All posts by TheTraumaPro

Flying And Pneumothorax: Part 2

Some time ago, I wrote about the effect of flying on pneumothorax (PTX). It was more of a hypothetical treatise, discussing Boyle’s law and such. I also cited a practice guideline and another empiric guideline from the Aerospace Medical Association. But there was little, if any, real data to base recommendations on.

A recent study has tried to rectify this. They performed a prospective, observational study of 20 patients with traumatic pneumothorax. All were treated with either a chest tube (70%) or high flow oxygen therapy (30%) (they must not have read my many posts on the futility of this; see the links below). If a chest tube had been inserted, it had to have been removed for 4 to 48 hours before enrollment in this study, and the PTX had to be resolved to the satisfaction of the surgeon. This did not necessarily mean complete resolution.

Here are the factoids:

  • A hyperbaric chamber was used to simulated the cabin altitudes of commercial jetliners
  • 10 patients were taken up to 8400 feet, the typical cabin altitude when a jet flies at 40000 feet
  • 10 patients were taken up to 12650 feet to compensate for the fact that the altitude of the medical center conducting the study was already 4500 feet (Murray, UT). This simulated an 8400 foot altitude increase for ground dwellers in Murray.
  • Results were measured using portable chest x-ray (!??)
  • PTX etiology was 90% blunt, 10% penetrating
  • At 8400 feet, average PTX size doubled from 4.5mm to 10mm
  • At 12650 feet, average PTX size nearly tripled from 3.2 to 8.7mm. Three of 4 patients without a baseline PTX developed one at this altitude. 
  • Some patients in each group required supplemental O2 to maintain normal oxygen saturation readings

Based on these results, the authors believe that patients who had a PTX might be able to fly sooner than 2 weeks. But there are many problems with this study. First, using a chest x-ray to monitor increases in size (or judge pre-flight size) is notoriously inaccurate. Next, the statistical methods and sample size are just not adequate. And finally, the fact that PTX size increases predicted by Boyle’s law and O2 sat changes occurred is very worrisome.

Bottom line: This study was a nice try, but not robust enough to change anything. Yes, there is little data to support the 2 week no-fly rule after pneumothorax. But the size increases of the PTX in this study were worrisome, particularly because they used a diagnostic test that notoriously underestimates their size. I recommend sticking with the current recommendations and constructing a much better study.

Related posts:

Reference: Cleared for takeoff: The effects of hypobaric conditions on traumatic pneumothoraces. J Trauma 77(5):729-733, 2014.

Up In The Air: Tree Stand Injuries

Deer hunting season is upon us again, so it’s time for emergency departments to start seeing an increase in hunting injuries. Although you would think this would mean accidental gunshot wounds, that is not the case. The most common hunting injury in deer season is a fall from a tree stand.

Tree stands typically allow a hunter to perch 10 to 30 feet above the ground and wait for game to wander by. They are more frequently used in the South and Midwest, usually for deer hunting. A recent descriptive study by the Ohio State University Medical Center looked at hunting related injury patterns at two trauma centers.

Half of the patients with hunting-related injuries fell, and 92% of these were tree stand falls. 29% were gunshots. The authors found only 3% were related to alcohol, although this seem very low compared to our experience in Minnesota.

Most newer commercial tree stands are equipped with a safety harness. The problem is that many hunters do not use it. And don’t look for comparative statistics anytime soon. There are no national reporting standards.

The image on the left is a commercial tree stand. The image on the right is a do-it-yourself tree stand (not recommended). Remember: gravity always wins!

Commercial tree stand Do-it-yourself tree stand

October Newsletter Released To Subscribers Wednesday!

The October Trauma MedEd Newsletter will be released to subscribers over this Wednesday. I’ll be covering Inside Stuff. Articles include:

  • Managing foreign bodies
  • Orthopedic implants and the TSA
  • Gunshots and lead poisoning
  • And more!

Anyone on the subscriber list as of 8PM Tuesday (CST) will receive it on Wednesday, November 5. I’ll release it to everyone on Friday via the blog. So sign up for early delivery now by clicking here!

Pick up back issues here!

Ever Wonder Where The Golden Hour Came From?

Everywhere you turn in the trauma and EMS world, you run into the concept of the “golden hour.” Basically, it refers to the idea that it’s important to get an injured patient to definitive care promptly, or mortality begins to rise. It has been used to justify a lot of what we do in trauma care and trauma systems. But where did this come from? And is it true?

The BTLS course attributes the term to R Adams Cowley from the ShockTrauma Center in Baltimore. Unfortunately, no references are given. A biography of Cowley entitled Shock-Trauma names him the author of the term, basing it on dog research. No references were given.

A review of Cowley’s research reveals a few tidbits. A case series of patients implies that speed is good, but does not analyze time to definitive care. It does reference older work by other authors, but once again, no relationship between timing and outcome is evaluated.

A textbook edited by Cowley contains a reference to an article about “Cowley’s golden hour.” This article contains a statement that “patients are assumed to be dying and much of the golden hour has passed.” It goes on to state that the first 60 minutes after injury determines the patient’s mortality. It, in turn, refers to another of his earlier articles. This one states that “the first hour after injury will largely determine a critically injured person’s chance for survival." No data or reference is given.

Bottom line: The concept of the "golden hour” has taken on a life of its own. Yes, it’s a good idea. And yes, there is some actual data to support it, although the quality is somewhat lacking. But this does point out the need to question everything, even some of our most deeply held beliefs. They are not always what they seem to be.

Reference: The Golden Hour: scientific fact or medical urban legend? Acad Emerg Med 8(7):758-760, 2001.

Chest X-Ray After Chest Tube: Why Do We Do It?

More dogma, or is it actually useful? Any time a chest tube (tube thoracostomy) is inserted, we automatically order a chest x-ray. Even the ATLS course recommends obtaining an image after placement. But anything we do “automatically” is grounds for critical analysis to see if there is a valid reason for doing it. 

A South African group looked at the utility of this practice retrospectively in 1004 of their patients. They place 1042 tubes. Here are the factoids:

  • Patients were included if they had at least one chest x-ray obtained after insertion
  • Patients were grouped as follows: Group A (10%) had the tube inserted on clinical grounds with no pre-insertion x-ray (e.g. tension pneumothorax). Group B (19%) had a chest x-ray before and had ongoing clinical concerns after insertion. Group C (71%) had a chest-xray before and no ongoing concerns.
  • 75% of injuries were penetrating (75% stab, 25% GSW), 25% were blunt
  • Group A (insertion with pre-x-ray): 9% had post-insertion findings that prompted a management change (kinked, not inserted far enough)
  • Group B (ongoing clinical concerns): 58% required a management change based on the post-x-ray. 33% were subcutaneous or not inserted far enough (!!)
  • Group C (no ongoing clinical concerns): 32 of 710 (5%) required a management change, usually because the tube was too deep

The authors concluded that if there are no clinical concerns (tube functioning, no clinical symptoms) after insertion, then a chest x-ray is not necessary. 

Bottom line: But I disagree with the authors! Even with no obvious clinical concerns, the tube may not be functioning for a variety of reasons. Hopefully, this fact would then be discovered the next day when another x-ray is obtained. But this delays the usual progression toward removing the tube promptly by at least one day. It increases hospital stay, as well as the likelihood of infection or other hospital-associated complication. A chest x-ray is cheap compared to a day in the hospital, which would potentially happen in 5% of these patients. I recommend that we continue to obtain a simple one-view chest x-ray after tube insertion.

Related posts: