Q. What causes subcutaneous emphysema in a patient with a pleural chest tube with a persistent air leak? Is it treatable and what assessments should be considered in patient care?
A. Subcutaneous air, also called subcutaneous emphysema or surgical emphysema, occurs in patients with chest tubes when air leaks under enough pressure to track along the tissue planes in the deepest layer of the skin, the subcutaneous layer. This can occur at the drain site or at a different site of pleural injury.1
Air or fluid will take the path of least resistance. For patients with pneumothorax or a postoperative air leak, that is usually through the chest tube. However, there are situations in which the path through the tissue is accessible and less resistant to air flow than the route through the chest tube:
- Chest tube is too small (the smaller the tube’s diameter, the higher the resistance), particularly in relation to the size of the pleural incision
- Chest tube is occluded2
- Chest tube eyelet(s) has migrated out of the pleural space2
- Dependent loop in drainage tubing is filled with stagnant fluid3
- High ventilator pressures, particularly PEEP4
- Chest tube penetrating lung parenchyma or other errors in placement1,2,4
Two retrospective reviews have examined the association of subcutaneous air with chest drainage. In one, 18% of chest tube patients had subcutaneous air (SQ).2 Of these, 80% were patients with pneumothorax or postthoracotomy; 20% had pleural effusions. Compared with a paired cohort at 3%, 20% of SQ patients had errors in tube placement. The other study looked at a database of patients with pulmonary resection in which 6% had clinically apparent SQ.5 Patients with poor preoperative pulmonary function, air leaks, and previous thoracotomy were more likely to have SQ. The researchers discovered that patients whose SQ did not resolve with chest drain suction had postop lung adherence to the intercostal space that had been opened, causing an alveolar-subcutaneous fistula. After a 16-minute (median time) VATS procedure to resolve the adhesion, the air was redirected to the pleural space, and 98% of patients’ SQ was resolved within 24 hours.5
Case studies have been published describing clinical conditions associated with subcutaneous emphysema, including bronchial disruption from blunt chest trauma following extrication after an earthquake,6a motor vehicle crash,7 and a bicycle accident.8 It can also be the first sign of an iatrogenic pneumothorax following subclavian venous catheter4 or pacemaker1insertion.
There have also been reports of air entering the epidural space9 and vertebral artery dissection10 after subcutaneous air from pneumothorax tracked into the neck. The posterior mediastinum and neck can communicate through fascial planes, and from there, air can move into the spinal canal through the intervertebral foramen, the opening for the spinal nerve.9
While most instances of subcutaneous air relating to chest drainage are troubling cosmetically, it usually resolves without further problem.1,3 However, in rare cases, air in the neck can lead to airway obstruction, first evidenced by a change in voice.1,5 In addition, air in the tissue planes of the chest can cause a restrictive limit on respirations,1,8 similar to that seen with edema following chest wall thermal burns. The most important care is to determine why the subcutaneous leak is occurring and to correct that problem.2If the tube isn’t functioning properly, the patient could be at risk for recurrent pneumothorax and even tension pneumothorax, particularly with positive pressure ventilation.1
Nursing assessment of any patient with a chest tube should include regularly palpating the chest wall surrounding the tube. There is no routine need to remove the dressing; this palpation can be done over and around the dressing. If air accumulation is sudden and extensive, it will be easily visible. As with any evidence of a significant change, check airway, breathing and circulation first and then proceed to the drain.
Once subcutaneous air is detected, a thorough, but rapid assessment is important to determine if there is a problem with the chest drain system that can be easily fixed. Trace the tube from where it leaves the chest to the drain to ensure it is not pinched, kinked, or clamped; ensure there is no fluid in the tubing that could collect in a dependent loop.3 If suction is ordered, check the suction control chamber to make sure there is bubbling or that the suction indicator is visible in a dry control drain. If no suction is ordered, check to make sure the drain is open to atmosphere; if there is a stopcock on the suction tubing, make sure it is fully open.
If the drain is not connected to suction, the next step is usually to get an order to connect to suction and for a chest x-ray to check for pneumothorax, chest tube position, and lack of lung re-expansion.3,5,7,9 Sometimes, restarting or increasing the level of suction may solve the problem. If the patient is not on a ventilator and there are no contraindications, administering oxygen with a non-rebreather mask will facilitate resorption of nitrogen from the tissues.1
If no cause is evident, carefully remove the dressing to inspect the chest tube as it leaves the chest wall. Chest tubes have openings in the distal end to facilitate drainage. The number and position of the holes depends on the particular tube. In addition, tubes have a blue line that will show on an x-ray. The opening closest to the skin will be on the line enabling the position to be checked on a chest x-ray as a gap in the line (see arrow).2 Even if the opening isn’t visible at the incision, it may be outside the pleural space, allowing air to flow into the subcutaneous tissue. If the tube has pulled out slightly, it will have to be replaced. The tube is no longer sterile once it crosses the incision, so it cannot be pushed back into the chest.
Keep in mind that even if tube malposition didn’t cause the subcutaneous air, as air accumulates, the skin becomes “thicker” and this can cause the tube to slide out of proper position.2 If the tube doesn’t seem to be working, the physician may choose to add another tube or replace the potentially malfunctioning tube.4,9
Once the chest tube situation has been addressed, and the patient is no longer at risk, additional nursing care will need to focus on skin care. In a large majority of cases, air will be reabsorbed without sequelae. There have been some reports of incising the fascia to allow air to escape, inserting angiocatheters connected to suction into the subcutaneous space, and tissue massage, and a detailed report describes the use of a negative pressure wound therapy dressing, complete with information on integrating this dressing with chest drainage.11 The time for resolution will depend on the cause, the control of the cause, and the area affected. In the meantime, meticulous care of the distended skin and protection from friction and shear forces will reduce the risk for skin breakdown.