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Date: July 29th, 2021

Reference: Azizi et al. Optimal anatomical location for needle decompression for tension pneumothorax: A multicenter prospective cohort study. Injury 2021

Guest Skeptic: Dr. Robert Edmonds is an emergency physician in the Air Force in Ohio.  This is Bob’s 14th episode cohosting the SGEM.

DISCLAIMER: THE VIEWS AND OPINIONS OF THIS PODCAST DO NOT REPRESENT THE UNITED STATES GOVERNMENT OR THE US AIR FORCE.

Case: You are driving home from a busy shift and see a car collision occur right in front of you.  The driver is a restrained self-extricated male who lost control of his vehicle into a light post and the vehicle’s airbags deployed.  After safely pulling over and having a bystander call 911, you evaluate the patient.  He is speaking in full sentences without confusion, has a strong, rapid pulse, significant pain in his chest and is having a very hard time breathing.  As you wait for EMS to arrive, you quickly dash back to your car to retrieve your stethoscope and an angiocatheter you have in your glovebox.  You notice a marked difference between breath sounds on the left side and decide the patient needs treatment for a tension pneumothorax.  After obtaining consent from the patient, you debate whether to decompress at the second intercostal space in the midclavicular line as you originally learned, or in the fourth/fifth intercostal space midaxillary line as per the current ATLS guidelines.

Background: The latest ATLS guidelines were published in 2018. We covered them on the SGEM Xtra with Dr. Neil Parry. There were several changes to the new guidelines but one of them was changing the location for needled decompression for adult patients.

Needle thoracostomy is subject to several complications compared to a tube thoracostomy primarily due to the shorter length of the needle as well as the smaller lumen, so site selection has focused on finding a short distance and a site unlikely to kink or get dislodged.

Dr. Richard Malthaner

We have covered chest tube thorocostomy a couple of times on the SGEM with Dr. Richard (Thoracic) Malthaner. SGEM#129 looked at where to put the chest tube on trauma patients and if a post-procedure chest Xray (CXR) was required. The conclusion from that episode was to put the tube on the correct side, within the triangle of safety, and within the pleural space. Continue to obtain a CXR post chest tube knowing it will probably not change management. Be more concerned if the patient is doing poorly or the tube is not draining.

The other episode on chest tubes was SGEM#300. The clinical question was does everyone with a large first-time spontaneous pneumothorax need a chest tube? The answer from that episode was It is reasonable to provide conservative management (no chest tube) in a patient with large first-time spontaneous pneumothoraxes if you can ensure close follow-up.

The changes in the ATLS guidelines were based in part on a small study (n=20) utilizing cadavers [1]. There were also studies using CT scans showing a preference for the fourth/fifth ICS AAL [2,3].  These studies were limited by heterogeneity (I2 83%-98%), possible publication bias, and not being randomized trials.

These authors are adding to the literature by utilizing ultrasound on live patients. This could reduce some of the potential confounders in prior studies that were exclusively cadavers which may have differences in CWT due to post-mortem changes.

The previous studies also focused on homogenous populations like military members and are therefore less generalizable to the general population. Additionally, by using ultrasound instead of CT, some of the confounders from arm placement during CT were reduced. 

Clinical Question: Is the chest wall thickness at the second intercostal space in the midclavicular line not thicker than the fourth/fifth intercostal space anterior axillary line?

Reference: Azizi et al. Optimal anatomical location for needle decompression for tension pneumothorax: A multicenter prospective cohort study. Injury 2021

  • Population: A convenience sample of all adults presenting to one of the eight participating hospitals over a two-week period. (June 11-23, 2019)
    • Excluded: Patients with pre-existing thoracic deformities, patients who were seriously ill requiring continuous urgent care, and patients who were unable to provide consent
  • Intervention: Chest wall thickness at the second intercostal space in the midclavicular line
  • Comparison: Chest wall thickness at the fourth/fifth intercostal space anterior axillary line
  • Outcome:
    • Primary Outcome: Median CWT in ICS2-MCL and ICS 4/5 AAL
    • Secondary Outcomes: BMI 25-30 CWT, BMI 30+ CWT, hypothetical failure rates of needle decompression

Authors’ Conclusions: “In overweight- and obese subjects, the chest wall is thicker in ICS 4/5-AAL than in ICS2-MCL and theoretical chances of successful needle decompression of a tension pneumothorax are significantly higher in ICS2-MCL compared to ICS 4/5-AAL.”

Quality Checklist for Observational Study:

  1. Did the study address a clearly focused issue? Yes
  2. Did the authors use an appropriate method to answer their question? Unsure
  3. Was the cohort recruited in an acceptable way? Unsure
  4. Was the exposure accurately measured to minimize bias? Yes
  5. Was the outcome accurately measured to minimize bias? Yes/Unsure
  6. Have the authors identified all-important confounding factors? No
  7. Was the follow up of subjects complete enough? Yes
  8. How precise are the results? Precise
  9. Do you believe the results? Yes
  10. Can the results be applied to the local population? Unsure
  11. Do the results of this study fit with other available evidence? No

Results: There were 390 patients available for analysis in this study. Mean age was 51 years, 52% were male and the mean BMI was 25.5.

