A dangerous complication of thoracocentesis

Short answer

The fluid at the underwater seal should oscillate and bubble.

Long answer

After insertion of an intercostal chest drain, the drain should be connected to a drainage system containing a valve mechanism.1 In most cases this will be a bottle with an underwater seal that allows fluid or air to escape, but not enter, the pleural cavity. During inspiration the pressure in the pleural cavity falls, causing an upward movement of fluid (towards the pleural cavity) at the underwater seal. During expiration, the pressure in the pleural cavity rises, which causes downward movement of the fluid. This up and down movement of the fluid at the underwater seal is called oscillation (or “swinging”), and it confirms that the drain is in the pleural cavity and connected to the bottle within a closed system. Oscillation is therefore seen in correctly functioning drains regardless of the indication for insertion. If the fluid at the underwater seal does not oscillate, the drain is clamped or blocked, has become displaced from the pleural cavity, or is no longer operating within a closed system (for example, there is a leak in the drain or bottle connectors).

As well as preventing fluid or air from entering the pleural cavity, the underwater seal is useful for monitoring purposes. In pneumothoraxes, bubbling at the site of the underwater seal indicates that air is leaving the pleural cavity. Therefore, in a correctly functioning drain inserted for treatment of a pneumothorax, the fluid at the underwater seal should oscillate and bubble. When the pneumothorax has fully resolved, assuming there is no ongoing air leak, the fluid at the underwater seal will continue to oscillate and cease to bubble.

Short answer

Yes. The left lung has fully reinflated, suggesting that the drain is functioning correctly.

Long answer

In this case, a chest drain was inserted to treat a large left pneumothorax (fig 1). The radiograph taken one hour after chest drain insertion (fig 2) shows a fully re-expanded left lung, with no areas where lung markings are absent and no line representing the edge of a partially collapsed lung. The chest drain enters the left lateral chest wall and travels inferiorly. It should not be confused with an electrocardiograph lead, which crosses the mediastinum and right upper quadrant of the abdomen. The chest drain is difficult to see because of widespread airspace opacification of the left lung. The tip of the drain lies in front of the left hemidiaphragm. It should be remembered that the diaphragm is a three dimensional structure but chest radiographs give only a two dimensional view. There is lung tissue and surrounding pleura anterior and posterior to the diaphragm, and this is where the drain lies in this case. Although chest drains for pneumothoraxes should ideally point apically, the full re-expansion of the left lung suggests that the drain is functioning correctly, and reinsertion or repositioning of the drain is not indicated.1

Short answer

The re-expanded left lung shows widespread airspace opacification. In this clinical context, this signifies re-expansion pulmonary oedema.

Long answer

Re-expansion pulmonary oedema (REPO) is a recognised complication of drainage of pleural effusions and pneumothoraxes. Most studies show that severe REPO occurs after thoracocentesis in 0-1% of cases.2 REPO has a wide spectrum of severity, ranging from asymptomatic radiological changes to cough or mild breathlessness, through to severe chest pain, massive sputum production, hypoxia, hypotension, and even death.3 Symptoms usually occur in the first one to two hours after thoracocentesis.4

REPO is caused by hypoxia and subsequent rapid re-expansion of the collapsed lung, which results in the release of various inflammatory mediators.5 This leads to increased permeability of the alveolar-capillary membrane and the rapid passage of fluid into the alveoli. The diagnosis is made on the basis of the clinical picture and chest radiography, which shows unilateral airspace opacification of the re-expanded lung (fig 2).6

REPO is more common in young patients, those with large pneumothoraxes or in whom a large volume (>3 L) of pleural fluid is removed, and those with a longer duration of lung collapse before thoracocentesis.2 Controlled drainage of large pleural effusions by clamping the drain if more than 1.5 L of fluid is drained in the first hour after insertion, or if the patient develops a cough, may reduce the risk.1

REPO can be difficult to prevent when treating pneumothorax. Bubbling chest drains should never be clamped because this risks the development of a tension pneumothorax. As such, it is not possible to control the speed of lung re-expansion in pneumothoraxes, and rapid re-expansion may occur. The early use of suction in the treatment of pneumothorax after chest drain insertion is not routinely recommended because it will probably increase the speed of lung re-expansion and therefore the likelihood of REPO occurring.1

The diagnosis of REPO is usually clear in the relevant clinical context. The differential diagnosis of unilateral airspace opacification after chest drain insertion includes infection of the re-expanded lung, although this would be expected to develop at a later stage after lung re-expansion. Purulent sputum is usually produced in infection, whereas in REPO large volumes of frothy clear proteinaceous sputum are often seen (fig 3⇓).7 This contrasts with the frothy white-pink sputum seen in cardiogenic pulmonary oedema.

Fig 3 Frothy clear proteinaceous sputum characteristic of re-expansion pulmonary oedema

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Short answer

Management is supportive. This may include supplemental oxygen, analgesia, diuretics, continuous positive airways pressure, or invasive ventilation in severe cases.

Long answer

REPO is a difficult condition to treat, and management is supportive. Patients may develop severe chest pain, which may require strong opiate analgesia. If hypoxia occurs, oxygen should be titrated to keep oxygen saturations between 94% and 98% for most patients and 88% to 92% in those at risk of hypercapnic respiratory failure (such as certain patients with chronic respiratory conditions).8 In some cases, continuous positive airways pressure or intubation and invasive ventilation may be needed.9

The role of diuretics is controversial. In cardiogenic pulmonary oedema, increased hydrostatic pressure causes fluid to gather in the alveoli. Diuretics reduce this hydrostatic pressure, allowing fluid to move back from the alveoli into the vascular space. In REPO, it is thought that fluid is extravasated into the alveoli mainly because of increased alveolar-capillary membrane permeability, rather than increased hydrostatic pressure. This may lead to a state of hypovolaemia, where diuretics would be detrimental.10 However, others argue that the “flooding” of the lung vasculature after rapid lung re-expansion does cause an increase in hydrostatic pressure,10 and there are reported cases of successful treatment of REPO with diuretics. As a result, some support cautious administration of diuretics if there are no contraindications, such as hypotension.10

Short answer

After a pneumothorax, advise patients to return if symptoms recur, to avoid flying in the short term, and to avoid diving for life.

Long answer

After a spontaneous pneumothorax, patients should be advised to return if symptoms recur because this could indicate recurrence of the pneumothorax. Diving should be discouraged for life because of the risk of recurrence, unless a definitive procedure such as a surgical pleurectomy is performed and subsequent investigations are satisfactory.1

Advice on flying is less clear cut.1 Patients with a pneumothorax that has not fully resolved should be advised to avoid air travel because the low atmospheric pressure may lead to expansion and a tension pneumothorax. After full resolution of a pneumothorax there is no clear evidence that flying increases the risk of recurrence, but if recurrence occurs during air travel the consequences may be serious.1 Some airlines arbitrarily suggest avoiding air travel for six weeks.1 The risk of recurrence falls significantly after one year,1 so some patients may prefer to avoid air travel for a more prolonged period.

In addition, smoking increases the risk of recurrence, so patients should be encouraged to quit.1 Physical exertion has not been linked to recurrence and may resume once symptoms have resolved.