Pneumothorax

Pneumothorax is a medical condition characterized by the presence of air or gas in the pleural cavity, which is the space between the lung and the chest wall. This abnormal accumulation of air can disrupt the normal negative pressure in the pleural space, causing the lung to partially or completely collapse. Pneumothorax can occur spontaneously or as a result of trauma or underlying lung diseases.

1. The presence or absence of an underlying cause:
   • Primary Spontaneous Pneumothorax: Unexpected pleural leakage of air without a preceding lung or pleural disease.
   • Secondary Spontaneous Pneumothorax: Pleural air associated with a preceding lung or pleural disease.
   • Post-Traumatic Pneumothorax: Occurs after blunt or penetrating chest injuries such as rib fractures or crush injuries.
   • Iatrogenic Pneumothorax: Pleural air leakage after diagnostic or therapeutic procedures like thoracocentesis or transbronchial biopsy.
2. The anatomic variety:
   • Open Pneumothorax: Communication between the parenchymal rupture and the pleural cavity remains open, often via a bronchopleural fistula.
   • Closed Pneumothorax: The pleural breach closes after a short time, leading to the absorption of intrapleural gas.
   • Tension (or Valvular) Pneumothorax: A life-threatening emergency where the pleural breach acts as a valve, allowing air into the pleural space during inspiration.

Common types of pneumothorax seen in children include secondary spontaneous pneumothorax, often associated with purulent effusion or empyema (referred to as pyopneumothorax), and pneumothorax associated with transudative pleural fluid collection, known as hydropneumothorax. Malnutrition and measles are common risk factors for pneumothorax in the tropics, particularly beyond the neonatal period.

The presence of air or gas in the pleural cavity results from:

• The permeability of pleural membranes to gas.
• A significant pressure gradient (~68cm H2O) between sub-atmospheric venous blood (73cm H2O) and intra-pleural pressure (5cm H2O).

This gradient facilitates continuous gas absorption from the pleural space into the circulation. Normally, gas diffuses out of the pleural space, maintaining an air-free pleura.

Pleural air accumulation occurs when there's a direct communication between atmospheric air and the pleura. This can happen through:

• Lung parenchyma and visceral pleura.
• Chest wall defects involving parietal pleura connecting the atmosphere to the pleural cavity.

Regardless of age or cause, elevated intrapleural pressure, as seen in tension pneumothorax, leads to:

• Ipsilateral atelectasis due to the inability to counteract elastic recoil with negative subatmospheric intrapleural pressure.
• Contralateral lung hyperinflation.
• Mediastinal shift to the contralateral side, causing venous compression and impaired venous return to the heart.
• Hypoxemia and hypercapnia.

Ventilatory impairment leads to increased inspiratory effort, exacerbating tension pneumothorax and mediastinal shift. Compensatory tachycardia further compromises cardiopulmonary status by reducing venous return and ventricular output.

1. First Breath: Pneumothorax can occur during a baby's first breath.
2. Diagnostic and Therapeutic Manoeuvres: Certain medical procedures can lead to pneumothorax. These include:
   • Thoracocentesis
   • Aspiration lung biopsy
   • Percutaneous pleural biopsy
   • Cardiothoracic surgery
   • Resuscitation
   • Ventilator therapy, especially when using positive end-expiratory pressure (PEEP)
3. Infectious and Respiratory Diseases: Various respiratory conditions and infections can be associated with pneumothorax. These include:
   • Tuberculosis, especially military or cavitatory forms
   • Respiratory distress syndrome
   • Aspiration syndrome
   • Asthma, particularly severe acute asthma
   • Bronchiolitis
   • Pneumonia
   • Measles
   • Pertussis
4. Severe Malnutrition: Pneumothorax may occur in cases of severe malnutrition.
5. Blunt Thoracic Trauma: Trauma to the chest, such as blunt injuries, can lead to pneumothorax.
6. Pulmonary Malignancies: Both primary and metastatic pulmonary malignancies can be associated with pneumothorax.
7. Marfan's Syndrome: Individuals with Marfan's syndrome may be at an increased risk of developing pneumothorax.
8. Cystic Fibrosis: Pneumothorax is relatively common in individuals with cystic fibrosis, especially among Caucasians.

