Unlike most other body cavities the thorax is a near-rigid box which has limited ability to contract. The lung on the other hand has remarkable abilities to fill that space and seal off any leaks and pathology, almost rivalling the omentum in the abdomen, provided it is not trapped or restricted by the underlying pathology. However, failure of the lung to re-expand and fill that space leaves the patient not only debilitated with decreased respiratory function but with chronic sepsis. Much of the skill of Thoracic Surgery is in the avoidance and treatment of air space problems.

Causes

While the causes of persistent air spaces are many, the majority in the western world are iatrogenic. Persistent air leaks after lung surgery, oesophageal leaks after endoscopy or resection and complications of treatment of other intra-thoracic malignancies would be the commonest. Inadequate treatment of pleural conditions, such as effusion, haemothorax or pneumothorax, inappropriate aspiration, sub-optimal drainage are the familiar reasons for referral of these patients whose "lung didn't come up despite a number of drains…" In other parts of the world, tuberculosis is the main cause of pleural space problems. While this has in the past meant the developing countries, there is a resurgence in the developed world and old techniques are having to be re-learnt and refined.

Prevention

Many of the routine techniques we employ in pulmonary surgery are aimed at preventing air spaces. It is important to remember that what we regard as the "common" underwater seal chest drain was a revolution which actually allowed the development of Thoracic Surgery. Previously a lung which had a natural tendency to collapse inside its rigid box prevented surgeons performing lung surgery. The accurate placement, fixation and management of chest drains remains our prime defence against air spaces problems. Other means of reducing the size of redundant space such as muscle flaps, omentum, thoracoplasty or pneumo-peritoneum are secondary measures.

There are certain patients in whom a persistent air space can be predicted and in whom special techniques may need to be employed. The prime example is the patient on steroids, be it for chronic lung disease, arthritis or other chronic inflammatory disease. Not only has this patient underlying lung pathology which makes persistent air leak likely, but the ability to heal is impaired. As the immune system is impaired both bacterial and fungal pathogens are more likely to infect spaces further complicating the situation.

Most air troublesome air spaces are associated with a persistent air leak. After lung surgery the aim is to seal all air leaks. Many new glues and sealants are now available at not inconsiderable expense. The difficulty is often deciding what is practicable as the lung has an excellent ability to seal if it can be maintained in contact with the chest wall. Buttressing suture lines will assist sealing air leaks and again, while new technology has opened up new opportunities, the natural tissues available to hand include pleura, pericardium and even bulla wall. In the presence of potentially non-viable tissue, sepsis, radiation or exposed bronchial stumps, healthy tissue, be it pleura, pericardium, omentum or muscle flap, can be used as prophylaxis or treatment of an air space.

Treatments

The treatment depends on the size and location of the space, the local consequences of that space, the systemic disturbance and the patient's fitness to undergo the appropriate surgery. Some spaces need no treatment. A small loculated space which is not contaminated may seal itself. Some eventually will fill with fluid and fibrin and contract spontaneously.

Drainage

For most, the treatment of the space is drainage with appropriate treatment of the underlying condition. Adequate drainage of effusions, haemothoraces, early empyemas or pneumothoraces will usually lead to resolution. Generally, standard chest drains will suffice but heavily loculated collections or those in which access is blocked by the scapula may be better drained with cannulae placed under radiological control. Such small cannulae do seem to drain better when flushed with a fibrinolytic agent though the evidence that they actually break down loculations is scanty.

Treatment of underlying condition

Where there is a chronic infective condition such as lung abscess or tuberculosis, the pleural space problem is unlikely to resolve till appropriate systemic therapy has the underlying process under control. In tuberculosis even a badly loculated effusion with serious lung trapping may resolve with anti-tuberculous therapy.

When persistent air leak is the cause, sealing the lung becomes the major issue. Some tissue sealants such as fibrin glue can be administered via the chest drains. Whether they work by actually sealing air leaks or just by blocking the drains is a point for debate. Talc instilled as a slurry serves a similar purpose with equal success and often at less expense. The insertion of such foreign material results in surprisingly few infective complications. Surgical ligation, stapling or excision of bullae or blebs is obviously the treatment when spontaneous pneumothorax is the cause but may not be an option in the elderly emphysematous patient.

