Inadequate needle thoracostomy rate in the prehospital setting for presumed pneumothorax: an ultrasound study – Full paper

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Also posted over at Rogue Medic (now at EMS Blogs) and at Research Blogging.

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When I wrote Inadequate needle thoracostomy rate in the prehospital setting for presumed pneumothorax: an ultrasound study – abstract, I was only looking at the abstract. Now that I have seen the entire paper, I have not seen anything weaken the results of the study. There are plenty of points to discuss.

On the EMS Research Podcast Harry Mueller, Patrick Lickiss, Dr. Bill Toon, and I discuss this paper. In about half an hour, we go into the details. Here I will present the highlights. First, go listen to the podcast. Prehospital Needle Thoracostomy: EMS Research Episode4

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During the podcast, I suggested that Dr. Blaivas is a radiologist, or some other specialist in imaging medicine, as opposed to being an emergency physician. That is not correct. Dr. Blaivas is Professor of Emergency Medicine in the Department of Emergency Medicine at Northside Hospital Forsyth in Cumming, Georgia. Dr. Blaivas is also either the world’s first or second emergency ultrasound fellowship graduate. Therefore he is very well qualified to examine all aspects of emergency medicine and ultrasound.

Let’s look at the paper.

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An unstable trauma patient who is not oxygenating well or is hypotensive and has decreased breath sounds unilaterally on auscultation may be assumed by paramedics to have a PTX.² Not unreasonably, with lack of a more definite way to rule in or rule out the presence of a PTX, needle thoracostomy is opted for to relieve the tension that is assumed to be present.^[1]

Previous experience and this study lead me to the doubt this not unreasonable conclusion.

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In the prehospital setting where external noise and distractions may be overwhelming, release of air is frequently not audible.^[1]

This focus on decreased breath sounds may be one of the important factors in the misdiagnosis of tension pneumothorax.

How many medics are good at assessing lung sounds?

How many medics can tell the difference between the diminished lung sounds that are indicative of a tension pneumothorax and the diminished lung sounds that are consistent with any of the normal variations of lung sounds?

I would also change part of a sentence –

In the prehospital setting where external noise and distractions may be overwhelming, release of air is frequently not audible imaginary.

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Typically, in such critically ill patients, the chest tube is placed before review of a chest radiograph to confirm that the tension PTX has improved. The natural assumption is that regardless of whether a PTX was present, proper penetration of the chest wall would lead to a PTX even if it were not originally present.^[1]

Should any doctor be using this logic to decide to place a chest tube without assessing the patient?

Should any doctor be placing a chest tube without assessing the patient?

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However, if the needle did not penetrate the lung and no PTX was initially present, a chest tube could be avoided.^[1]

In the absence of a pneumothorax, a chest tube could should be avoided.

What justification is there for placing a chest tube in a patient with no indication for a chest tube?

Maybe the needle is in the chest because the medic has really scary IV skills. In this study, at least a quarter of the medics treating these patients (unless some are repeat offenders) have really scary needle decompression skills.

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The main outcome measure was whether a PTX was present. The secondary outcome measure was whether a PTX developed after catheter removal.^[1]

There does not appear to be any discussion of whether a pneumothorax developed after catheter removal.

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Physicians performed the ultrasound examinations during the secondary survey. Chest radiographs were obtained immediately after the ultrasound examinations. Examiners were not blinded to physical findings or on which side needle thoracostomy was performed.^[1]

blinding would have been nice, but this study seems to be more to demonstrate the concept that needle decompression may not even produce a simple pneumothorax. This can be left for a later study.

It would also be nice to follow up on the patients to find out if any showed any of the no pneumothorax patients showed any signs of pneumothorax later on, which could cast doubt on the ultrasound findings.

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A total of 57 patients were enrolled in the study over a 3-year period. Fifty-six patients had 1 needle thoracostomy performed, and 1 patient had 3 needle thoracostomy procedures on the same side for hypotension and persistent unilateral decreased breath sounds.^[1]

It should not surprise anyone that the patient with the multiple stab wounds 3 attempts at needle decompression did not have any kind of pneumothorax.

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A tension PTX is a life-threatening process that must be treated immediately either through needle thoracostomy or tube thoracostomy. Despite frequent use of chest radiography on patient arrival to emergency departments, many PTXs are initially missed.^[1]

It seems that a lot is missed.

Needles miss lungs.

Medics miss the absence of a tension pneumothoraces.

Doctors miss the presence of pneumothoraces.

If there is an important point to this, maybe it should be that we all need to improve our assessment for pneumothoraces and be more conservative in our treatment in the absence of unmistakable signs of a tension pneumothorax.

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The combination of unilateral decreased or absent breath sounds with instability is justifiably interpreted as the presence of a PTX. There is no way to verify or refute such a finding.^[1]

Maybe.

Maybe not.

Should we assume that a tension pneumothorax is subtle?

I don’t think so.

Why do we teach about tension pneumothorax as if it is the same as an easily missed simple pneumothorax?

I think it is because we don’t realize just how unsubtle a tension pneumothorax is.

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This study had several limitations. The first was the small sample size. Second, the sonologists were not blinded to the side on which needle decompression was attempted. Third, it is possible that some patients did in fact have a PTX that was completely relieved by needle decompression, and no more air leaked after catheter removal. Thus, the CT scan would not show even a trace PTX. Although this is possible, it is clinically very unlikely.^[1]

There are limitations, but are these results consistent with what we know about the shortcomings of EMS education and understanding of infrequently done procedures?

Absolutely.

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Click on the image to make it larger.

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From this study we cannot tell if the number that should be in the place of the double question marks is 42. Maybe it is 32. Maybe it is 22. Maybe it is 12. Maybe it is 2. Maybe it is zero. We don’t know and this study cannot tell us, which is not a fault of the study.

The same problem exists for trying to figure out the number that should be in the place of the single question mark.

We know that of the patients treated for claimed tension pneumothorax, 26% were treated by paramedics so poorly that the needle never even made it to the lung.

Should we assume that all of the patients treated with needles that actually reached the lung did have tension pneumothoraces?

There is nothing in this paper to suggest that.

There is no good reason to assume that all of the medics who missed the diagnosis also missed the lung. 26% missed the lung and missed the diagnosis.

It is reasonable to assume that some of the medics missed the diagnosis, but used a long enough needle to hit the lung. What we do not know is how many of those who hit the lung with a needle missed the diagnosis.

Another possibility is that the patient had a pneumothorax, most likely a simple pneumothorax, and the medic missed the lung with the needle, but since it was not a tension pneumothorax there was no dramatic deterioration of the patient. The needle decompression would be no more indicated for these patients than for those without any pneumothorax.

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Also covered at EMS Research Podcast Episode 4 at 510Medic.

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Footnotes:

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^[1] Inadequate needle thoracostomy rate in the prehospital setting for presumed pneumothorax: an ultrasound study.
Blaivas M.
J Ultrasound Med. 2010 Sep;29(9):1285-9.
PMID: 20733183 [PubMed - in process]

Free Full Text from J Ultrasound Med.

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Blaivas M (2010). Inadequate needle thoracostomy rate in the prehospital setting for presumed pneumothorax: an ultrasound study. Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine, 29 (9), 1285-9 PMID: 20733183

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