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Pneumothorax

Note: Davidson's Principles and Practice of Medicine is not in this textbook library. The following is a comprehensive clinical overview drawn from Murray & Nadel's Textbook of Respiratory Medicine and Harrison's Principles of Internal Medicine 22E (2025) - both cover the same content as Davidson's on this topic.

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Definition

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Classification

1. Spontaneous Pneumothorax

• Occurs without underlying lung disease or antecedent trauma
• Typical patient: tall, thin young male, often a smoker
• Due to rupture of apical pleural blebs - small cystic spaces (outpouchings of visceral pleura, <1 cm) that lie within or immediately under the visceral pleura
• Blebs vs. Bullae: A bleb (<1 cm) is an outpouching between the lamina elastica interna and externa; a bulla (>1 cm) is an airspace demarcated by a thin wall (Reid classified bullae into 3 types)
• Microscopic abnormalities include respiratory bronchiolitis and pleural fibroelastosis
• Smoking is a major risk factor (airway inflammation weakens the visceral pleura)
• ~50% of patients will have a recurrence after the first episode

• Occurs in the context of underlying lung disease
• More dangerous because of reduced pulmonary reserve
• Causes (Murray & Nadel's):

• Catamenial pneumothorax: Recurrent pneumothorax in women of childbearing age - consider thoracic endometriosis
• LAM: Spontaneous pneumothorax in younger women (30-40 years) may be the first manifestation

2. Traumatic Pneumothorax

• Results from penetrating or nonpenetrating chest injuries
• Present in 40% of blunt and 20% of penetrating thoracic trauma cases
• Iatrogenic causes: transthoracic needle aspiration, thoracentesis, central venous catheter insertion (most common iatrogenic causes)
• Open pneumothorax ("sucking chest wound"): chest wall defect allows air entry through the wound; if wound approaches the size of the trachea, ventilation is severely compromised
  • Management: cover with a one-way flutter (Heimlich) valve or occlusive dressing with one side open before operative repair

3. Tension Pneumothorax

• A medical emergency
• One-way valve mechanism: air enters but cannot escape - progressive intrapleural pressure rise
• Compresses the right ventricle, kinks the SVC/IVC, reduces venous return and cardiac output
• Causes obstructive shock: hypotension + hypoxia
• Hypoxemia is nearly universal (92%) in ventilated patients; present in only 50% breathing unassisted
• Treatment must not wait for radiologic confirmation - immediate thoracic decompression

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Clinical Features

• Symptoms: Sudden onset ipsilateral pleuritic chest pain and breathlessness; may be minimal in small PSP
• Signs:
  • Reduced chest expansion on affected side
  • Hyperresonant percussion note
  • Diminished/absent breath sounds
  • Tracheal deviation away (in tension - a late sign)
• In tension: hypotension, tachycardia, raised JVP, cyanosis

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Diagnosis

Chest X-Ray

• Gold standard for diagnosis
• Visible lung edge with absent lung markings peripherally
• BTS size classification: small (<2 cm rim of air at the hilum), large (≥2 cm)
• Note: Three different guidelines classify size differently with agreement in only 47% of cases

CT Chest

• More accurate for size estimation
• Identifies underlying lung disease, blebs, bullae
• Useful before surgical intervention

Ultrasound (POCUS)

• Pleural sliding (sea-shore sign on M-mode): when present, effectively excludes pneumothorax at that location
• Absence of sliding is not specific (also seen in apnea, pleural adhesions)
• "Lung point" (transition from sliding to no sliding at the edge of the pneumothorax): highly specific for pneumothorax
• B-lines: if present, excludes pneumothorax at that site
• "Bar code" / "stratosphere" sign (M-mode): linear pattern throughout depth - seen when sliding is absent
• More sensitive than CXR for occult pneumothorax, particularly in trauma

