Section 2.4: Restrictive, Vascular & Neoplastic Pulmonary Conditions

Restrictive, Vascular & Neoplastic Pulmonary Conditions (PE, Pneumothorax, Sleep Apnea)

Why This Topic Matters for the PANCE

Vascular, pleural, and sleep-related pulmonary conditions represent major emergency medicine and primary care topics on the PANCE. Candidates must be proficient in risk-stratifying suspected pulmonary embolism (PE) using the Wells criteria, understanding when to use D-dimer versus CT pulmonary angiography (CTPA), and executing acute stabilization protocols. Additionally, you must be able to immediately recognize tension pneumothorax clinically and distinguish it from spontaneous pneumothorax, and understand the pathophysiology, diagnostic sleep study criteria, and cardiovascular consequences of obstructive sleep apnea (OSA).

Pulmonary Embolism (PE)

Pathophysiology

A pulmonary embolism occurs when a thrombus (or other material, such as fat, air, or amniotic fluid) embolizes to the pulmonary arterial bed, obstructing blood flow. Over 90% of PEs originate from a deep vein thrombosis (DVT) in the lower extremities (specifically the proximal veins: popliteal, femoral, or iliac). The formation of thrombi is driven by Virchow's Triad: venous stasis, endothelial injury, and hypercoagulability.

• V/Q Mismatch: Occlusion of the pulmonary artery stops perfusion to ventilated alveoli, creating alveolar dead space (ventilation without perfusion).
• Right Heart Strain: The sudden obstruction increases pulmonary vascular resistance, forcing the right ventricle (RV) to pump against a higher afterload. This leads to acute RV dilation, bowing of the interventricular septum, decreased left ventricular filling, reduced cardiac output, and potentially obstructive shock.

Diagnostic Workup and Wells Criteria

Initial assessment begins with calculating the Wells Criteria for PE to estimate pretest probability:

• Clinical Signs of DVT (3 points)

• Alternative Diagnosis Less Likely than PE (3 points)

• Heart Rate > 100 bpm (1.5 points)

• Immobilization >= 3 days or Surgery in past 4 weeks (1.5 points)

• Previous DVT or PE (1.5 points)

• Hemoptysis (1 point)

• Malignancy with active treatment in past 6 months (1 point)

• Triage Algorithm:

  • Wells Score <= 4 (PE Unlikely): Perform a high-sensitivity D-dimer test. A normal D-dimer (< 500 ng/mL or age-adjusted threshold) has a high negative predictive value and safely rules out PE. If elevated, proceed to CTPA.
  • Wells Score > 4 (PE Likely): Proceed directly to CT Pulmonary Angiography (CTPA), which is the gold standard diagnostic test of choice.
  • Alternative: A Ventilation-Perfusion (V/Q) scan is indicated if CTPA is contraindicated (e.g., severe renal insufficiency, contrast allergy, or pregnancy).

• ECG Findings: Sinus tachycardia is the most common finding. Look for signs of right heart strain, including T-wave inversions in V1-V4, and the classic but rare S1Q3T3 pattern (deep S-wave in lead I, Q-wave in lead III, and inverted T-wave in lead III).

Clinical Management

• Hemodynamically Stable: Anticoagulation is first-line. Initiate immediately with Low-Molecular-Weight Heparin (LMWH, e.g., enoxaparin) or direct oral anticoagulants (DOACs, e.g., apixaban or rivaroxaban) for a minimum of 3 months.
• Hemodynamically Unstable (Systolic BP < 90 mmHg): Thrombolytic therapy (systemic Alteplase) is indicated. If contraindicated, perform catheter-directed or surgical embolectomy.
• Inferior Vena Cava (IVC) Filter: Indicated only in patients with documented acute DVT/PE who have an absolute contraindication to anticoagulation or recurrent PE despite therapeutic anticoagulation.

Pneumothorax

A pneumothorax is the presence of air in the pleural space, which disrupts the negative pressure holding the lung open, causing collapse.

• Primary Spontaneous Pneumothorax: Occurs without underlying lung disease or trauma, typically in tall, thin young males (aged 10-30 years) due to the rupture of subpleural apical blebs.
• Secondary Spontaneous Pneumothorax: Occurs in patients with pre-existing lung disease (most commonly COPD, but also cystic fibrosis, tuberculosis, or PCP pneumonia).
• Tension Pneumothorax: A life-threatening emergency. A laceration in the lung parenchyma or chest wall acts as a one-way valve, allowing air to enter the pleural space during inspiration but trapping it during expiration. This leads to progressive air accumulation, compressing the ipsilateral lung and shifting the mediastinum to the contralateral side. The mediastinal shift compresses the superior and inferior vena cava, preventing venous return to the heart and causing obstructive shock.

