We Don't Know the Midclavicular Line

The Gist:  Needle decompression for tension pneumothorax should be taught at the fourth or fifth intercostal space at the anterior axillary line (4/5ICS AAL). 

• Note: This post will not detail critiques that needle decompression may be overused or the needle vs thoracostomy debate.

Historical teaching instructs providers to place a needle in the second ICS at the mid-clavicular line (2ICS MCL) for tension pneumothorax [1,2]. Free Open Access Medical Education (FOAM) sources such as Emergency Medicine Ireland have preached the more lateral approach for years; yet this teaching has not spread widely (outside of military circles where there seems to be better adoption). Change is difficult, particularly when it involves re-educating thousands of providers and it seems like this is the primary driver behind the 2ICS MCL remaining as the typical site for needle decompression..  However, several potential problems exist with the mid-clavicular approach that warrant consideration for assuming 4/5ICS AAL as the primary initial placement for needle decompression.

A: Where I see most needles placed, B: 2ICS MCL, C: 5ICS AAL

We may not be able to reach the pleura [3-5].  The chest wall may be particularly thick at the 2ICS MCL, particularly as the average BMI in many nations grows.  Researchers have looked at this question for years through a couple of means - measuring the depth at the 2ICS MCL on CT scans of trauma patients compared with alternative sites. The 2ICS MCL is generally 1.3 cm thicker than 5ICS AAL. 

• This discrepancy was not solely seen in the morbidly obese.  In fact, it was seen consistently across all four BMI quartiles tested, and at the traditional insertion site, needle decompression would have been extremely difficult with any eccentric placement using a standard needle in all but the lowest BMI quartile [3].

How often would the needle fail?  A systematic review and meta-analysis in Injury 2015 by Laan et al looked at 17 studies, generally cadaveric or radiographic, and found that a standard 5 cm catheter used for needle decompression at the 2ICS MCL would fail 38% (24–54%) of the time compared with only 13% (8–22%) at ICS4/5-AAL (p= .01) [5].

• The British Thoracic Society Guidelines (2010) even remark “a standard 14 gauge (4.5 cm) cannula may not be long enough to penetrate the parietal pleura..with up to one-third of patients having a chest wall thickness >5 cm in the second interspace.”
• In some places, the failure rate may be even higher secondary to obesity [5].

What about a longer needle?  Many catheters used for needle decompression are 5 cm in length; however, some have access to 8 cm angiocatheters.  A analysis by Clemency and colleagues found that in order to achieve a success rate of 95%, we would need a catheter at lease 6.4 cm in length [8].  Similarly, Laan and colleagues conducted a pre-post retrospective study in an EMS system that switched from using 5 cm catheters to 8 cm catheters with an increase in success rate (48% vs 83%) [6].  For a life saving, last ditch effort, I'm not sure that 95% success rate is adequate when alternatives exist.

We don’t identify this site well [10,11].  A 2005 paper by Ferrie and colleagues had 25 emergency physicians name the correct side for needle thoracentesis and label this site with a pen on a male volunteer (erased between providers).  Nearly all participants were ATLS certified within the past 10 years.  

• 88% (n=22) named the correct site (one additional person did name the 5ICS AAL).
• Only 15 of the 25 participants (60%) could correctly identify the 2ICS MCL [10].   

In another study, Inaba and colleagues trained 25 US Navy corpsmen on needle decompression, using both the 2ICS MCL and the 5ICS AAL. The corpsmen then performed needle decompression at both sites on randomly selected cadavers, bilaterally.  

• Mean distance from the correct location: 3.1 cm 2ICS MCL vs 1.2 cm 5ICS AAL
• Correct placement (ICS +/- 5 cm):  15/50 (30%) 2ICS MCL vs 41/50 (82%) 5ICS AAL
• Limitations: This study had multiple outcomes and no power analysis was performed [11]

I think much of this is because we underestimate the length of the clavicle.  It's easier when you can see the chest wall bones but we don't have this advantage in the clinical setting.  On a person, the midclavicular line often seems fairly lateral.  

Important structures surround the 2ICS MCL.  As mentioned above, we seem to have a tough time finding the 2ICS MCL [8,9]. There are important structures in this vicinity, particularly if the tendency is to go more medial than the actual midclavicular line, including the internal mammary artery and contents of the superior mediastinum.  Naturally, should an individual placing a needle in the 4/5ICS AAL go too caudal the possibility exists for the needle to enter the liver or spleen but the study by Inaba and colleagues suggest we may be better able to identify this space [9].

Given the literature, it seems that at this time should a needle be placed aiming for the 2ICS MCL for needle decompression and fail, this is a failure of education and changing our knowledge base rather than a patient-based failure. We should know better.

References:

1. MacDuff A, Arnold A, Harvey J. Management of spontaneous pneumothorax: British Thoracic Society pleural disease guideline 2010. Thorax. 2010;65(Suppl 2):ii18–ii31.
2. Advanced Trauma Life Support, 9th ed. 
3. Inaba K, Ives C, McClure K, Branco BC, Eckstein M, ShatzD, Martin MJ, Reddy S, Demetriades D. Radiologic evaluation of alternative sites for needle decompression of tension pneumothorax. Arch Surg. 2012;147(9): 813Y818.
4. Inaba K, Branco BC, Eckstein M, Shatz DV, Martin MJ, Green DJ, Noguchi TT, Demetriades D. Optimal positioning for emergent needle thoracostomy: a cadaver-based study. JTrauma. 2011;71(5):1099Y1103; discussion 103.
5. Laan D V., Vu TDN, Thiels CA, et al. Chest wall thickness and decompression failure: A systematic review and meta-analysis comparing anatomic locations in needle thoracostomy. Injury. 2015:14–16. 
6.  Laan D, Berns KS, Habermann EB. Needle thoracostomy: Clinical effectiveness is improved using a longer angiocatheter. 2015. doi:10.1097/TA.0000000000000889.
7. Hecker M, Hegenscheid K, Völzke H, et al. Needle decompression of tension pneumothorax. J Trauma Acute Care Surg. 2016;80(1):119–124. doi:10.1097/TA.0000000000000878.
8. Carter TE, et al. Needle Decompression in Appalachia Do Obese Patients Need Longer Needles? West J Emerg Med, 2013; 14(6): 650–2
9. Clemency BM, Tanski CT, Rosenberg M, May PR, Consiglio JD, Lindstrom HA. Sufficient catheter length for pneumothorax needle decompression: a meta-analysis. Prehospital and disaster medicine. 30(3):249-53. 2015.
10. Ferrie EP, Collum N, McGovern S. The right place in the right space? Awareness of site for needle thoracocentesis. Emerg Med J. 2005;22(11):788–789.
11. Inaba K, Karamanos E, Skiada D, et al. Cadaveric comparison of the optimal site for needle decompression of tension pneumothorax by prehospital care providers.