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Management

Primary Spontaneous Pneumothorax

• Supplemental O₂ accelerates resolution of pneumothorax
• Needle aspiration vs. chest tube: Multiple RCTs show comparable initial success rates (aspiration 48-80%; chest tube 64-100%)
• Ambulatory management: One-way (Heimlich/flutter) valve attached to chest drain; effective in 85.8% - reduces hospital stay vs. standard chest drain (median 8 days hospitalized vs. outpatient)

Secondary Spontaneous Pneumothorax

• Nearly all patients require tube drainage
• Many will need thoracoscopy/thoracotomy with stapling + surgical pleurodesis
• If not a good operative candidate: chemical pleurodesis

Tension Pneumothorax

• Immediate decompression: needle thoracostomy or tube thoracostomy
• ATLS recommendations: insert needle at 4th-5th intercostal space, midaxillary line (higher success rate than traditional 2nd ICS midclavicular line due to thinner chest wall, avoids internal mammary/subclavian artery injury)
• A 5-cm angiocatheter at the anterior axillary line 4th-5th ICS has significantly lower failure rate (13% vs. 38% at midclavicular 2nd ICS)
• Follow immediately with chest tube

Traumatic Pneumothorax

• Usually treated with tube drainage unless very small
• Hemopneumothorax: one tube superiorly (air) + one inferiorly (blood)
• Iatrogenic: often managed with supplemental O₂ or aspiration; tube drainage if these fail

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Prevention of Recurrence / Pleurodesis

• Talc poudrage: 2-4 g sufficient; no long-term sequelae (lung function near-normal 22-35 years later); relative contraindication if future lung transplant is anticipated (but not absolute)
• VATS: Important disadvantage - long-term postoperative pain (>30% patients, lasting 3-18 months)
• Mechanical pleurodesis: abrasion or partial parietal pleurectomy
• Bulectomy alone has unacceptably high recurrence (27.5% at 10 years) - must add pleurodesis

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Complications

• Re-expansion pulmonary edema (RPE): Unilateral pulmonary edema after rapid lung reinflation; incidence ~1-3% symptomatic; treat with supplemental O₂ and diuretics
• Haemopneumothorax: Blood + air in pleural space (from torn adhesions or vascularized bullae rupture)
• Persistent air leak (bronchopleural fistula)
• Tension pneumothorax (if untreated)

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Special Situations

• Air travel: Pneumothorax may expand at altitude (reduced cabin pressure) - patients should not fly until fully resolved
• Diving: Absolute contraindication until definitive treatment (surgical pleurodesis) given risk of rapid expansion at depth

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🫁 Pneumothorax - A Complete Teaching Session

Sources: Murray & Nadel's Textbook of Respiratory Medicine (Chapter 110) | Harrison's Principles of Internal Medicine 22E

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LECTURE 1: What Is a Pneumothorax?

Definition: Pneumothorax = air in the pleural space, causing partial or complete lung collapse.

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LECTURE 2: How Does It Start? (Pathophysiology)

The Culprit: Blebs and Bullae

Why Do Blebs Form?

• Smoking causes small airways inflammation → weakens the visceral pleura or dilates distal airways → increased airway pressure
• Matrix metalloproteinases (MMP-2, MMP-7, MMP-9) are overexpressed in PSP patients, damaging the basement membrane
• "Pleural porosity" - microscopic pores in the pleura may leak air even when no visible bleb ruptures (Noppen's fluorescence study showed high-grade porosity only in PSP patients)

Teacher's pearl: Bleb rupture was the classic explanation, but we now know many patients have NO visible bleb at thoracoscopy. The concept of diffuse pleural porosity is actually more important than bleb rupture alone.

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LECTURE 3: Classification - The Big Picture

PNEUMOTHORAX
├── SPONTANEOUS (no trauma)
│   ├── PRIMARY (PSP) - no underlying lung disease
│   └── SECONDARY (SSP) - underlying lung disease
├── TRAUMATIC
│   ├── Penetrating / Blunt
│   ├── Iatrogenic
│   └── Open (sucking chest wound)
└── TENSION - life-threatening emergency

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LECTURE 4: Primary vs Secondary - Who Gets It?

