Tag Archives: pneumothorax

Yet Another Paper on Treating Pneumothorax With Oxygen?

Back in February, I thought I closed the door on using high inspired oxygen to try to speed up the resolution of pneumothorax (see related post below). I’ve just run across another attempt which is equally as bad!

This article was published in the Journal of Pediatric Surgery in 2000. The authors randomly divided 27 rabbits into three groups: room air, 40% O2, and 60% O2. Each was given a complete pneumothorax and received chest xrays twice a day. The average time to resolution was measured in each group.

At first glance, it appears that the higher O2 groups resolve faster. But wait, something’s fishy here! In the room air group, the complete pneumothorax went away on its own in 5 days. This doesn’t really happen in people. And in the 60% group, it disappeared in a day and a half! Miraculous!

Oh, and incidentally, a quarter of the rabbits died before completion of the study.

Bottom line: At first glance, these results sure look promising. However, they are rabbits, and they don’t act like people, let alone children! And the resolution times are unrealistic for humans. I still do not recommend the use of high inspired oxygen in an attempt to resolve a pneumothorax. Either some kind of tube is needed for larger volumes (small caliber if air only, bigger if blood is present), or it will go away on its own if the pneumothorax is small.

Related posts:

Reference: Zierold et al. Supplemental oxygen improves resolution of injury-induced pneumothorax. J Pediatric Surg 35(6):998-1001, 2000.

Flying After Pneumothorax

Patients who have sustained a traumatic pneumothorax occasionally ask how soon they can fly in an airplane 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.

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.

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 xray should be obtained immediately prior to travel to confirm resolution.

Bottom line: 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.

References:

  • 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.

When To Remove a Chest Tube

Chest tubes are needed occasionally to help manage chest injuries. How do you decide when they are ready for removal?

Unfortunately, the literature is not very helpful in answering this question. To come up with a uniform way of pulling them, our group looked at any existing literature and then filled in the blanks, negotiating criteria that we could all live with. We came up with the following.

Removal criteria:

  • No (or a minimal, stable) residual pneumothorax
  • No air leak
  • Less than 150cc drainage over the past 3 shifts. We do not use daily numbers, as it may delay the removal sequence. We have moved away from the “only pull tubes on the day shift” mentality. Once the criteria are met, we begin the removal sequence, even in the evening or at night.

Removal sequence:

  • Has the patient ever had an air leak? If so, they are placed on water seal for 6 hours and a followup AP or PA view chest x-ray is obtained. If no pneumothorax is seen, proceed to the next step.
  • Pull the tube. Click here to see a video demonstrating the proper technique.
  • Obtain a followup AP or PA view chest x-ray in 6 hours.
  • If no recurrent pneumothorax, send the patient home! (if appropriate)

Click here to download the full printed protocol.

How To Predict the Need for Chest Tube in Occult Pneumothorax

Occult pneumothorax occurs somewhere between 2% and 12% in all blunt trauma patients. Many of these pneumothoraces never progress and thus never need treatment. Is there a way that we can identify ones that are likely to get worse?

A retrospective study of 283 blunt trauma patients with occult pneumothorax was presented at the EAST Annual Scientific Assembly last January. A total of 98 of these patients underwent chest tube insertion within 7 days, and 185 patients were successfully observed.

The authors noted an inverse relationship between age and successful conservative management. Patients with more serious injuries failed expectant management more frequently. Finally, patients with more rib fractures also tended to fail.

The authors estimated the risk of failure of expectant management based on these critieria and found:

  • Age > 35 – 36%
  • ISS > 24 – 20%
  • Rib fractures >= 4 – 53%

The risk with having none of these was 10%, and the risk with all was 75%! 

The time interval for placement was also interesting. 80% of the failures requiring a chest tube occurred within 24 hours, with most occurring in the first 2 hours. The authors also found that 40% of patients who were placed on a ventilator failed.

Obviously, this is a small retrospective study and the exact criteria for placing a chest tube were not specified. Nevertheless, it provides a simple tool that allows us to keep an eye on a subset of patients who are likely to fail observation of occult pneumothorax.

Reference: Factors Predicting Failed Observation of Occult Pneumothoraces in Blunt Trauma. Selander, Med Univ of South Carolina. EAST 2010 Annual Scientific Assembly.

Extended FAST Exam in Trauma Patients

By now, every emergency medicine physician and surgeon knows what FAST is. This valuable technique allows us to quickly (get it?) determine whether a patient has blood in the abdomen or around the heart which might require operative management. Extended FAST (E-FAST) is an extension of the original technique that allows us to detect the presence of pneumothorax or hemothorax more quickly and accurately than with the conventional chest x-ray.

Both hemothorax and pneumothorax can be missed by x-ray. It takes at least 200cc of free fluid in the chest to show on the chest x-ray, assuming an ideal body habitus. As little as 20cc can be detected using the E-FAST. Studies have also shown that 30-50% of pneumothoraces are missed by x-ray. This diagnostic inaccuracy is due to the fact that hemothoraces settle out posteriorly and pneumothoraces anteriorly. Since the vast majority of chest x-rays in major trauma patients are taken with the patient supine to protect their spine, the bulk of the blood or air have layered out and cannot be seen well. A chest x-ray is still needed, however, to determine injury to the mediastinum and lung parenchyma.

E-FAST exam can be performed by using the standard curvilinear probe. It is usually placed longitudinally on the anterior chest to detect pneumothorax, using the space between two ribs as the “window” to the pleura. The depth setting should be adjusted so that only about 4cm is visible on the display. The junction of the visceral and parietal pleura should be visualized at the backside of the ribs. With a very steady hand, the junction between the two sets of pleura should be scrutinized closely.

If the two sets of pleura slide freely over each other, pneumothorax is unlikely. If not, it may be present. Pneumothorax is not a uniform phenomenon, except when it is of large size. It may be necessary to move the probe to a few other rib spaces to ensure that a smaller pneumothorax is not present.

FALSE POSITIVE ALERT! If the patient is not ventilating well, or if they have a right mainstem intubation, the affected lung(s) may not show the sliding sign, leading the examiner to think they have a problem when they may not.

To detect a hemothorax, the probe is directed upward somewhat when doing the right and left upper abdominal views. A dark triangle located above the diaphragm indicates fluid in the chest (blood). The dark crescent on the left in the image below is a large hemothorax.

E-FAST hemothorax

The bottom line: Extended FAST can be helpful in detecting a significant hemothorax or pneumothorax and can expedite the definitive management of those conditions. If you are already familiar with FAST, a little extra ultrasound training may be very helpful.