Tag Archives: pneumothorax

Best Of: What Percent Pneumothorax Is It?

Frequently, radiologists and trauma professionals are coerced into describing the size of a pneumothorax seen on chest xray in percentage terms. They may something like “the patient has a 30% pneumothorax.”

The truth is that one cannot estimate a 3D volume based on a 2D study like a conventional chest xray. Everyone has seen the patient who has no or a minimal pneumothorax on a supine chest xray, only to discover one of significant size with CT scan.

Very few centers have the software that can determine the percentage of chest volume taken up with air. There are only two percentages that can be determined by viewing a regular chest xray: 0% and 100%. Obviously, 0% means no visible pneumothorax, and 100% means complete collapse. Even 100% doesn’t really look like 100% because the completely collapsed lung takes up some space. See the xray at the top for a 100% pneumothorax.

If you line up 10 trauma professionals and show them a chest xray with a pneumothorax, you will get 10 different estimates of their size. And there aren’t any guidelines as to what size demands chest tube insertion and what size can be watched.

The solution is to be as quantitative as possible. Describe the pneumothorax in terms of the maximum distance the edge of the lung is from the inside of the chest wall, and which intercostal space the pneumothorax extends to. So instead of saying “the patient has a 25% pneumo,” say “the pneumothorax is 1 cm wide and extends from the apex to the fifth intercostal space on an upright film.”

Managing Chest Tube Air Leaks

There are a lot of opinions and not so much literature on how to manage chest tube air leaks. Here is some practical advice on how to deal with this occasional problem.

Most air leaks are an alveolar-pleural fistula, representing a connection between a very small airspace and the pleura. This should not be confused with a bronchopleural fistula, which involves larger airways and is much more challenging to manage.

First, identify what kind of leak it is. Remember, dry seal chest tube systems will not show an air leak unless it has a fluid chamber that can be filled with water (see related post below).

  • Expiratory – occurs during normal expiration only
  • Forced expiratory – occurs only with coughing
  • Inspiratory – occurs during inspiration in ventilated patients
  • Continuous

Inspiratory leaks are rare and should be managed conservatively with maneuvers to minimize airway pressures. Continuous air leaks can be monitored, but may indicate a bronchopleural fistula.

Expiratory and forced expiratory types account for about 98% of all air leaks. Small air leaks should be managed with water seal, not with increased suction. The main concept is to reduce air flow through the fistula so it can heal. A prospective study has shown that this technique stops small to moderate size leaks sooner than leaving on suction.

Larger air leaks will probably not seal on their own and are probably not safe to place on water seal. They will likely require pleurodesis, either chemical or mechanical via a VATS procedure. Blood and fibrin patches have also been tried.

Any air leak that extends hospital stay should be evaluated for appropriateness of discharge with a Heimlich valve or VATS pleurodesis.

References:

  • A prospective algorithm for the management of air leaks after pulmonary resection. Ann Thoracic Surg 66:1726-1731, 1998.
  • Prospective randomized trial compares suction versus water seal for air leaks. Ann Thoracic Surg 71:1613-1617, 2001.

Related posts:

Is It Really Safe To Observe Occult Pneumothorax?

Occult pneumothorax is the most common incidental finding on CT imaging, occurring in 2% to 10% of trauma patients. By definition, an occult pneumothorax is a pneumothorax that is seen only on CT and not a conventional chest x-ray. When detected, the question that comes to mind is, will this patient need a chest tube?

The AAST conducted a trial encompassing the experience at 16 Level I and II trauma centers around the US. They looked at injury severity, specific chest injuries, ventilator settings if on positive pressure ventilation (PPV) and size of pneumothorax. The size was calculated by measuring the largest air collection along a line perpendicular to the chest wall (see image above). Failure of observation meant that a thoracostomy tube was placed.

