K

PNEUMOTHORAX - Chapter 23 (RC122 Respiratory Care Pathophysiology)

Pneumothorax - Comprehensive Study Notes (Chapter 23)

Pneumothorax: General Concepts

  • Definition: A pneumothorax exists when gas accumulates in the pleural space, causing separation of the visceral and parietal pleura.
  • Key signs of pneumothorax:
    • Hyperresonance on percussion on the affected side
    • Decreased or absent breath sounds over the pneumothorax
    • Tracheal deviation can occur in tension pneumothorax (away from the affected side)
    • Pleural air may cause chest pain and dyspnea
  • Pendelluft phenomenon: Paradoxical movement of air within the lungs/chest wall contributing to altered ventilation; linked to chest wall and lung dynamics (referenced with Flail Chest discussion)
  • Initial emergency intervention (for tension/open pneumothorax): Needle decompression in the 2nd intercostal space at the midclavicular line, followed by chest tube thoracostomy
  • Important clinical target: Restore lung expansion and prevent air entry or re-entry into the pleural space

Pneumothorax Classifications

  • General terms:
    • Closed pneumothorax: Gas in pleural space is not in direct contact with the atmosphere
    • Open pneumothorax: Pleural space is in direct contact with the atmosphere; gas can move in and out
    • Tension pneumothorax: A one-way valve effect of ruptured parietal pleura; gas enters during inspiration but cannot exit during expiration; most dangerous form
  • Based on origin:
    • Traumatic pneumothorax: Caused by penetrating wounds (knife, bullet, impaling object)
    • Spontaneous pneumothorax: Occurs without an underlying cause; can be secondary to pneumonia, TB, COPD (blebs/bullae on lung surface can rupture); more common in tall, thin individuals aged roughly 15–35 years
    • Iatrogenic pneumothorax: Occurs during diagnostic or therapeutic procedures

Iatrogenic Pneumothorax (examples)

  • Pleural or liver biopsy
  • Thoracentesis
  • Intercostal nerve block
  • Cannulation of a subclavian vein
  • Tracheostomy (perforation of the posterior tracheal wall can lead to pneumomediastinum)
  • Excessive pressure during mechanical ventilation can cause a pneumothorax
  • Cannot be caused by an endotracheal tube (ET tube) per se

Figures and Illustrations (descriptions)

  • Figure 22-1: Right-side pneumothorax with GA (gas accumulation) and CL (collapsed lung); inset shows atelectasis as a common secondary change
  • Figure 22-2: Sucking chest wound with an open pneumothorax due to traumatic injury
  • Figure 22-3: Closed (tension) pneumothorax produced by chest wall injury
  • Figure 22-4: Right pneumothorax caused by visceral pleural rupture acting as a check valve; progressive enlargement with ipsilateral atelectasis

Pneumothorax Anatomical and Pathophysiological Alterations

  • Lung collapse
  • Atelectasis
  • Asymmetrical chest wall expansion
  • Compression of the great veins and decreased venous return to the heart
  • General consequence: impairment of gas exchange and hemodynamics

Pneumothorax Classifications (Summary)

  • Closed vs Open vs Tension; based on contact with atmosphere and one-way valve mechanism
  • Based on origin: Traumatic, Spontaneous, Iatrogenic

Clinical Manifestations

  • Systemic responses:
    • Increased respiratory rate (RR) due to stimulation of peripheral chemoreceptors
    • Tachycardia (increased HR) and elevated blood pressure (BP)
    • Hypoxemia
    • Pain and anxiety
    • Cyanosis in more severe cases
  • Chest findings:
    • Hyperresonance to percussion on affected side
    • Diminished or absent breath sounds over the affected hemithorax
    • Tracheal shift away from the affected side in tension pneumothorax
    • Possible displacement of heart sounds
  • Pendelluft: paradoxical movement of air between lung regions during respiration; contributes to uneven ventilation

Venous Admixture and V/Q Effects

  • Pendelluft leads to lung collapse and atelectasis, decreasing the V/Q ratio (reduced alveolar ventilation)
  • Resultant intrapulmonary shunting and venous admixture worsen oxygenation
  • PaO2 decreases and peripheral chemoreceptors may be stimulated to increase ventilatory rate

Pulmonary Function Test Findings (PFT)

  • Pattern: Moderate to severe restrictive lung physiology indicated
  • Lung volumes and capacities affected:
    • VT (tidal volume)
    • IRV (inspiratory reserve volume)
    • ERV (expiratory reserve volume)
    • RV (residual volume)
    • VC (vital capacity)
    • IC (inspiratory capacity)
    • FRC (functional residual capacity)
    • TLC (total lung capacity)
    • RV/TLC ratio
  • Overall: reductions across the above parameters consistent with restrictive physiology