Clinical Presentation and Diagnosis

• Spontaneous Pneumothorax: Presents with sudden-onset unilateral pleuritic chest pain and dyspnea. Physical exam reveals decreased or absent breath sounds, hyperresonance to percussion, and decreased tactile fremitus on the affected side. Upright expiratory chest X-ray confirms the diagnosis by showing a visceral pleural line with no peripheral lung markings.
• Tension Pneumothorax: Presents with severe respiratory distress, marked hypotension, tachycardia, jugular venous distention (JVD), and tracheal deviation away from the affected side. This is a clinical diagnosis. Do NOT wait for a chest X-ray to confirm if the patient is hemodynamically unstable.

Management

• Small (< 20% hemithorax), Stable Spontaneous: Observation and high-flow supplemental oxygen (enhances pleural nitrogen absorption). Repeat chest X-ray in 6 hours.
• Large (> 20%) or Symptomatic Spontaneous: Needle aspiration or small-bore chest tube (pigtail catheter).
• Secondary Spontaneous: Chest tube thoracostomy, regardless of size, due to poor pulmonary reserve.
• Tension Pneumothorax: Immediate needle decompression using a large-bore angiocatheter (14-16 gauge) in the second intercostal space at the midclavicular line (or 4th/5th intercostal space at the anterior axillary line). Follow immediately with chest tube thoracostomy.

Obstructive Sleep Apnea (OSA)

OSA is characterized by repetitive collapse and obstruction of the upper airway during sleep, resulting in nocturnal hypoxemia, sleep fragmentation, and sympathetic surges. The primary site of obstruction is the oropharynx.

• Risk Factors: Obesity (BMI > 30 kg/m²), male sex, collar size > 17 inches in men (> 16 inches in women), micrognathia, retrognathia, and tonsillar hypertrophy.
• Clinical Presentation: Loud, irregular snoring, witnessed apneas, gasping or choking episodes, daytime somnolence, morning headaches (due to hypercapnia), and cognitive impairment. On exam, patients often have a crowded posterior pharynx (Mallampati class III or IV).
• Diagnostic Workup: In-lab Polysomnography (sleep study) is the gold standard. A diagnosis is established if the Apnea-Hypopnea Index (AHI) is >= 5 events per hour with symptoms, or >= 15 events per hour regardless of symptoms.
• Clinical Management:
  • First-line: Continuous Positive Airway Pressure (CPAP). It acts as a pneumatic splint to keep the airway open.
  • Behavioral: Weight loss, avoidance of alcohol and sedatives, and side-sleeping (positional therapy).
  • Alternative: Custom oral appliances (mandibular advancement devices) for mild-to-moderate OSA.
• Cardiovascular Consequences: Untreated OSA is a major cause of resistant systemic hypertension, pulmonary hypertension, coronary artery disease, atrial fibrillation, and stroke.

Classic PANCE Traps and Clinical Pearls

• Tension Pneumothorax Triage: Never delay treatment to obtain an imaging study if tension pneumothorax is suspected in an unstable patient. Perform immediate needle decompression.
• ECG Classic vs. Common: The S1Q3T3 pattern is a classic board question clue for PE, but it is highly insensitive. The most common ECG finding in a pulmonary embolism is sinus tachycardia.
• Secondary Pneumothorax: While a small primary spontaneous pneumothorax can be managed with observation, a secondary spontaneous pneumothorax (e.g., in a COPD patient) requires a chest tube due to the high risk of rapid decomposition.

Pleural Effusion

A pleural effusion is an accumulation of fluid in the pleural space. It is classified by Light's criteria into a transudate (protein < 2.5 g/dL, LDH < 200, fluid/serum LDH ratio < 0.6) or an exudate (any of the opposite criteria).

• Transudative causes: Heart failure, cirrhosis, nephrotic syndrome, hypoalbuminemia (systemic causes of increased hydrostatic or decreased oncotic pressure).
• Exudative causes: Pneumonia (parapneumonic), malignancy (lung cancer, mesothelioma, metastatic disease), tuberculosis, pulmonary embolism, connective tissue disease.
• Clinical Presentation: Dyspnea, pleuritic chest pain, decreased breath sounds, dullness to percussion, and decreased tactile fremitus on the affected side.
• Imaging: Chest X-ray shows blunting of the costophrenic angle (lateral view is more sensitive). Large effusions cause mediastinal shift away from the effusion. Ultrasound and CT are more sensitive and help guide thoracentesis.
• Management: Diagnostic thoracentesis if the cause is unclear or the effusion is large. Treat the underlying cause. Empyema (infected pleural fluid) requires chest tube drainage; parapneumonic effusions with a pH < 7.2 also require drainage.