Optimal Needle Position for Decompression of Tension Pneumothorax

Background: Tension Pneumothorax (TP) can occur as a potentially life-threatening complication of chest trauma. With the risk of respiratory and cardiac arrest, an immediate temporizing intervention for this condition is required by direct Needle Decompression (ND). In 2018, the Advanced Trauma Life Support (ATLS) recommendations changed from the 2nd intercostal space in the midclavicular line (ICS2-MCL) to the 4th/5th intercostal space just anterior to the anterior-axillary line (ICS4/5-AAL), whereas the European Trauma Course (ETC) trauma guidelines and the guidelines from the Royal College of Surgeons of Edinburgh (RCSEd) in the UK still adhere to placement in the ICS2-MCL for the preferred location of ND. Both chest wall thickness of the patient and needle length both play a role in the success rate of ND.  Although it is well known that Chest Wall Thickness (CWT) increases with BMI, it is unknown if the optimal place for ND may vary with BMI.

Paper: Azizi et al. Optimal anatomical location for needle chest decompression for tension pneumothorax. Injury 2021. [Link is HERE]

Clinical Question: What is the CWT at ICS2-MCL and ICS4/5-AAL* in normal weight-, overweight- and obese patients using Point of Care Ultrasound (POCUS), and what is the theoretical success rates of ND for these locations based on standard catheter lengths?

* please note: the ICS4/5-AAL used is slightly anterior to the ATLS-recommended ICS4/5-MAL

What They Did:

• A prospective, multicenter, observational study of a convenience sample of adult patients presenting in Emergency Departments (ED) of eight Dutch hospitals during a two-week period from June 11th-23^rd, 2019
• Participating hospitals were university hospitals (n=2) or teaching hospitals (n=6)
• The CWT (from skin to pleural line) was measured bilaterally in ICS2-MCL and ICS4/5-AAL with POCUS and hypothetical success rate of ND was calculated for both locations based on standard large bore catheter used for ND

Inclusion / Exclusion:

• All adult patients (> 18 years) were eligible for inclusion if they presented to the ED of one of the participating hospitals during the study period, and provided written informed consent
• Excluded from participation were patients with (pre-existing) thoracic deformities, patients who were seriously ill requiring continuous urgent care and patients who were unable to provide consent

Outcomes:

• Primary:
  • Difference in CWT as measured by ultrasound (US) between ICS2-MCL and ICS4/5l-AAL
• Secondary:
  • Relation between CWT and BMI
  • Hypothetical ND failure rate for each anatomical location based on the length of the standard large bore catheter (45 mm and 50 mm) used in thoracocentesis.

Results:

• A total of 390 patients were included
  • 52% were male
  • Mean BMI was 25.5 (range 16.3-45.0)
  • CWT in ICS2-MCL was significantly thinner than ICS4/5-AAL in overweight- (BMI 25-30, p < 0.001), and obese (BMI > 30, p = 0.016 patients, but not in patients with a normal BMI.
  • Hypothetical failure rates for 45mm and 50mm catheters were 2.5% and 0.8% for ICS2-MCL and 6.2% and 2.5% for ICS4/5-AAL (p = 0.016 and p = 0.052 respectively).

• Difference in CWT (Primary Outcome):
  • Median CWT was 26 (range 9-52) mm in ICS2-MCL, and 26 (range 10-78) mm in ICS4/5-AAL (p<0.001)
  • Female patients had a slightly thicker chest wall than males, both in the 2nd and 4th/5th ICS, although the differences did not reach statistical significance

• Secondary Outcomes:
  • BMI in relation to CWT
    • Median CWT in ICS2-MCL (p<0.001)
      • 22 mm (range 9-41) in lean patients (BMI<25)
      • 27 mm (range 12-47) in overweight patients (BMI 25-30)
      • 35 mm (range 21-52) in obese patients (BMI>30)
    • Median CWT in ICS4/5-AAL (p<0.001)
      • 22 mm (range 10-53) in lean patients
      • 29 mm (range 13-51) in overweight patients
      • 39 mm (range 23-78) in obese patients
  • Correlation of BMI and CWT
    • Difference in mean CWT between ICS2-MCL and ICS4/5-AAL is BMI dependent
      • not significantly different in lean patients
      • significantly thicker in ICS4/5-AAL in overweight patients
      • significantly thicker in ICS4/5-AAL in obese patients

• • Relation of CWT to hypothetical (un)successful ND

• • • Of the 24 patients in whom a 45 mm IV catheter would not have penetrated the pleura in the ICS4/5-AAL, a subsequent attempt in ICS2-MCL would have been successful in 18 patients
    • There were no patients in whom a 50mm catheter would not have penetrated the pleura on both ICS4/5-AAL and ICS2-MCL.