The 2 year study looked at a total of 448 occult pneumothoraces that were initially observed. Key findings of the study were:

  • Injury severity was no different between failure and non-failure groups
  • There was a 6% failure rate overall
  • PPV alone was associated with an increased failure rate of 14%
  • Surgical intervention requiring PPV was not associated with an increased failure rate
  • Pneumothorax size > 7mm, positive pressure ventilation, progression of the pneumothorax, respiratory distress and presence of hemothorax were associated with failure.
  • Pneumothorax size was not entirely reliable for predicting failure, since patients with sizes as small as 5mm on PPV and 3mm not on PPV failed in this series

Bottom line: Most blunt trauma patients with an occult pneumothorax can be safely observed. A followup chest x-ray should be obtained to look for progression. If the patient progresses, is placed on PPV, has a hemothorax or develops respiratory distress, have a low threshold for inserting a drainage tube. Maximum pneumothorax size may predict failure when large, but it can still happen with very small air collections.

Related posts:

Reference: Blunt traumatic occult pneumothorax: is observation safe? – results of a prospective, AAST multicenter study. J Trauma 70(5):1019-1025, 2011.

CT image courtesy of Journal of Trauma

Pneumothorax in Children

Last week I wrote about pneumomediastinum in children (click here to read). This week I’ll talk about a somewhat more common problem: pneumothorax. This condition is far more mysterious than in adults.

Sports related pneumothorax rarely occurs without rib fractures, which are themselves uncommon in children. The usual mechanism is barotrauma, most likely from an impact while the glottis is closed. The typical presentation is that of pleuritic chest pain, which may be followed by dyspnea. Focal chest wall tenderness is typically absent. Teenagers tend to engage in more strenuous activity and are more likely to actually sustain a rib fracture, so they may have focal tenderness over the fracture site.

Spontaneous pneumothorax in children is also uncommon. However, it is a very different entity. It may be related to blebs in the lungs, and may be more common in children who were born prematurely. The recurrence rate after successful treatment is approximately 50% (in small series). Recurrence is not predictable by looking for blebs on chest CT. The recurrence rate is significantly lower after VATS.

Bottom line: A child who complains of pleuritic chest pain, and especially dyspnea, should undergo a simple PA chest xray. If a pneumothorax is present, consider the following:

  • Insert a small chest tube or catheter if needed, the smaller the better. (I’m stilling looking for the answer to the question of how big a pneumothorax is big enough)
  • Don’t use high inspired oxygen; it doesn’t work. (Read my older blogs from 2010 – this one and this one, too)
  • Don’t get a chest CT for either the initial pneumothorax or any recurrences (too much radiation, too little utility)
  • If this is a spontaneous pneumothorax, caution the parents on the possibility of recurrence
  • If a spontaneous pneumothorax does recur, consult a pediatric surgeon to consider VATS pleurodesis
  • When can the child return to sports? There is absolutely no good literature. I recommend the usual time it takes most soft tissues to return to full tensile strength after injury (6 weeks).

References:

  • Management of primary spontaneous pneumothorax in children. Clin Pediatr, online ahead of print, April 11, 2011.
  • Sports-related pneumothorax in children. Pediatric Emergency Care 21(4): 259-260, 2005.

Related posts:

Thanks to Chris Chow MD for finding some of the literature for this post.

Pneumomediastinum After Falling Down

Finding pneumomediastinum on a chest xray or CT scan always gets one’s attention. However, seeing this condition after a simple fall from standing is very simple to evaluate and manage.

There are 3 potential sources of gas in the mediastinum after trauma:

  • Esophagus
  • Trachea
  • Smaller airways / lung parenchyma

Blunt injury to the esophagus is extremely rare, and probably nonexistent after just falling down. Likewise, a tracheal injury from falling over is unheard of. Both of these injuries are far more common with penetrating trauma.

This leaves the lung and smaller airways within it to consider. They are, by far, the most common sources of pneumomediastinum. The most common pattern is that this injury causes a small pneumothorax, which dissects into the mediastinum over time. On occasion, the leak tracks along the visceral pleura and moves directly to the mediastinum.

Management is simple: a repeat chest xray after 6 hours is needed to show non-progression of any pneumothorax, occult or obvious. This image will usually show that the mediastinal air is diminishing as well. There is no need for the patient to be kept NPO or in bed. Monitor any subjective complaints and if all progresses as expected, they can be discharged after a very brief stay.