The diagnosis of pneumothorax relies on the patient's history and physical examination. Clinical manifestations vary based on the extent and size of the pneumothorax, whether it is expanding, the degree of lung collapse, and displacement of mediastinal structures.

• Small to Moderate Pneumothoraces (No Mediastinal Shift):
• Symptoms may be minimal or absent.
• Significant or Severe Pneumothoraces:
• Sudden onset of symptoms, including:
• Worsening breathlessness
• Persistent cough
• Pleuritic chest pain (usually severe and localized, sometimes referred to the shoulder tip on the same side due to diaphragmatic pleura irritation)
• Symptoms can be superimposed on underlying lung diseases, such as:
• Necrotizing pneumonia
• Empyema
• Physical findings typically absent in small to moderate pneumothoraces.
• Large Pneumothoraces:
• Central cyanosis
• Chest wall retractions
• Signs of respiratory distress (tachypnea may worsen with increased intrapleural air accumulation)
• Examination of the affected hemithorax reveals:
• Reduced chest movement/expansion
• Tracheal and apical displacement toward the contralateral side
• Decreased tactile fremitus
• Hyperluscent hyper-resonant percussion notes
• Distant or absent breath sounds
• Cardiovascular findings may include:
• Tachycardia (common)
• Pulsus paradoxus
• Hypotension
• Jugular venous distension
• Displaced apex beat
• In newborns, transillumination of the affected side may be positive.
• Abdominal distension can occur due to:
• Increased intrathoracic pressure (causing downward diaphragm displacement)
• Secondary pneumoperitoneum

In tension pneumothorax, a clinical diagnosis is very important, with an immediate need for intervention, as death could occur before a corroborative chest radiograph is done.

Goals of investigation include:

• Confirming the pneumothorax
• Identifying an underlying cause and cardiorespiratory compromise
• Assisting the therapeutic modality

Chest Radiograph: A chest radiograph is usually used to confirm the presence of a pneumothorax. Key findings include:

• An upright chest radiograph in AP and lateral views can detect the presence of small pleural air. Non-loculated air tends to rise to the non-dependent part of the pleural cavity.
• The air in the pleural space is visible on the radiograph as hyperlucency of the vascular and lung markings on the affected side.
• Features of atelectasis may be seen on the affected side.

In a large pneumothorax:

• There is an absence of lung markings between the well-defined edge of the collapsed lung and the chest wall.
• There may be a shift of the trachea and mediastinal structures away from the affected side.

In infants, chest radiographs are usually taken in the supine position. A small pneumothorax can be more easily detected in the lateral decubitus view with the affected side up.

Chest radiographs can also confirm underlying pulmonary lesions, such as pneumonia with or without pneumatocoeles, pleural effusion, or a rib fracture.

Serial chest radiographs are invaluable for monitoring therapeutic response and identifying continuous air leakage or tension pneumothorax. They reveal worsening lung collapse and a shift of mediastinal structures occurring over a short time.

Chest CT Scan: While not recommended for routine use, a chest CT scan is the most reliable radiologic method for confirming a pneumothorax. It is particularly useful in the following situations:

• Identifying multiple blebs and bullae
• Differentiating large bullae and emphysematous lung from a pneumothorax

Arterial Blood Gas (ABG) and Pulse Oximetry Measurement: These tests are important for patients presenting with respiratory distress. A ventilation-perfusion mismatch often leads to hypoxemia in these patients. ABG analysis helps identify acidaemia, hypercarbia, and hypoxemia. These tests are crucial for monitoring the patient's response to therapy.

Chest Transillumination: In some cases, pneumothorax can be detected using chest transillumination with a powerful fiber optic light probe. However, such equipment may be difficult to obtain in tropical regions.

