Tag Archives: pneumothorax

Best of AAST #5: Pneumothorax – How Big Is Too Big?

Deciding when to place a chest tube can be challenging. Sometimes, it’s obvious: there is a large hemo- or pneumothorax staring you in the face on the chest x-ray. But sometimes, it’s there but “not that big.” The real question is, how big is too big.

That’s a question that’s been very difficult to quantify. The authors of this abstract, from the Medical College of Wisconsin, conducted a six-year retrospective review of every patient with an isolated pneumothorax at their Level I trauma center. Based on their previous research, a 35mm threshold was used to stratify patients into two groups. This measurement was obtained from axial images of a CT scan. Statistical analysis was performed to identify the predictive value in determining whether the patient could be managed without a chest tube.

Here are the factoids:

  • A total of 1767 patients had a pneumothorax during the 6-year period, and about half met inclusion criteria for the study
  • Of the 385 with pneumothorax alone, 92% were managed without a chest tube
  • Of those 353, 95% had a maximum chest wall to lung distance (335)
  • The 35mm measurement was statistically shown to be an independent predictor of successful management without a tube for both blunt and penetrating trauma

Bottom line: Not so fast! Although this looks like a slam dunk abstract, it’s really not. First, many (or most?) pneumothoraces are initially diagnosed using a plain old chest x-ray. A 35mm measurement is meaningless here because there can be significant changes in position of the pneumothorax on the image. Sometimes, the air is located anteriorly with little or no lateral component.  Does this mean we should CT every patient with a known or suspected pneumothorax? I think not.

And the second issue is the subjectivity surrounding the definition of a failure. What criteria were used when the tube was actually placed in this series. If every patient had to become symptomatic first, then I might agree. But I suspect the tubes were placed when followup imaging showed that the air was just “too big.” You can’t statistic away this kind of potential bias from subjectivity.

So what’s the answer? Unfortunately, there still isn’t one. The need for a chest tube must still be based on subjective size on a chest x-ray, physiologic status, and the patient’s ability to tolerate a given amount of lost lung function. It continues to boil down to the  assessments of each trauma professional as to “how big is too big.”

Reference: Observing pneumothoraces: the 35mm rule is safe for both blunt and penetrating chest trauma. Session XVA Paper 28, AAST 2018.

Flying Or Diving After Traumatic Pneumothorax: Part 2

Yesterday, I wrote about the accepted management of and delay in flying due to traumatic pneumothorax. I republished the post because of the very recent acceptance for publication of a paper from Oregon Health Science University in Portland. The authors specifically tried to assess timing of chest tube removal and long-distance flight, and to measure the risk of pneumothorax recurrence or other complications.

The authors performed a retrospective review of a series of military patients who had sustained chest injuries that were treated with chest tubes over a 5 year period from 2008 to 2012. After tube removal and a pneumothorax-free period of at least 24 hours (by chest x-ray), the patients were then transported by air from the military theater back to the United States.

Here are the factoids:

  • Of 517 patients screened in the military trauma registry database, only 73 were available for study after applying exclusion criteria
  • Subjects were predominantly young and male, as one would expect from the injured military population, and 74% were injured by a penetrating mechanism
  • Median time that the chest tube was in place was 4 days, and median time from tube removal to flight was 2.5 days
  • All patients had post-flight documentation available for review, but only half (37) had in-flight documentation available
  • Nearly half (40%) had positive pressure ventilation in place during the flight
  • Five patients had “in-flight medical concerns” (4 were ventilated), but none were related to the pneumothorax. The four ventilated patients had ventilator issues, the non-vented patient had “self-limited discomfort without evidence of respiratory distress.”
  • None of the subjects developed a recurrent pneumothorax, either post-flight or over the following 30 days

The authors conclude that air travel after tube removal and a 24-72 hour observation period “appears safe.”

Bottom line: Not so fast! This is yet another small, retrospective study making grand claims. The study group is a very unique population: healthy, fit young men with penetrating injury. Your average civilian trauma patient is older, less healthy, and usually has a blunt mechanism with multiple rib fractures. In-flight documentation was not available in half of the cases. And a full medical team was present on the aircraft had a problem actually occurred.

Contrast this with a civilian patient on a commercial aircraft with very limited medical equipment and expertise on board. What could go wrong? I definitely do not recommend changing our practice on these patients yet based on this one paper. Until we have better guidance (more good papers) stick to the usual wait time to ensure a safe flight for your patient.

Reference: Trauma patients are safe to fly 72 hours after tube thoracostomy removal. J Trauma, published ahead of print, May 18 2018.

Flying Or Diving After Traumatic Pneumothorax: Part 1

Today, I’m dusting off an old post on flying and diving after pneumothorax. This shows the thinking up until last year. Tomorrow, I’ll write about a new paper that suggests that we can shorten the “no-fly” time considerably.

Hint: no changes to the diving recommendations. One pneumothorax is likely to ground you forever.

Patients who have sustained a traumatic pneumothorax occasionally ask how soon they can fly in an airplane or scuba dive after they are discharged. What’s the right answer?

The basic problem has to do with Boyle’s Law (remember that from high school?). The volume of a gas varies inversely with the barometric pressure. So the lower the pressure, the larger a volume of gas becomes. Most of us hang out pretty close to sea level, so this is not an issue. But for flyers or divers, it may be.