Arterial Blood Gases (ABG) – Small Pneumothorax

  • Pattern: Acute alveolar hyperventilation with hypoxemia (acute respiratory alkalosis)
  • Expected trends:
    • pH: ↑ (alkalosis)
    • PaCO2: ↓
    • HCO3-: approximately normal
    • PaO2: ↓
    • SaO2/SpO2: may be reduced or variable

Arterial Blood Gases (ABG) – Large Pneumothorax

  • Pattern: Acute ventilatory failure with hypoxemia (acute respiratory acidosis)
  • Expected trends:
    • pH: ↓
    • PaCO2: ↑
    • HCO3-: ↑ (metabolic compensation over time may occur)
    • PaO2: ↓
    • SaO2/SpO2: ↓

Pneumothorax on Chest X-ray (CXR)

  • Increased translucency (lucency) on the side of the pneumothorax
  • In tension pneumothorax: mediastinal shift away from the affected side
  • Depressed diaphragm on the affected side
  • Associated atelectasis

Case Visuals and Scenarios

  • Figure 22-9 (A and B): Small tension pneumothorax developing in the lower right lung; subsequent mediastinal and cardiac shift with progression
  • Figure 22-10 (A and B): Tall, slender patient with spontaneous left pneumothorax; radiographs show heart mediastinal shift toward the unaffected side as the tension pneumothorax evolves

Pneumothorax – Treatment Thresholds and Options

  • If lung collapse is 15% to 20%: bed rest or limited physical activity; intrapleural gas resorption usually within 30 ext{ days}
  • If lung collapse is > 20%: chest tube insertion (thoracostomy) to evacuate air or needle aspiration
  • Pleurodesis: chemical-induced inflammatory reaction between lung surface and inner chest wall to cause lung to adhere to chest cavity; reduces recurrence risk
  • Oxygen therapy
  • Lung expansion therapy
  • Mechanical ventilation when indicated

Thoracostomy (Chest Tube Insertion) – Procedure and Management

  • Purpose: Create an opening in the chest wall to place a chest tube (thoracic catheter) to allow air and fluid to escape the chest
  • Chest tube is attached to an underwater seal to prevent air re-entry (entrainment) into the lung
  • Suction may be applied; when used, negative pressure should be limited to -12 ext{ cmH}2 ext{O}; -5 ext{ cmH}2 ext{O} is often sufficient
  • After lung re-expansion and cessation of bubbling, leave the tube in place without suction for an additional 24–48 hours

Underwater Seal System (With Chest Tube)

  • Diagrammatic description:
    • From patient -> water seal bottle -> open to air
    • Water level in the seal (typically around 2 ext{ cm}) provides a barrier to entrainment
    • When the patient inspires, the water seal prevents room air from entering the pleural space

Chest Tube – Post-Placement Imaging

  • Chest X-ray confirms tube positioning and lung re-expansion

Pleurodesis (Therapeutic Adherence of Pleura)

  • Talc pleurodesis: Talc is applied between the visceral and parietal pleura
  • Mechanism: Talc induces inflammation and adhesions, sealing the pleural space and preventing recurrent pneumothorax
  • Indicated for recurrent spontaneous pneumothorax or persistent air leaks

Quick Reference – Key Numerical Values (summary)

  • Needle decompression site: 2nd intercostal space at the midclavicular line
  • Chest tube suction limits: -12 ext{ cmH}2 ext{O} (maximum) or -5 ext{ cmH}2 ext{O} (commonly sufficient)
  • Pleural space management thresholds: 15–20% collapse (conservative management) vs >20% collapse (drainage required)
  • Pleurodesis agent: talc (as described)
  • Water seal level in underwater seal: approximately 2 ext{ cm}
  • Time to resorption for small pneumothorax: about 30 ext{ days}
  • Common etiologies: Traumatic, Spontaneous (often in tall/thin individuals aged 15–35 ext{ years}), Iatrogenic

Connections to Practice and Real-World Relevance

  • Recognition of tension pneumothorax requires rapid assessment for tracheal deviation, hypotension, tachycardia, and respiratory distress; immediate decompression is life-saving
  • Differentiating between spontaneous, traumatic, and iatrogenic pneumothorax guides management and prevention of recurrence
  • Understanding pleurodesis helps prevent recurrent pneumothorax in patients with high risk
  • Imaging (CXR) findings guide timing of pleural drainage and monitor progression

Ethical, Philosophical, and Practical Implications

  • Rapid, decisive intervention can be life-saving in tension pneumothorax, highlighting the balance between emergent care and definitive treatment
  • Invasive procedures (chest tubes, pleurodesis) carry risks; patient consent and discussion of recurrence risk and alternatives are important
  • Resource utilization considerations: decisions between observation vs intervention based on percentage collapse and clinical stability