Key Result – There was no statistical difference in mean chest wall thickness between the second ICS-MCL and the fourth/fifth ICS-AAL

  • Primary Outcome: Median chest wall thickness (CWT)
    • 26mm (IQR 21-32) ICS2-MCL vs 26mm (IQR 21-33) ICS 4/5 AAL (p<0.001)
  • Secondary Outcomes:
    • Median CWT BMI 25-30: Chest wall was thinner at ICS2-MCL 27mm vs ICS 4/5-AAL 29mm
    • Median CWT BMI 30+: Chest wall was thinner at ICS 2-MCL 35 mm vs. ICS 4/5-AAL 39 mm
    • Hypothetical Failure Rates of Needle Decompression

1. Convivence Sample – The authors state they used a convenience sample of patients presenting to the ED of eight hospitals during a two-week period June 11-23, 2019. The words “convenience” sample often refer to limited hours of enrollment (not nights/weekends and holidays usually). They did not explicitly state what they meant by convenience sample in the published manuscript. Selection bias could have been introduced using this methodology.

2. Angle of Attack – The authors mention the CWT and then use this to extrapolate the hypothetical rate of needle decompression failure for the two sites. This assumes the clinician performing the needle decompression enters the skin in a perpendicular approach and goes the shortest distance possible to the pleura. It is reasonable to suspect that the patient who is receiving needle decompression rather than a chest tube is further from definitive care or in a greater degree of extremis than a stable patient with a spontaneous pneumothorax who ambulated into the ED complaining of chest pain and difficulty breathing.  It’s likely that not all needles used for needle decompression are placed perfectly perpendicular to the site of choice, and it seems reasonable to conclude that there could be a significant difference in the actual angle of attack the needle takes when comparing the two sites.  This makes the authors’ hypothetical rate of ND failure based purely on CWT a little less definitive.

3. Site Selection – They evaluated the site previously recommended by ATLS (second ICS-MCL) but compared it to a different site than the new ATLS recommendation. These authors looked at fourth/fifth ICS-AAL instead of ATLS recommended fourth/fifth ICS-MAL). The Laan SRMA mentions how “…in our analysis of the CWT reported at different locations, we found that the mean CWT was smallest at ICS4/5-AAL, thicker at ICS4/5-MAL, and thickest at ICS2-MCL. Despite this observed tendency, the difference in CWT was not statistically significant (P=.08).” So, if the authors truly intended to support use of the second ICS-MCL over the more lateral and inferior sites, the better comparison would have been fourth/fifth ICS-MAL based on previous evidence.

4. Under Pressure – The authors used ultrasound to measure the CWT at both sites.  They state that the ultrasound probe was placed “without any compression” and exactly perpendicular to the chest wall.  Although every effort was likely made to reduce compression, these two sites do differ in how lateral they are, and it is possible that some compression of tissues did occur during measurement despite the best of efforts.  This challenges the accuracy of the measurements between the two sites.

5. Clinically Important – While this is an interesting study using POCUS to determine CWT and generate a hypothetical failure rate, a much better study would be a randomized trial. Randomize patients into getting the needle decompression at the second ICS-MCL or the fourth/fifth ICS-MAL as per the latest ATLS guidelines. The primary outcome could be successful decompression. If one site is superior to another then a further larger trial could be done looking at all-cause mortality as the primary outcome.

Comment on Authors’ Conclusion Compared to SGEM Conclusion: We are hesitant to change practice based on a subgroup analysis and find insufficient evidence to reject the ATLS guidelines for needle thoracostomy placement site. This is recognizing that there is not strong data to support the ATLS guideline recommendation.

SGEM Bottom Line: This study does not support the claim that the second ICS-MCL is thicker than the fourth/fifth ICS-AAL.

Case Resolution: Using the patient’s nipple as a landmark, you identify the fourth ICS and scrub an alcohol pad over the midaxillary line, then you insert the angiocatheter.  You are rewarded with a rush of blood speckled air, and after the patient recovers from the pain, they start breathing with less labor.

Dr. Robert Edmonds

Clinical Application: This will not change our practice. It is good to recognize that the evidence is weak to support the “best” location for a needle thoracostomy. The most important thing is to decompress the lung.

What Do I Tell My Patient? You have a life-threatening condition involving a dropped lung and I must fix it now so you can survive long enough to get to a hospital where they can get a more permanent solution involving a longer tube that will drain out the air that is leaking out of your lung and into your chest.

Keener Kontest: Last weeks’ winner was Zach Lyman. He knew actor Cesar Romero was the famous Batman villain (the Joker) who died of pneumonia in 1994, aged 86.

Listen to the podcast this week to hear the trivia question. Email your answer to TheSGEM@gmail.com with “keener” in the subject line. The first correct answer will receive a cool skeptical prize.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.

References:

  1. 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. J Trauma. 2011 Nov;71(5):1099-103; discussion 1103. doi: 10.1097/TA.0b013e31822d9618. PMID: 22071914.
  2. Laan DV, Vu TD, Thiels CA, Pandian TK, Schiller HJ, Murad MH, Aho JM. Chest wall thickness and decompression failure: A systematic review and meta-analysis comparing anatomic locations in needle thoracostomy. Injury. 2016 Apr;47(4):797-804. doi: 10.1016/j.injury.2015.11.045. Epub 2015 Dec 13. PMID: 26724173; PMCID: PMC4976926.
  3. Misgav Rottenstreich et al. “Needle Thoracostomy in Trauma.” Military Medicine. 180, 12:1211, 2015