Strengths:

• The study was performed in a heterogeneous cohort of ED patients
• US images were recorded and adjudicated by an EM physician certified in POCUS
• BMI in this cohort equals the average for the Dutch population, and is in line with previously reported values for western populations
• The authors demonstrated that the difference in CWT between both anatomical locations increases with increasing BMI in favour of 2nd intercostal-MCL

Limitations:

• It cannot be excluded that compression of the chest wall by the US probe may have influenced CWT measurements on certain instances
• The CWT may vary between various study populations. However, given the demonstrated increase in differences in CWT between ICS2-MCL and ICS4/5-AAL with increasing BMI, this will likely not influence the preferred anatomical site for needle decompression
• This study used a hypothetical failure rate. True failure to decompress a tension pneumothorax, however, may also be present due to factors other than CWT in relation to needle length, such as catheter diameter, obstruction by blood or tissue, and/or kinking- or dislodgement of the catheter, which may be related to the anatomical site chosen
• These findings cannot unequivocally disprove the ATLS recommendations, as they measured 4th/5th intercostal CWT in AAL and not just anterior of MAL. However, it is unlikely the results would have been different for MAL, as a recent meta-analysis demonstrated that the average 4th/5th intercostal CWT was thicker in MAL compared to AAL

Discussion:

• Study was powered for the primary outcome of the difference in CWT between ICS2-MCL and ICS4/5-AAL based on a non-inferiority margin of 1mm under the assumption that mean CWT is 30mm for patients with normal BMI (<25)
• This study demonstrated that the chest wall in ICS4/5-AAL measured with POCUS is significantly thicker than in ICS2-MCL in overweight- and obese subjects, and that theoretical failure rates of standard equipment to decompress a tension pneumothorax are lower for ICS2-MCL compared to ICS4/5-AAL
• These findings are in sharp contrast to the latest treatment recommendations of the ATLS, wherein placement in the 4th/5th intercostal space just anterior to the MAL is advocated for
• In countries with a higher average BMI, hypothetical failure rates for ND of the chest with a 50 mm needle are likely higher, warranting adaptations to standard equipment (e.g. using an 80 mm instead of 50 mm catheter needle)
• Although not quantified in this study, it can be assumed that placement in the ICS2-MCL will leave the catheter less prone to obstruction by blood (as patients are usually treated supine) and/or dislodgement due to arm movements
• The ICS2-MCL is harder to define anatomically, however, and therefore theoretically a catheter inserted here may not go in where intended
• Previous evidence base on the most ideal anatomic location for needle decompression is limited
  • Several studies exclusively performed in military personnel consisting of mostly young, healthy males who were not overweight or obese
  • Several studies performed on cadavers which can decrease thoracic wall composition and resultant measurements
  • CT scanning used in almost all non-cadaveric studies to estimate CWT.  Arm positioning during CT scanning can influence chest wall thickness
• When ND is warranted in a patient with rapidly deteriorating haemodynamics and a presumed tension pneumothorax, there is no time to use US to establish the optimal location for ND. When there is time to use US, ND is usually not the treatment of choice. Therefore, based on these study results, the researchers recommend performing a ND in ICS2-MCL with a 50mm (or longer) catheter as a temporizing measure in hemodynamically compromised patients when a tension pneumothorax is suspected, and when a finger thoracostomy cannot be performed immediately due to restricted (prehospital) access to the patient, or when personnel trained to perform a finger thoracostomy is not present

Author Conclusion: “In overweight- and obese subjects, the chest wall is thicker in ICS4/5-AAL than in ICS2-MCL and theoretical chances of successful needle decompression of a tension pneumothorax are significantly higher in ICS2-MCL compared to ICS4/5-AAL.”

Clinical Take Home Point: In this heterogenous patient population, ICS2-MCL seems to be the preferred anatomical location for tension pneumothorax decompression for overweight- and obese subjects compared to the ICS4/5-AAL using standard large bore catheters (45 mm and 50 mm).

References:

1. Azizi et al. Optimal anatomical location for needle chest decompression for tension pneumothorax. Injury 2021. [Link is HERE]

For More on This Topic Checkout:

• The SGEM: SGEM #339 – I Don’t Need This Pressure On – Chest Wall Thickness at Needle Decompression Site

Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter: @srrezaie)