|Ok, that was too aggressive - dial it back next time.|
1. It's rare!
While some authors have described a 6% rate of tension PTX in prehospital trauma patients, the rate is probably far lower in most U.S. EMS systems, with some estimating it happens in fewer than 0.3% of blunt trauma patients.
Another study, published in 2013, found that about 1% of the trauma patients coming into a Level 1 center had received a needle by EMS for a suspected PTX, and that most of them ended up getting a chest tube in the ED or OR.
Problem is, they weren't able to tell if the patients had had a tension PTX when EMS needled them, or just a plain ol' pneumo. So, at worst, 1% of severe trauma patients have a tension PTX.
2. Paramedics have trouble identifying it.
That last study showed that paramedics are pretty good at diagnosing a pneumothorax. How good are they at diagnosing the tension part?
A study done in Nashiville looked at 19 patients who got a needle decompression by EMS for suspected tension. About 1/4 of those patients were proven to have any sort PTX (tension or not), and only 2/14 of the living patients were considered to have had a tension PTX (based on finding an air leak after placing a chest tube).
So, only 14% of patients who got a needle actually had a tension PTX
3. Diminished lung sounds & crepitus ≠ tension
A patient can have complete collapse of a lung, and still not need a needle!
A few months ago one of the medics was concerned that they hadn't treated a trauma patient as aggressively as he should have. The patient had fallen a few days prior, and was complaing of shortness of breath. The medic noted bruising over the chest, paradoxical chest wall motion, and absent lung sounds. Nevertheless, the patient was breathing better on 2 lpm of oxygen, and the vitals were fine.
In the ED, the patient was promptly sent to the CT scan...
|Pneumthorax, as well as subcutaneous air|
It doesn't sound like it. It's important to remember why a tension pneumo is bad. Progressive collapse of the lung leads to hypoxia, and the rise in intrapleural pressures compress the IVC, leading to hypotension. In other words, patients don't die from a pneumothorax - they die from hypoxia and shock. Rogue Medic wrote about this at some length, and you might enjoy his take on the subject.
So if subcutaneous emphysema and absent lung sounds don't require you to decompress, what signs should? A very thorough (and free!) review article from 2005 provided a list of the signs that trauma experts agree could warrant EMS attempting to decompress.
Just remember - hypoxia and hypotension!
|It's only helped in one case report.|
4. Your needle may be too short (or your patient too big...)
So, another medic brought in a trauma patient, thrown from a motorcycle, with pain over the left chest, and absent lung sounds as well. The medic had already needled the chest with the standard 14g IV catheter, but reported that lung sounds were still absent.
Sounded like a no-brainer to me; if the patient hadn't already needed a chest tube before, now they most likely did (since a needle decompression can also cause a pneumothorax). But when the patient was rolled into the trauma bay, we found no pneumo on chest x-ray, ultrasound, or even CT. Heck, looking at the CT, we realized there was no way the stubby 14 g ever made it near the lung!
This is a very common experience - unless you have a special long catheter, you may not be able to reach the pleural space, especially in the standard "midclavicular, 2nd intercostal space" that we've been taught. Why? Because we're all getting bigger, and the catheters are not!
|A standard 14g iv catheter; 2" or 5 cm,|
Seems big at first, but take a look at where we're trying to put this needle:
|People can be thick, both in the 2nd ICS anteriorly (left),|
as well as the 5th ICS laterally (right)
(Adapted from Schroeder et al)
One option is to place the needle at the 5th ICS, along the anterior axillary line, since there is generally less muscle and fat there than at the traditional 2nd ICS. One study, done in Los Angeles, found that a standard 5 cm (2 inch) needle placed at the 2nd ICS would be too short in 42% of patients, but only in 15% at the 5th ICS.
So, a lateral placement might help, but so might more needle. They make a longer 14 g iv catheter just for decompressing, extra long at 3.25 inches, or 8 cm. Of course, what's the downside of having an extra-long needle shoved into the left side of the chest?
|"With a PTX, is the blood supposed to shoot out?"|
A pneumothorax happens relatively often in severe trauma, but these do not require any specific prehospital treatment. A tension PTX, on the other hand, is rare, difficult to diagnose in the field, and there are some obstacles to treating it appropriately.
You're looking for a patient with not just absent lung sounds, but persistent hypoxia, and worsening hypotension. And when you place the catheter, you have to make sure it's actually reaching the pleura - but not too far in!