Failure of the lung to re-expand despite adequate treatment of the underlying condition.

Operative treatment of air leaks

Re-operation purely to seal air leaks doesn’t usually have much to offer unless there has been poor drain placement, failure of fixation or early removal of drains placed at surgery. While identifying and oversewing air leaks with appropriate buttresses and sealants sounds like a reasonable proposition, it is usually at the expense of creating further leaks while breaking down adhesions.

Decortication

Surgery does have a role where CT shows potentially re-expansible lung trapped by a cortex. The backbone of treatment is decortication. Decortication may be performed in the early situation with a thoracoscope but when established fibrosis is present thoracotomy and formal decortication will be needed. Further procedures such as thoracoplasty or muscle transposition may be required to fill residual space.

Muscle flap transposition

Transposing muscle serves a number of purposes including bringing viable, vascularised tissue to an area of relative ischaemia (e.g. following radiation or in the presence of chronic infection), sealing off broncho-pleural fistulae and using the bulk of the muscle to physically fill space. While a number of muscles including pectoral, latissimus, serratus and rectus abdominis, along with omentum can fill considerable space, muscle flaps are usually used in conjunction with thoracoplasty or a Claggett procedure.

Thoracoplasty

Thoracoplasty, the removal of ribs to allow the rigid box-like structure that is the thorax to collapse, was the mainstay of surgical treatment of chronic tuberculous pleural complications. There is a resurgence in the need for radical surgery now that resistant organisms are developing. The technique is useful in conjunction with decortication and muscle flap transposition for resistant air space problems.

Medium term drainage

I refer to medium term drainage as any period from approximately 5 postoperative days to 12 weeks to distinguish it from both normal postoperative drainage and long-term pleural fenestration. Medium term drainage with an appropriate valved drainage system will allow the lung to gradually fill the space as long as the lung does not have too thick a rind on it and there are no ongoing factors preventing lung re-expansion. The type of drainage system will vary with local preference though underwater seals are impractical for outpatient use. Our own preference is for a modification of the Heimlich valve – the Portex portable drainage bag (Portex, Hythe, Kent, UK). This device has a PVC flutter valve incorporated inside a drainage bag. A protected exhaust aperture prevents obstruction of outflow. The device can be worn under clothes and has been used for periods of 12 weeks or longer. In a randomised trial it was shown to provide safe, effective postoperative, inpatient chest drainage in patients not requiring suction (Graham AN, Cosgrove AP, Gibbons JR, McGuigan JA. Randomised clinical trial of chest drainage systems. Thorax. 1992 Jun;47(6):461-2). More recently, a randomised trial, comparing outpatient treatment using the Portex bag with inpatient underwater seal drainage, has shown it to be safe, effective and cost-effective in patients with persistent air leak (McManus KG, Spence GM, McGuigan JA. Outpatient chest tubes. Ann Thorac Surg. 1998 Jul;66(1):299-300)

Patient unfit for major procedure

Long-term drainage

Decortication, thoracoplasty and muscle flap transposition are major procedures and while some of these have been described under local anaesthetic, they are too drastic for many elderly, debilitated patients. In this situation a form of long-term drainage is required after the acute sepsis is brought under control by standard chest drainage. A pleural window fashioned in the most dependent part of the cavity will allow control of the sepsis but the compromise leaves a collapsed lung with little function.

Summary

Inability of the lung to re-expand leaving a chronic air space was the problem which prevented lung surgery developing till the early 20th century. As most air space problems are iatrogenic prevention is the best approach. Many of our standard routines at the end of a thoracic operation are designed to prevent such problems and attention to detail before closure of the chest will avert many complications. Most intrapleural will resolve with appropriate drainage and treatment of the underlying condition. When an air space has become established medium term drainage as an outpatient will allow a further number to resolve satisfactorily. Decortication, muscle or omental transposition and thoracoplasty are reserved for resistant cases, particularly where the underlying condition can not be fully treated. In unfit patients the surgeon may need to resort to long-term open drainage by pleural fenestration.