?

A. Age > 75 years B. Known malignancy C. Ischemic stroke 3 weeks ago D. Current use of enoxaparin

Correct answer: C. A recent ischemic stroke within the prior 3 months is a major contraindication to systemic thrombolysis due to the risk of hemorrhagic transformation. Other major contraindications include recent intracranial surgery or head trauma, active internal bleeding, and recent major surgery within 10 days. Age > 75 (A) increases bleeding risk and warrants careful risk-benefit analysis, but is not an absolute contraindication. Malignancy (B) is not a contraindication. Transitioning from enoxaparin (D) to thrombolysis requires discontinuation but is not a contraindication.

5. A nurse is caring for a patient receiving anticoagulation therapy for PE. Which assessment finding requires the nurse to notify the provider immediately?

A. aPTT of 75 seconds on UFH infusion B. INR of 2.5 on warfarin therapy C. Platelet count of 58,000/mm³ on day 6 of heparin therapy D. Mild bruising at enoxaparin injection sites

Correct answer: C. A platelet count of 58,000/mm³ after 6 days of heparin therapy raises strong concern for heparin-induced thrombocytopenia (HIT), a life-threatening immune-mediated complication. HIT typically presents on days 4–14 of heparin exposure with a platelet drop of ≥ 50% from baseline. The nurse must notify the provider immediately — heparin should be discontinued and a non-heparin anticoagulant (argatroban, fondaparinux, bivalirudin) initiated. aPTT 75 seconds (A) and INR 2.5 (B) are therapeutic. Injection site bruising (D) is expected with subcutaneous anticoagulants.

6. A nursing student is preparing to discharge a patient following treatment for DVT and PE. Which statement by the patient indicates that teaching has been effective?

A. “I should stop my blood thinner as soon as I feel back to normal” B. “I will eat more leafy green vegetables to help my blood clot normally while on warfarin” C. “I should walk short distances every one to two hours during my flight home next week” D. “Compression stockings are only needed if my legs start swelling again”

Correct answer: C. Regular ambulation during prolonged travel — walking every 1–2 hours — is the single most effective behavioral strategy for preventing recurrent DVT in the short term. It breaks venous stasis, the first component of Virchow’s triad. Stopping anticoagulation early (A) is incorrect — a minimum of 3 months is required. Increasing leafy greens (B) is incorrect for warfarin patients, as vitamin K antagonizes warfarin’s effect and destabilizes INR. Compression stockings (D) should be worn consistently for prophylaxis, not only in response to symptoms.