Tag Archives: pneumothorax

Abstracts, Thorax

Best Of AAST 2021: Chest Tube Based On Pneumothorax Size

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How big is too big? That has been the question for a long time as it applies to pneumothorax and chest tubes. For many, it is a math problem that takes into account the appearance on chest x-ray, the physiology of the patient, and their ability to tolerate the pneumothorax based on any pre-existing medical conditions.

The group at Froedtert in Milwaukee has been trying to make this decision a bit more objective. They introduced the concept of CT based size measurement using a 35mm threshold at this very meeting three years ago. Read my review here. My criticisms at the time centered around the need to get a CT scan for diagnosis and their subjective definition of a failure requiring chest tube insertion. The abstract never did make it to publication.

The authors are back now with a follow-on study. This time, they made a rule that any pneumothorax less than 35mm from the chest wall would be observed without tube placement. The performed a retrospective review of their experience and divided it into two time periods: 2015-2016, before the new rule, and 2018-2019, after the new rule. They excluded any chest tubes inserted before the scan was performed, those that included a sizable hemothorax, and patients placed on a ventilator or who died.

Here are the factoids:

  • There were 93 patients in the early period and 154 in the later period
  • Chest tube use significantly declined from 20% to 10% between the two periods
  • Compliance with the rule significantly increased from 82% to 92%
  • There was no difference in length of stay, complications, or death
  • Observation failure was marginally less in the later period, and statistical significance depends on what method you use to calculate it
  • Patients in the later group were 2x more likely to be observed (by regression analysis)

The authors concluded that the 35mm rule resulted in a two-fold increase in observation and decreased the number of unnecessary CT scans.

Bottom line: I still have a few issues with this series of abstracts. First, decision to insert a chest tube requires a CT scan in a patient with a pneumothorax. This seems like extra radiation for patients who may not otherwise fit any of the usual blunt imaging criteria. And, like their 2018 abstract, there is no objective criteria for failure requiring tube insertion. So the number of insertions can potentially be quite subjective based on the whims of the individual surgeon.

What this abstract really shows is that compliance with the new rule increased, and there were no obvious complications from its use. The other numbers (chest tube insertions, observation failure) are just too subjective to learn much from.

Here are my questions for the presenter and authors:

  • Why was there such a large increase in the number of subjects for two identical-length time periods? Both were two years long, yet there were two-thirds more patients in the later period. Did your trauma center volumes go up that much? If not, could this represent some sort of selection bias that might change your numbers?
  • You concluded that your new rule decreased the number of “unnecessary” CT scans? How so? It looks like you are using more of them!
  • Do you routinely get a chest CT on all your patients with pneumothorax? Seems like a lot of radiation just to decide whether or not to put a tube in.
  • How do you manage a pneumothorax found on chest x-ray? Must they get a CT? Or are you willing to watch them and follow with serial x-rays?
  • How do you decide to take out the chest tube? Hopefully not another scan!

There should be some very interesting discussion of this abstract!

Reference: THE 35-MM RULE TO GUIDE PNEUMOTHORAX MANAGEMENT: INCREASES APPROPRIATE OBSERVATION AND DECREASES UNNECESARY CHEST TUBES. AAST 2021, Oral abstract #56.

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Flash Pulmonary Edema After Chest Tube Insertion

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You are seeing a young man in the emergency department who gives a history of falling two days ago. He experienced chest pain at the time which has persisted, but he did not immediately seek medical care. He has noticed that he now gets winded when walking quickly or climbing stairs, and describes pleuritic chest pain.

He presents to your emergency room and on exam has a bruise over his left lateral chest wall. Subcutaneous emphysema is present, and breath sounds are absent. Chest x-ray shows a complete pneumothorax on the left.

You carefully prepare and insert a chest tube in the usual position. A significant rush of air occurs, which tapers off over 15 seconds. Here is the followup image:

About 10 minutes later you are called to his room because he is complaining of dyspnea and his oxygen saturation has decreased to 86%. Breath sounds are somewhat decreased and the tube appears to be functioning properly. You immediately obtain another chest x-ray:

What just happened? This is a classic case of unilateral “flash” pulmonary edema after draining the chest cavity. This phenomenon was first described in 1853 in a patient who had just undergone thoracentesis. It is very uncommon, but seems to occur after rapid drainage of air or fluid from the chest cavity.

Here are some interesting factoids from case reports:

  • It occurs more often in young men
  • It is most common when draining large hemo- or pneumothoraces
  • Rapid drainage seems to increase the incidence
  • It is likely due to increased pulmonary capillary permeability from inflammatory mediators or changes in surfactant
  • Symptoms typically develop within an hour after drainage

What should you do? First, if you are draining a large collection of air or blood, do it slowly. Clamp the back end of the chest tube prior to insertion (you should always do this if you value your shoes) and use it to meter the amount of fluid or air released. I typically let out about 300cc of fluid, then wait a minute and repeat until all the blood has been drained. For air, vent it for 10 seconds, then wait a minute and repeat.

In patients at high risk for this condition, apply pulse oximetry and follow for about an hour. If they still look and feel great, nothing more need be done.

References:

  • Fulminant Unilateral Pulmonary Edema After Insertion of a Chest Tube. Dtsch Arztebl Int 105(50):878-881, 2008.
  • Reexpansion pulmonary edema after chest drainage for pneumothorax: A case report and literature overview. Respir Med Case Rep 14:10-12, 2015.
  • Re-expansion pulmonary edema following thoracentesis, Can Med Assn J 182(18):2000-2002, 2010.
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Best of AAST #5: Pneumothorax – How Big Is Too Big?

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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.

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Flying Or Diving After Traumatic Pneumothorax: Part 2

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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.

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Flying Or Diving After Traumatic Pneumothorax: Part 1

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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.