Pneumothorax

Pneumothorax 

1. Definition

Pneumothorax is the presence of air in the pleural space, resulting in partial or complete lung collapse due to loss of negative intrapleural pressure.

In the ICU, pneumothorax is particularly important because it may occur due to:

• Mechanical ventilation
• Procedures (central line, thoracentesis)
• Trauma
• Underlying lung disease

The most dangerous form is tension pneumothorax, which causes obstructive shock and cardiac arrest if untreated.

2. Relevant Pleural Physiology

Normal Pleural Pressure

Negative pressure keeps the lung expanded against the chest wall.

When Pneumothorax Occurs

Air enters pleural space → pressure becomes less negative or positive → lung collapses.

Consequences:

• ↓ Lung compliance
• ↓ Vital capacity
• ↑ Shunt
• Hypoxemia

3. Classification of Pneumothorax

3.1 Based on Etiology

A. Spontaneous Pneumothorax

1. Primary Spontaneous Pneumothorax (PSP)

Occurs without known lung disease.

Risk factors:

• Tall thin males
• Smoking
• Apical blebs rupture

Typical age: 20–30 years

2. Secondary Spontaneous Pneumothorax (SSP)

Occurs in patients with underlying lung disease.

Common causes:

SSP is more dangerous because patients already have poor lung reserve.

B. Traumatic Pneumothorax

Occurs due to injury to chest wall or lung.

Causes

Blunt trauma

• Rib fracture
• Pulmonary laceration

Penetrating trauma

• Stab injury
• Gunshot wound

C. Iatrogenic Pneumothorax

Very common in ICU.

Causes include:

D. Barotrauma-Related Pneumothorax (ICU)

Occurs in:

• ARDS
• Mechanical ventilation
• High PEEP
• High tidal volume
• High plateau pressure

Mechanism:

Alveolar rupture → air dissects along bronchovascular sheath → pleural space.

4. Types of Pneumothorax

4.1 Simple Pneumothorax

Air enters pleural space but no progressive pressure build-up.

Features:

• Lung collapse
• No mediastinal shift
• Hemodynamics stable

4.2 Open Pneumothorax

Also called sucking chest wound.

Chest wall defect allows air to move freely between:

• pleural space
• atmosphere

Air enters through chest wall instead of trachea.

4.3 Tension Pneumothorax 

Life-threatening emergency.

Mechanism:

One-way valve effect

Air enters pleural space during inspiration but cannot escape during expiration.

Consequences:

• Increasing intrathoracic pressure
• Lung collapse
• Mediastinal shift
• Compression of vena cava
• ↓ venous return
• Obstructive shock

Hemodynamic Effects

4.4. Pneumothorax Size Definition

According to British Thoracic Society:

Alternative method (ACCP):

Distance from apex to cupola >3 cm = large pneumothorax.

 Pneumothorax Severity (British Thoracic Society)

5. Clinical Features

Symptoms

• Sudden chest pain
• Dyspnea
• Tachypnea
• Anxiety

Signs

Classical Signs of Tension Pneumothorax

• Severe dyspnea
• Hypotension
• Distended neck veins
• Tracheal deviation
• Absent breath sounds

However in ICU these may be subtle or absent.

6. Pneumothorax in Mechanically Ventilated Patients

7. Diagnosis

 Chest X-ray

Most common test.

Classic signs:

• Visible pleural line
• No lung markings peripheral to line
• Lung collapse

Signs on Supine X-ray (ICU)

Harder to detect.

Look for:

 Lung Ultrasound (Preferred ICU Test)

Extremely sensitive.

Normal Lung US

Findings:

• Lung sliding
• B-lines

Pneumothorax Findings

Lung Point

Transition between:

• normal lung sliding
• absent sliding

Highly specific for pneumothorax

M-mode Ultrasound Signs

 CT Scan

Gold standard.

Indications:

• Uncertain diagnosis
• Trauma
• Small pneumothorax

8. Management Principles

Management depends on:

• Size
• Symptoms
• Stability
• Mechanical ventilation

Primary Spontaneous Pneumothorax

Secondary Spontaneous Pneumothorax

More aggressive treatment.

Oxygen Therapy

High-flow oxygen accelerates air absorption.

Mechanism:

Reduces nitrogen partial pressure in alveoli, increasing gradient for nitrogen absorption from pleural space.

Follow-up imaging:

• Chest X-ray after 6 hours

9.  Emergency Management

If Tension Pneumothorax Suspected

DO NOT WAIT FOR X-RAY

Immediate needle decompression.

Needle Decompression

Sites

Procedure

Large bore needle (14–16G).

Insert above rib → air release.

Temporary measure → chest tube required.

Problems with Needle Thoracostomy

Studies show failure rate up to 40–50% due to:

• Thick chest wall
• Short cannula
• Kinking
• Incorrect site

Hence many trauma guidelines prefer finger thoracostomy(5th ICS anterior axillary).

10. Chest Tube (Tube Thoracostomy)

Definitive management.

Site

Triangle of Safety

Boundaries:

• Anterior border of latissimus dorsi
• Lateral border of pectoralis major
• Line superior to nipple
• Apex below axilla

Tube Size

Mechanism

Tube connected to:

• underwater seal
• suction

Allows continuous evacuation of air.

11. Ventilator Management

Important in ICU pneumothorax.

Strategies:

12. Persistent Air Leak

Defined as air leak >5–7 days.

Causes:

• bronchopleural fistula
• lung necrosis
• ARDS

Management

Options:

13. Complications

14. Re-Expansion Pulmonary Edema

Occurs after rapid re-expansion of collapsed lung.

Mechanism:

• capillary leak
• inflammatory injury

Risk factors:

• large pneumothorax
• 3 days duration

Prevention

Drain slowly.

15. Recurrence Prevention

Used in recurrent pneumothorax.

Options:

16. Pneumothorax vs Hemothorax vs Pleural Effusion

Guidelines mainly derived from:

• British Thoracic Society (BTS) 2023
• American College of Chest Physicians (ACCP)