Spontaneous pneumothorax

Notes

Introduction

A pneumothorax is a collection of air within the pleural space.

The pleural space (or cavity) refers to the space between the parietal (lines the inner wall of the lung) and visceral pleura (lines the surface of the lung). When air enters this space it is referred to as a pneumothorax.

Pleural anatomy

There are two major types of pneumothorax:

  • Spontaneous: occurring without prior trauma, normally in older patients with underlying lung disease or younger patients with apical blebs.
  • Traumatic: occurring in the setting of trauma, may be open (direct communication between the outside air and pleural space) or closed.

Aetiology

Spontaneous pneumotharaces may be either primary or secondary

First described in the early nineteenth century, pneumothorax was most commonly seen in patients with pulmonary tuberculosis.

Today in the UK pulmonary TB is relatively rare, instead other forms of lung disease are related to pneumothorax (secondary). It may also be seen in patients with healthy lungs (primary):

  • Primary spontaneous pneumothorax (PSP) - occur spontaneously in a previously non-pathological lung; typically seen in tall, thin young men.
  • Secondary spontaneous pneumothorax (SSP) - occur in previously diseased lungs; common causes include COPD and asthma.

It is thought that in both types the underlying mechanism is due to the rupture of lung blebs and bullae. These are small pockets of air that form within the lung parenchyma.

Imaging

If the patient presents with features of tension pneumothorax, imaging must not delay urgent decompression.

Chest radiograph

Erect chest x-ray is the standard first line imaging, allows size of pneumothorax to be estimated. A subtle pneumothorax may be missed and quantification of size may be inaccurate.

Of note supine radiographs are less sensitive, CT or USS should be considered in patients unable have an erect film.

Be aware, severe bullous lung may be mistaken as a pneumothorax. Placing a chest drain into a bullae has disastrous consequences. If diagnostic uncertainty exists review with a senior physician and consider a CT chest.

Left sided pneumothorax

AP chest radiograph demonstrating a spontaneous left-sided pneumothorax

Image courtesy of Hellerhoff

USS

May be of use in trained hands, however is typically used in the trauma setting to complete a FAST scan. Therapeutically may be used to aid drain placement.

CT Chest

Increasingly used and can be considered the gold-standard. Identifies subtle pneumothoraces and allows accurate estimation of the size.

Essential in cases with diagnostic uncertainty. May be used by interventional radiologist to place chest drains in the presence of significant bullae or surgical emphysema.

Size estimation

Size of a spontaneous pneumothorax helps to guide its management.

The 2010 British Thoracic Society guidelines advise measurement at the level of the hilum. A cut-off of 2cm, between the chest wall and margin of the lung at this level, differentiates radiographically between ‘small’ and ‘large’ pneumothoraces. 

Apex-cupola distance and inter-pleural distance in pneumothorax

CT scanning may be used to obtain truly accurate measurements.

It is important to recognise that size of the pneumothorax does not always correlate well with degree of clinical compromise.

Tension pneumothorax

Tension pneumothorax represents a medical emergency requiring prompt recognition and treatment.

Tension occurs when a ‘one way valve’ system allows air into the inter-pleural space but does not let it escape. This results in increasing pressures, which impair venous return to the heart, compromising cardiac output. 

If the diagnosis is made, adminster high flow oxygen and carry out urgent needle decompression, imaging should not be awaited. This cannula should be left in place until a chest drain is correctly placed.

Symptoms

  • SOB
  • Chest pain

Signs

  • Respiratory distress
  • Tachypnea 
  • Hypoxaemia 
  • Haemodynamic instability (tachycardia, hypotension)

Lateralising signs

  • Decreased air entry
  • Tracheal deviation (away from affected side)
  • Hyperresonance

Remember tension pneumothorax may present in a range of clinical settings including the inpatient population. Patients receiving NIV, mechanical ventilation may be at risk. It may also occur due to blocked or malpositioned chest drains.

Clinical features of pneumothorax

Management

Treatment should be guided by the patients symptoms and radiological findings.

Primary spontaneous pneumothorax

  • Large (>2cm) or breathless:
    •  It is advised that people with large pneumothoraces or are breathless undergo active intervention. Needle aspiration (14-16G needle) is typically advised first as it has been shown to be effective and is associated with a decreased length of stay when compared to a chest drain. Stop after 2.5L has been aspirated. 
    • If needle aspiration fails a small bore (<14 F) Seldinger chest drain can be inserted. All patients with a chest drain must be admitted and referred to local specialists.
    • Some patients with large pneumothoraces whom are asymptomatic may be managed conservatively. This should be decided with specialist input.
  • Small (<2cm) and asymptomatic: 
    • Observation with outpatient follow-up is appropriate for small (<2cm) pneumothoraces with minimal symptoms.
    • Patients should be advised to return if they develop breathlessness. Admit for observation if unable to comply with such advice.

All patients should be referred to respiratory specialists and have specialist follow-up. Many will advise routine supplemental oxygen.

Secondary spontaneous pneumothorax

  • Large (>2cm) or breathless: Place a small bore (<14 F) Seldinger chest drain. 
  • Size 1-2cm: Needle aspiration (14-16G needle) is typically advised first as it has been shown to be effective and is associated with a decreased length of stay when compared to a chest drain. Stop after 2.5L has been aspirated.
  • Size < 1cm: Admit and observe for at least 24h, consider supplemental oxygen.

Consider drain placement under CT guidance if technically challenging. All patients should be referred to respiratory specialists. If air leak is persistent beyond 48 hours discuss with thoracic surgery.

Management of the spontaneous pneumothorax

Referral to thoracic surgery

Patients with persistent air leak should be referred to thoracic surgeons for an opinion. It should however be noted that it may take 14 days for air leak from primary pneumothoraces to resolve with chest drain management. 

Other reasons to refer to thoracic surgeons include:

  • Ipsilateral recurrence
  • Bilateral (synchronous) pneumothoraces
  • Contralateral non-synchronous pneumothoraces
  • Pregnancy
  • At risk occupations (e.g. pilots)

Further advice

At discharge, clear advice to return if they develop breathlessness or chest pain should be given.

Patients should be booked respiratory follow-up at discharge. All should be followed up until full resolution. Smoking is associated with recurrence and cessation support should be offered.

Flights must be avoided until complete resolution. Most would advise at least two weeks after successful treatment and re-expansion.

Patients are advised to permanently avoid diving. Diving may be possible after successful surgical intervention with normal post-operative tests. This should be guided by respiratory specialist.

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