Primary Spontaneous Pneumothorax (PSP)

Secondary Spontaneous Pneumothorax (SSP)

Teacher's tip: Two clinical pearls worth memorising:

1. Young woman (30-40 yrs) + recurrent PTX → think LAM (lymphangioleiomyomatosis) - PTX may be the first presentation
2. Recurrent PTX in woman of childbearing age, timed with menstruation → think Catamenial pneumothorax (thoracic endometriosis)

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LECTURE 5: Clinical Features - How Does the Patient Present?

Symptoms

• Sudden onset pleuritic chest pain (ipsilateral)
• Breathlessness (proportional to size and underlying lung reserve)
• May be asymptomatic in small PSP in a young healthy person

Signs (from the affected side)

1. Increased hemithorax size (expanded chest wall due to air)
2. Decreased expansion on the affected side
3. Hyperresonant percussion (tympany - air doesn't dampen the sound)
4. Absent/diminished breath sounds

Signs of TENSION (emergency!)

• All of the above PLUS:
• Tracheal deviation away from the affected side
• Raised JVP (obstruction of venous return)
• Hypotension + tachycardia (obstructive shock)
• Cyanosis

Remember: Tracheal deviation is a LATE sign. Don't wait for it. If a patient has hypotension + absent breath sounds on one side after trauma or in ICU on a ventilator, assume tension until proven otherwise and decompress immediately.

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LECTURE 6: Diagnosis - What Do You See on Imaging?

Chest X-Ray (CXR) - Your First Tool

How to Distinguish PTX from a Skinfold (Common exam trap!)

The Deep Sulcus Sign (Supine Patient)

Ultrasound (POCUS) - Increasingly Important

Ultrasound sensitivity is 78-90% vs CXR sensitivity 39-52% for PTX - especially in supine trauma patients.

CT Chest - The Gold Standard for Sizing and Differentiation

BTS Size Classification (used clinically)

• Small: rim of air < 2 cm at the hilum level
• Large: rim of air ≥ 2 cm

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LECTURE 7: The Life-Threatening Emergency - Tension Pneumothorax

Visceral pleural tear acts as ONE-WAY VALVE
         ↓
Air enters pleural space with each breath
Air CANNOT escape (valve closes on expiration)
         ↓
Progressive rise in intrapleural pressure
         ↓
Compresses RIGHT VENTRICLE
Kinks / compresses SVC + IVC
         ↓
↓ Venous return → ↓ Cardiac output
         ↓
OBSTRUCTIVE SHOCK: Hypotension + Hypoxia

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LECTURE 8: Management - A Structured Approach

Primary Spontaneous Pneumothorax (PSP)

PSP diagnosed on CXR
       │
       ├─── Clinically stable + SMALL (< 2 cm)
       │          │
       │      CONSERVATIVE: Observation + High-flow O₂
       │      (O₂ accelerates reabsorption ~4x)
       │      Can be managed as OUTPATIENT
       │
       └─── Symptomatic OR LARGE (≥ 2 cm)
                  │
             First-line: NEEDLE ASPIRATION
             (or tube drainage)
                  │
             Lung re-expands? → Discharge + follow up
                  │
             Fails / Recurrence?
                  │
             THORACOSCOPY + bleb stapling + PLEURODESIS

Secondary Spontaneous Pneumothorax (SSP)

Tension Pneumothorax

Open Pneumothorax (Sucking Chest Wound)

• Immediate management: Cover with a Heimlich (flutter) valve or 3-sided occlusive dressing (allows air out, not in)
• Definitive: Surgical repair

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LECTURE 9: Preventing Recurrence - Pleurodesis

Talc safety: In long-term follow-up (22-35 years after talc poudrage), patients had near-normal lung function (TLC ~89% predicted) and no mesothelioma was observed. Talc is relatively contraindicated - not absolutely - in future lung transplant candidates.

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LECTURE 10: Complications to Know

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Quick Exam Summary

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