Pneumothorax

A pneumothorax refers to a collection of gas in the pleural space resulting in collapse of the lung on the affected side. The extent of the collapse of the lung is dependent upon the amount of air that is present. Pneumothorax can be classified according to aetiology:

• Primary spontaneous pneumothorax occurs with no previous lung disease but there are tiny blebs that are foci of weakness. It usually affects a young adult.
• Secondary spontaneous pneumothorax occurs in slightly older subjects with underlying lung disease. It usually follows rupture of a congenital bulla or a cyst in chronic obstructive pulmonary disease (COPD).
• Traumatic pneumothorax follows a penetrating chest trauma such as a stab wound, gunshot injury or a fractured rib.
• Iatrogenic pneumothorax may follow a number of procedures such as mechanical ventilation and interventional procedures such as central line placement, lung biopsy and percutaneous liver biopsy.
• Catamenial pneumothorax refers to pneumothorax at the time of menstruation.¹ The aetiology is endometriosis. It represents 3 to 6% of spontaneous pneumothorax in women. Patients are typically aged 30 to 40 years with a history of pelvic endometriosis in 20 to 40%. Over 90% occur in the right lung and it occurs within 72 hours from the onset of menstruation. In women receiving hormonal treatment, 50% will have a recurrence within a year.

• The incidence of spontaneous primary pneumothorax is 18 per 100,000 men per year and 6 per 100,000 women per year.²
• It occurs most often in the 20s, and primary spontaneous pneumothorax rarely occurs over the age of 40.
• Secondary spontaneous pneumothorax typically occurs between 60 and 65.
• Between 1991 and 1995 the rate of admissions to UK hospitals for both primary and secondary spontaneous pneumothorax was 16.7 per 100,000 men per year and 5.8 per 100,000 women per year.³
• Recurrence will occur in about 30% of primary and 45% of secondary pneumothorax. It often occurs within 6 months, and usually within 3 years.

Risk factors

• Thoracoscopy and CT scans have shown that the vast majority of primary spontaneous pneumothorax are caused by subpleural blebs and bullae.
• Those affected tend to be tall young men. Marfan's syndrome or a Marfan's habitus increase the risk.
• Smoking markedly increases the risk by about 22-fold in men and 8-fold in women and there is a dose related response in that heavier smokers are at greater risk.²
• Although there is usually no known lung disease, in 80% of patients a CT scan will show areas of emphysema in the upper zones.
• Secondary spontaneous pneumothorax can occur with tuberculosis, sarcoidosis, cystic fibrosis, malignancy, and idiopathic pulmonary fibrosis. It may also occur with Pneumocystis carinii infection in AIDS.
• Familial predisposition to pneumothorax has been described with both autosomal dominant of limited penetrance and X-linked recessive variants.⁴

• Spontaneous pneumothorax usually occurs at rest.⁵
• Sudden onset of pain is typical.
• There may well be some shortness of breath, depending upon the size of the lesion. It tends to be more severe in secondary pneumothorax as there is less reserve.
• Around two thirds of patients will have both pain and dyspnoea.

Examination

• The patient often looks distressed and is sweating. Dyspnoea may be apparent and even cyanosis, depending upon the degree of respiratory inadequacy.
• Pulse examination:
  • Tachycardia is common but a pulse rate above 135 per minute suggests tension pneumothorax.
  • Pulsus paradoxicus suggests a severe pneumothorax. Pulsus paradoxicus is when the pulse slows on inspiration. This is the opposite to sinus arrhythmia where there is a slight acceleration of the pulse with inspiration.
• Hypotension may occur and JVP may be raised, especially in tension pneumothorax.
• Examination of the chest may show that the affected side moves less than the normal side. The best way to elicit this is to place your hands on each side of the patient's chest and to feel the movement when you ask him to take a deep inspiration.
• The trachea is deviated away from the side of collapse especially in tension pneumothorax.
• Percussion reveals hyper-resonance over the collapse.
• Breath sounds are reduced or absent over the affected area.
• Bilateral pneumothorax is unusual but the lack of asymmetry of the chest will make clinical diagnosis more difficult.
• There are specific problems for those who are being ventilated. High peak airways pressure suggests an impending pneumothorax. There will be difficulty ventilating the patient during resuscitation. A tension pneumothorax causes progressive difficulty with ventilation as the normal lung is compressed.

• Chest x-ray:
  • Chest x-ray should show a clear line of visceral pleura with absence of peripheral lung markings beyond it. The trachea and mediastinum may also be deviated to the contralateral side.
  • Errors can arise from mistaking skin folds and the scapula for a pleural edge. They tend to lack the characteristic rounded appearance.
  • In supine patients, a deep sulcus sign with radiolucency along the costophrenic sulcus may help to identify an occult pneumothorax. In supine patients look for the line of pneumothorax at the base of the lungs or close to the heart.
  • It is traditionally recommended that it is easier to detect a pneumothorax with the picture in full expiration instead of the usual full inspiration as for all other films. This has been disputed.⁶
• Arterial blood gases will show hypoxia, the degree being dependent upon the severity of the condition. It tends to be more disturbed in secondary spontaneous pneumothorax as there is less reserve in the presence of pre-existing lung disease.
• CT is not used as a matter of routine but may be helpful to differentiate a large bulla from a pneumothorax, to indicate other pathology such as emphysema and sometimes in ventilated patients.
• To calculate the size of a pneumothorax: a technique recommended by the British Thoracic Society is to measure the distance between the pleural surface and the lung edge. If this is 2cm or more it represents a pneumothorax of at least 50% of the hemithorax and is an indication for drainage.⁷

• Pleural effusion tends to be slower in onset and there is dullness on percussion.
• Chest pain: a pleuritic pain may give a sensation of breathlessness. Examples include pleurodynia and Bornholm disease.
• Pulmonary embolism may produce haemoptysis and a few rales over the affected area. It more commonly affects the lower rather than the upper lungs.

