Atelectasis (collapsed lung tissue): causes, symptoms and treatment

The MSD Manual describes atelectasis as the collapse of lung tissue with loss of volume. The tiny air spaces of the lung (alveoli) have a natural tendency to collapse, which is countered by surfactant (which maintains low surface tension), continuous breathing, intermittent deep breathing (which releases surfactant into the alveoli) and periodic coughing (which clears secretions from the airways).

When those protective factors fail, part of the lung can lose air. The MSD Manual says the major consequences of atelectasis include impaired gas exchange (low oxygen and/or high carbon dioxide), pneumonia, and respiratory failure in severe cases. It is different from a pneumothorax, where air escapes from the lung into the space around it; the MSD Manual lists a large pleural effusion or pneumothorax as one way the lung itself can be compressed and collapse.

The MSD Manual says atelectasis itself is asymptomatic unless hypoxaemia or pneumonia develops. Symptoms of low oxygen tend to relate to how quickly the collapse came on and how much lung is involved. With rapid, extensive atelectasis, breathlessness or even respiratory failure can develop. With slowly developing, less extensive atelectasis, symptoms may be mild or absent.

Pneumonia that develops may cause cough, breathlessness and pleuritic pain (chest pain on breathing in). Pleuritic pain may also be due to the disorder that caused the atelectasis in the first place, such as chest trauma or surgery. The MSD Manual says signs are often absent if the atelectasis is minimal, and that it is often discovered incidentally on chest imaging.

• Often no symptoms when the area is small

• Breathlessness if a large area is involved or it comes on quickly

• Low oxygen levels (hypoxaemia)

• Chest pain on breathing in (pleuritic pain)

• Cough and breathlessness if pneumonia develops

The MSD Manual lists the most common factors as obstruction of the airways from the inside (for example by a foreign body, tumour or mucus plug), compression of the airways from the outside (for example by tumours or enlarged lymph nodes), suppression of breathing or cough (for example by general anaesthesia, oversedation or pain), lying flat on the back, particularly in people with obesity or an enlarged heart, and compression or collapse of lung tissue by a large pleural effusion or pneumothorax.

It says thoracic and abdominal surgeries are very common causes because they involve general anaesthesia, opioid use (with possible secondary respiratory depression) and often painful breathing, and that a malpositioned breathing tube can cause atelectasis by blocking a main bronchus. Less common causes include surfactant deficiency or dysfunction, scarring of the lung tissue, or tumours.

The MSD Manual says atelectasis should be suspected in anyone who has unexplained breathing symptoms and risk factors, particularly recent major surgery. Diagnosis is by chest radiograph (X-ray) or, particularly in milder disease, chest CT. Clinically significant atelectasis is generally visible on a chest X-ray, with findings including localised opacification of the lung and loss of lung volume, while milder cases may only be seen on CT.

If the cause is not clinically apparent, for example if it is not recent surgery, or another disorder such as a pulmonary embolism or tumour is suspected, other tests such as bronchoscopy (a camera passed into the airways) or chest CT may be necessary. Signs on examination, such as reduced breath sounds over the affected area, are detectable only if the area is large.

The MSD Manual says evidence for the efficacy of most treatments for atelectasis is weak. Nonetheless, commonly recommended measures include chest physiotherapy to help maintain ventilation and clearance of secretions, and encouragement of lung expansion techniques such as directed cough, deep breathing exercises and frequent use of an incentive spirometer, which is usually done in inpatient settings. In people who can walk, exercise such as walking is a desirable way to promote deep breathing.

Most importantly, the MSD Manual says, the underlying cause (for example a mucus plug, foreign body, tumour or pleural effusion) should be treated. For persistent mucus plugging, nebulised treatments to loosen mucus are sometimes tried, and if other measures are ineffective or an obstruction other than mucus is suspected, bronchoscopy should be performed. It also says avoiding oversedation helps ensure sufficient deep breathing and coughing, and that pain relief is needed because severe pain on breathing can stop deep breaths and coughing.

An NHS trust physiotherapy leaflet says that after surgery it is very important to complete regular deep breathing exercises as advised by your physiotherapist, because you are at higher risk of developing a chest infection. It explains that breathing deeply allows air to pass through all areas of the lungs and helps move sputum up and out, and that after surgery breathing deeply may be difficult due to pain.

The leaflet describes the cycle of breathing technique: breathing control (slow deep breaths in through the nose and out through the mouth, 5 times), thoracic expansion exercises (deep breaths in through the nose to fill the lungs, with a sniff at the end, 5 times), and, if you have sputum, a huff followed by a supported cough. It suggests hugging a pillow or rolled-up towel around the painful area when coughing. It also says that if you have problems taking slow deep breaths, staff may recommend an incentive spirometer, with 5 breaths once per hour.

The leaflet stresses getting out of bed as early as medically possible after surgery, because this allows the lungs to fully expand with air, and that remaining in bed for long periods increases the risk of complications. It adds that it is normal after abdominal surgery for the exercises to be uncomfortable, and to speak to the nursing staff so that pain is managed well enough to complete them.

• Do the breathing exercises as your physiotherapist advises, usually while sitting upright.

• Support your wound with a pillow or rolled towel when coughing.

• Ask for pain relief so you can breathe deeply and cough.

• Get out of bed as soon as your team says it is safe.

The sources read do not set out specific thresholds for atelectasis, so general principles apply. After surgery, tell the nursing or physiotherapy team if you are struggling to breathe deeply or cough because of pain, because the NHS trust leaflet says pain needs to be well managed to complete the exercises.

If you are at home and develop new or worsening breathlessness, chest pain on breathing or a cough with fever, contact your GP or NHS 111, and call 999 if you are struggling to breathe, because the MSD Manual notes that rapid, extensive atelectasis can cause breathlessness or respiratory failure and that pneumonia can follow.

Atelectasis is most often identified in hospital, after an operation or during an illness, where physiotherapists and nurses guide the breathing exercises. In other cases it may be found on a chest X-ray or CT arranged by a GP or specialist for breathing symptoms.

If you are considering private care, ask which team will investigate the underlying cause, such as an airway blockage, and who will follow up your imaging, since the MSD Manual says treating the underlying cause is the most important step.