Tension pneumo treatment and chest wall thickness

November 18, 2011 by  
Filed under All Updates, EMS, Resus, Trauma, Ultrasound

An interesting ultrasound-based study challenges the assertion that a significant proportion of adults have a chest wall that is too thick for a standard iv cannula to reach the pleural space when attempting to decompress a tension pneumothorax. Perhaps there are other factors that make this technique so frequently ineffective.

The authors postulate that ultrasound measurements of chest wall thickness might be less than those obtained by CT scan due to the downward pressure on the tissues caused when the ultrasound transducer is placed on the chest, something that may also occur when a cannula is being pushed in, but would not be maintained after insertion of a cannula, perhaps leading to subsequent misplacement as the tissues recoil.

My view is that needle decompression might buy you time as a holding measure, but the patient with a tension pneumothorax will need a thoracostomy sooner rather than later.


Objective: Computed tomography measurements of chest wall thickness (CWT) suggest that standard- length angiocatheters (4.5 cm) may fail to decompress tension pneumothoraces. We used an alternative modality, ultrasound, to measure CWT. We correlated CWT with body mass index (BMI) and used national data to estimate the percentage of patients with CWT greater than 4.5 cm.

Methods: This was an observational, cross-sectional study of a convenience sample. We recorded standing height, weight, and sex. We measured CWT with ultrasound at the second intercostal space, midclavicular line and at the fourth intercostal space, midaxillary line on supine subjects. We correlated BMI (weight [in kilograms]/height2 [in square meters]) with CWT using linear regression. 95% Confidence intervals (CIs) assessed statistical significance. National Health and Nutrition Examination Survey results for 2007-2008 were combined to estimate national BMI adult measurements.

Results: Of 51 subjects, 33 (65%) were male and 18 (35%) were female. Mean anterior CWT (male, 2.1 cm; CI, 1.9-2.3; female, 2.3 cm; CI, 1.7-2.7), lateral CWT (male, 2.4 cm; CI, 2.1-2.6; female, 2.5 cm; CI 2.0-2.9), and BMI (male, 27.7; CI, 26.1-29.3; female, 30.0; CI, 25.8-34.2) did not differ by sex. Lateral CWT was greater than anterior CWT (0.2 cm; CI, 0.1-0.4; P <.01). Only one subject with a BMI of 48.2 had a CWT that exceeded 4.5 cm. Using national BMI estimates, less than 1% of the US population would be expected to have CWT greater than 4.5 cm.

Conclusions: Ultrasound measurements suggest that most patients will have CWT less than 4.5 cm and that CWT may not be the source of the high failure rate of needle decompression in tension pneumothorax.

Ultrasound determination of chest wall thickness: implications for needle thoracostomy

Am J Emerg Med. 2011 Nov;29(9):1173-7

Comments

7 Responses to “Tension pneumo treatment and chest wall thickness”

  1. Matthew Oliver on November 18th, 2011 05:44

    This is an interesting study and adds to the confusion of where to place a needle and whether it is going to do anything at all. Two other studies both released in the last few weeks both have conflicting results

    http://www.ncbi.nlm.nih.gov/pubmed/21951681

    and

    http://www.ncbi.nlm.nih.gov/pubmed/22071914

    Although, the latter study was on cadaver’s so difficult to extrapolate to a living patient.

  2. Cliff on November 18th, 2011 18:08

    Thanks for highlighting those Matthew. Can you please email me at mail@resus.me as I have some questions for you.

    Cheers

    Cliff

  3. Minh Le Cong on November 18th, 2011 21:01

    Hi Cliff
    hypothetical based on many real cases

    You are out on a remote retrieval to pick up someone who might have a pneumothorax, says after coming off a motorbike. He seems stable with perhaps some reduced air entry on one side of the chest. You have no xray, no USS.

    Would you insert an ICC prophylactic style? Or do you consider it reasonable to fly them sea level cabin pressure..say you can do that… with preparations to do a needle or open decompression emergently if need be.

    what do you think?

  4. Cliff on November 18th, 2011 22:00

    Sea level cabin with a long needle handy if otherwise completely stable.
    WTF was I doing there without ultrasound?!

  5. Tim Leeuwenburg on November 19th, 2011 18:10

    Assuming the USS probe has been damaged!

    Bugger that, with a good mechanism and reduced AE, I’d bung in a chest tube even if haemodynamically uncompromised. Better that than have to decompress a tPTX at altitude or have to convert to formal ICC in aircraft, negotiating restraints, arms, aircraft fuselage etc.

    So, if I was the country doc dealing with this chap, you’d probably arrive to find I’d already popped in an ICC. I always think that the findings on exam before a chest tube are a bit like the findings on vaginal exam….a secret between you and God! Ain’t noone gonna dispute findings once its in…

  6. Minh Le Cong on November 19th, 2011 21:51

    Tim, thats what I was taught when I first started retrieval medicine. The problem I found was that you are inevitably going to place ICC that were not needed and potentially increase morbidity and mortality.
    I have seen ICC end up in all sorts of places and know of a couple of cases where it did lead to a fatal outcome.

    What if the reduced AE was due to pulmonary contusion?
    So thats why I got learning how to do prehospital USS for pneumothorax. Finger thoracostomy is potentially less likely to cause complications but it may still of course. I raise it because its not well discussed even in the aeromedical literature or common teachings.

    I agree once you stick them on IPPV then its reasonable to insert a prophylactic ICC if you reasonably suspect a pneumothorax and you have to air transport them.

    I personally have no issue with what Cliff recommends. It is what I recommend after all for that scenario now.

  7. Tim Leeuwenburg on November 20th, 2011 21:59

    Yeah, I hear you – it all comes back to the utility of USS ‘out there’ rather than back in the tertiary centre…

    [Mental note to self - must track down SonoSite rep]