Pneumothorax can lead to various complications and clinical syndromes, including:

• Related to the Pneumothorax:
• Increasing lung compression and collapse
• Severe mediastinal shift with the risk of kinking great vessels
• Hypoxemic respiratory failure
• Cardiac arrest
• Bronchopleural fistula
• Air leak syndromes like interstitial and subcutaneous emphysema
• Pneumomediastinum
• Pneumopericardium
• Pneumoperitoneum
• Pulmonary pseudocyst
• Pyopneumothorax
• Pulmonary edema following lung re-expansion
• Related to Chest Tube Insertion:
• Bleeding
• Infection
• Incorrect tube placement (inferiorly) with possible diaphragmatic or abdominal viscera injury
• Pain at the site of chest tube insertion
• Persistent air leak
• Prolonged tube drainage and hospital stay

Pneumothorax should be differentiated from other conditions, including:

• Compensatory hyperinflation (with contralateral lung collapse)
• Diaphragmatic hernia
• Congenital lobar emphysema
• Congenital cystic lesions of the lung

The goals of treatment for pneumothorax are to facilitate rapid reabsorption of the pneumothorax, ensuring an air-free pleural space, and to restore lung volume. The choice of treatment modality depends on several factors:

• Size of the Pneumothorax: Treatment approach varies based on the size of the pneumothorax.
• Recurrence: Whether the pneumothorax is recurrent or not.
• Features of Tension Pneumothorax: Presence of tension pneumothorax features.
• Severity of Underlying Disease: Severity of the underlying disease and respiratory distress.

Generally, the size of the pneumothorax is determined by the percentage of the hemithorax it occupies.

Conservative Care

A conservative approach is preferred when dealing with a small closed pneumothorax:

• Treatment of the underlying condition, such as antibiotic therapy for Staphylococcal pneumonia.
• Analgesia/sedation with a mild narcotic like codeine.
• Encouraging frequent small-volume feeds, especially in neonates.
• Careful inpatient monitoring for signs of progressive cardiorespiratory deterioration, including blood gases or hemoglobin oxygen saturation.
• Administration of supplemental 100% oxygen, typically at a high flow rate (5-10L/min), to treat hypoxemia and aid in pleural air absorption (resulting in a 4-fold increase compared to room air).

Specific Restoration of Air-free Pleural Options

Indications for specific restoration of an air-free pleural cavity include:

• Tension pneumothorax
• Worsening severity of an open or closed variety
• Recurrence
• Increasing radiologic size
• Failure to achieve a prompt resolution with time
• Reduction in volume by ≥ 50% in a dyspnoeic child

These options include mechanical evacuation of trapped air via needle aspiration, using a one-way valve system, or an underwater-sealed thoracostomy tube drainage system.

A prompt mechanical evacuation, especially to relieve tension pneumothorax, can be achieved by direct needle aspiration at the second or third intercostal space (midclavicular or anterior axillary line) using an 18G needle and 20ml or 50ml syringe initially. Subsequently, a catheter is attached and connected to one of the following:

• A one-way flutter valve (Heimlich valve)
• An underwater-sealed drainage system

In cases of recurrent pneumothoraces, such as those in malignancies, cystic fibrosis, or congenital lesions, alternative treatment options may be considered:

• Open but limited thoracotomy
• Video-assisted thoracoscopic surgery (VATS)

These procedures aim to effect the closure of fistulas, pleural stripping to ensure subsequent adhesions, and plication of emphysematous blebs.

Pleurodesis

Pleurodesis is a non-surgical specific treatment option used in poorly resolving pneumothorax after a 2-3 month duration or recurrent pneumothorax. It involves the intra-pleural instillation of agents like quinacrine hydrochloride in saline (100mg in 15 ml of saline). Please note that pleurodesis is contraindicated if a lung transplant is indicated and being contemplated subsequently.

Treatment of Complications and Comorbidities

Here are some approaches to treat complications and comorbidities associated with pneumothorax:

• Interstitial Emphysema: Increasing the concentration of inspired oxygen and, in neonates on artificial ventilation, reducing ventilatory pressure.
• Surgical Removal of Loculated Gas: This may eventually be necessary, particularly in ventilator-treated preterm infants with persistent interstitial emphysema complicating respiratory distress syndrome.
• Pneumopericardium: Lowering the inspired ventilatory flow rate and/or pericardiocentesis to relieve pericardial tamponade may be necessary in those with complicating pneumopericardium.
• Subcutaneous Emphysema: This should resolve with addressing the underlying condition and the administration of supplemental oxygen.

The outcome of the disease depends on:

• The anatomic type/severity (tension pneumothorax is potentially fatal)
• Underlying parenchymal disease
• The promptness of the diagnosis and therapeutic intervention