Flying

Helicopters typically fly only one to two thousand feet above the ground, so the air pressure is about the same as standing on the earth. However, flying in a commercial airliner is different. Even though the aircraft may cruise at 30,000+ feet, the inside of the cabin remains considerably lower though not at sea level. Typically, the cabin altitude goes up to about 8,000 to 9,000 feet. Using Boyle’s law, any volume of gas (say, a pneumothorax in your chest), will increase by about a third on a commercial flight.

The physiologic effect of this increase depends upon the patient. If they are young and fit, they may never know anything is happening. But if they are elderly and/or have a limited pulmonary reserve, it may compromise enough lung function to make them symptomatic. And having a medical problem in an aluminum tube at 30,000 feet is never good.

Commercial guidelines for travel after pneumothorax range from 2-6 weeks. The Aerospace Medical Association published guidelines that state that 2-3 weeks is acceptable. The Orlando Regional Medical Center reviewed the literature and devised a practice guideline that has a single Level 2 recommendation that commercial air travel is safe 2 weeks after resolution of the pneumothorax, and that a chest x-ray should be obtained immediately prior to travel to confirm resolution.

Diving

Diving would seem to be pretty safe, right? Any pneumothorax would just shrink while the diver was at depth, then re-expand to the original size when he or she surfaces, right?

Not so fast. You are forgetting why the pneumothorax was there in the first place. The lung was injured, most likely via tearing it, penetration by something sharp, or popping a bleb. If the injured area has not completely healed, then air may begin to escape through it again. And since the air used in scuba diving is delivered under pressure, this could result in a tension pneumothorax.  This is disastrous underwater!

Most injuries leading to pneumothorax heal completely. However, if there are bone spicules stuck in the lung or more complicated parenchymal injuries from penetrating injury, they may never completely heal. This makes the diver susceptible to a tension pneumothorax anytime they use their regulator.

Bottom line: Most patients can safely travel on commercial aircraft 2 weeks after resolution of pneumothorax. Ideally, a chest xray should be obtained shortly before travel to confirm that it is gone. Helicopter travel is okay at any time, since they typically fly at 1,500 feet or less.

Divers should see a physician trained in dive medicine to evaluate their injury and imaging prior to making another dive.

Tomorrow: new info on flying after pneumothorax

References:

  • Divers Alert Network – Pneumothorax – click to download
  • Practice Guideline, Orlando Regional Medical Center. Air travel following traumatic pneumothorax. October 2009.
  • Medical Guidelines for Airline Travel, 2nd edition. Aerospace Medical Association. Aviation, Space, and Environmental Medicine 74(5) Section II Supplement, May 2003.

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.

Tomorrow: A more interesting (and complicated) case of pneumomediastinum.

Flying Or Diving After Traumatic Pneumothorax

Patients who have sustained a traumatic pneumothorax occasionally ask how soon they can fly in an airplane or scuba dive after they are discharged. What’s the right answer?

The basic problem has to do with Boyle’s Law (remember that from high school?). The volume of a gas varies inversely with the barometric pressure. So the lower the pressure, the larger a volume of gas becomes. Most of us hang out pretty close to sea level, so this is not an issue. But for flyers or divers, it may be.

Flying

Helicopters typically fly only one to two thousand feet above the ground, so the air pressure is about the same as standing on the earth. However, flying in a commercial airliner is different. Even though the aircraft may cruise at 30,000+ feet, the inside of the cabin remains considerably lower though not at sea level. Typically, the cabin altitude goes up to about 8,000 to 9,000 feet. Using Boyle’s law, any volume of gas (say, a pneumothorax in your chest), will increase by about a third on a commercial flight.

The physiologic effect of this increase depends upon the patient. If they are young and fit, they may never know anything is happening. But if they are elderly and/or have a limited pulmonary reserve, it may compromise enough lung function to make them symptomatic. And having a medical problem in an aluminum tube at 30,000 feet is never good.

Commercial guidelines for travel after pneumothorax range from 2-6 weeks. The Aerospace Medical Association published guidelines that state that 2-3 weeks is acceptable. The Orlando Regional Medical Center reviewed the literature and devised a practice guideline that has a single Level 2 recommendation that commercial air travel is safe 2 weeks after resolution of the pneumothorax, and that a chest x-ray should be obtained immediately prior to travel to confirm resolution.

Diving

Diving would seem to be pretty safe, right? Any pneumothorax would just shrink while the diver was at depth, then re-expand to the original size when he or she surfaces, right?

Not so fast. You are forgetting why the pneumothorax was there in the first place. The lung was injured, most likely via tearing it, penetration by something sharp, or popping a bleb. If the injured area has not completely healed, then air may begin to escape through it again. And since the air used in scuba diving is delivered under pressure, this could result in a tension pneumothorax.  This is disastrous underwater!

Most injuries leading to pneumothorax heal completely. However, if there are bone spicules stuck in the lung or more complicated parenchymal injuries from penetrating injury, they may never completely heal. This makes the diver susceptible to a tension pneumothorax anytime they use their regulator.

Bottom line: Most patients can safely travel on commercial aircraft 2 weeks after resolution of pneumothorax. Ideally, a chest xray should be obtained shortly before travel to confirm that it is gone. Helicopter travel is okay at any time, since they typically fly at 1,500 feet or less.

Divers should see a physician trained in dive medicine to evaluate their injury and imaging prior to making another dive.

References:

  • Divers Alert Network – Pneumothorax – click to download
  • Practice Guideline, Orlando Regional Medical Center. Air travel following traumatic pneumothorax. October 2009.
  • Medical Guidelines for Airline Travel, 2nd edition. Aerospace Medical Association. Aviation, Space, and Environmental Medicine 74(5) Section II Supplement, May 2003.