• Simple observation, needle aspiration and chest drain are all possibilities and the choice will depend upon the severity of the condition.
• Secondary spontaneous pneumothorax and traumatic pneumothorax usually require active treatment.
• Iatrogenic pneumothorax does not normally require a chest drain.
• Tension pneumothorax requires immediate attention.

Immediate management

• Oxygen should be given. This helps relieve hypoxia and it accelerates resorption of the pneumothorax compared with breathing air.
• A small pneumothorax of 15% or less can be managed by observation, using both clinical assessment and chest x-ray to ascertain that it is not enlarging.
• Larger lesions can be treated by simple aspiration, also called thoracentesis:
  • The puncture site is commonly in the second or third intercostal space in the midclavicular line or in the fourth or fifth intercostal space over the superior rib margin in the anterior axillary line.
  • The skin is prepared with antiseptic and local anaesthetic given to infiltrate the skin and underlying tissues.
  • Entry should be just above a rib rather than just below it so as to reduce the risk of hitting the neurovascular bundle.
  • A needle with plastic catheter, as for intravenous infusion, is used. It is attached to a 3-way stopcock and a large syringe. It is used to suck out as much air as possible or if the patient suddenly coughs, it has achieved its purpose.
  • The needle is withdrawn and the site massaged and "plastic skin" may be used to seal the hole.
  • Repeat chest x-ray is required.
  • Aspiration is a newer technique than chest drain but may be as effective as a drain in moderate size first occurrences.⁸ It can even be used without admitting the patient to hospital but all patients who have had a pneumothorax should receive written instructions that if they develop sudden shortness of breath they must return immediately.
• A chest drain tube is usually required for spontaneous secondary pneumothorax and for all large lesions:
  • The technique is similar to chest aspiration except that the tube is kept in situ.
  • A small bore tube of 7-14 FG is usually adequate although 28FG may be required with mechanical ventilation.
  • The tube is attached to a Heimlich flutter valve. Some people prefer an underwater drain so that they can see that air is being withdrawn.
  • A valve permits mobility and the patient may even go home with a valve after a period of observation. Chest x-ray is also necessary.
  • The tube is usually withdrawn after 2 or 3 days.
• A loculated lesion should not be drained by blind placement of a needle as it can cause air leak and worsen the condition. The needle should be guided by fluoroscopy.

Later management

• The patient must stop smoking to reduce the risk of recurrence.
• If there has been recurrence or the risk is considered high then prevention of further pneumothorax by pleurodesis should be considered.⁹ The procedure involves injecting a sclerosing agent between the pleura via a chest tube to cause adhesion of the surfaces. Talc is most commonly used (beware MHRA warning). ¹⁰
• For more difficult cases video-assisted thorascopic surgery (VATS) may be considered.⁹ These include resection of large bullous lesions. Pleurodesis is associated with a recurrence rate of less than 10% whilst VATS can produce an even lower figure.
• Indications for pleurodesis or VATS include persistent air leak for 7 days, recurrent or contralateral pneumothorax, bilateral pneumothorax and a high risk occupation such as diver or pilot.
• Complications include failure to prevent recurrence, acute respiratory distress, infection of the pleural space, persistent air leak and re-expansion pulmonary oedema.
• Pleurodesis certainly reduces the risk of recurrence and may be used routinely to prevent a second occurrence but it is a very painful procedure. There are no RCTs to assess the optimum timing of pleurodesis.

• Complete resolution in uncomplicated cases takes about 10 days. In the meantime the patient should not fly and should avoid remote places in case of sudden medical need.
• It is possible to stratify patients into groups with very different levels of risk of recurrence.¹¹
• Higher risk of recurrence is associated with age over 60, pulmonary fibrosis, a low ratio of weight to height and continued smoking.
• A study from near Hull found that recurrence was more common in taller men and in women. It was not related to the BMI of the patient, the initial treatment of the pneumothorax, nor to its size. Cessation of smoking reduced the risk of recurrence.¹²
• The overall risk of recurrence is that about 30% will have an ipsilateral recurrence and 10% will have a contralateral recurrence.
• The risk of fatality is greater in COPD and even greater still in AIDS (pneumothorax in AIDS tends to be a protracted and difficult condition with a markedly increased mortality). Figures of 5% and 25% respectively are quoted.
• An English study showed a death rate of 1.26 per million for men and 0.62 per million for women.³
• There is a biphasic distribution for incidence but it is the older age group where there is the greater risk of death.