Page 75 - Journal of Special Operations Medicine - Fall 2015

for five different lengths of needle for comparison (note a common and correctable cause of failure of NCD: in-
that an angiocatheter has a 50mm needle and a 45mm adequate catheter length to penetrate through the chest
catheter). Therefore, although initial decompression wall into the pleural space. This survey found that the
might be successful with a 50mm needle, particularly in UK military now uses a device long enough to penetrate
the L 2ICS, once this was removed and the catheter left the chest wall, Air Release System (North American Res-
in place, one in 13 (8%) may not be functional. cue), but we need to advise on a safe maximum length to
avoid major complications.
Mean depth to first critical structure, if the device was
inserted perpendicularly to the skin, and the depth to Devices used to perform emergency NCD vary from
nearest critical structure, if the device was inserted at large-bore needles and intravenous catheters to pur-
an angle, was 103mm (median, 99mm; IQR, 86mm– posefully designed systems up to 110mm long able to
119mm) and 88mm (median, 87mm; IQR, 79mm– endure harsh prehospital environments. Interestingly,
96mm), respectively. Figure 2 demonstrates the “safe Hatch et al. propose a different approach, present-
12
zone,” which is between the minimum length required ing promising early data from porcine studies for use
for effective penetration into the pleural space and the of a 5mm laparoscopic trocar as a more robust and ef-
maximum length allowed to prevent complications. fective alternative device. The recommended length of
The shortest distance to a critical structure was 51mm, trocar for clinical use, along with improved profiling, is
which could have led to potential perforation of the still to be evaluated in clinical studies, but a needleless
diaphragm. Two further patients may have suffered device could help eliminate the incongruence between
diaphragmatic perforation if the needle was placed an- needle and catheter length, giving greater clarity to
gularly (59mm and 60mm). Therefore, 97% of soldiers recommendations. The most common device currently
in our cohort (61 of 63 patients) would not experience used by British combat medics on the frontline is the
damage to critical structures with a needle length less 81.2mm Air Release System (North American Rescue).
than 60mm (Figure 3). However, this length would potentially damage vital
structures in 29% of our cases. The design of longer
Figure 3 Graphical representation of maximum (critical catheters used accurate data based on the CWT, where
structures) and minimum (chest wall thickness) depths for is has been shown in a study by Harcke et al. that an
safe needle thoracostomy. 80mm angiocatheter will penetrate the pleural cavity in
99% of adult patients (101 US military men). However,
7
that study did not examine the maximum safe length
and, therefore, their recommendations must be taken in
context. A CT study conducted in 2011 that looked at
80mm needle placement at the fourth anterior axillary
line again showed a 96% success rate; however, it dem-
onstrated that the left ventricle would be penetrated in
30 of 32 cases at the closest angle. The majority of
13
studies have been performed on a US population, mak-
ing extrapolation of data to a UK Service population
potentially unreliable. Harcke et al. further emphasized
the disparity in study populations, finding that US Ser-
vicemembers have a greater-than-average CWT (possi-
bly related to a culture of weight-lifting, fitness training,
Discussion
and supplement use rather than the UK predisposition
A common, potentially fatal complication of trauma for running). A higher adult obesity rate may also ac-
7
sustained on the frontline is TP. Traditional devices count for population differences between studies; more
used to decompress TP may not be adequate for some than one-third of the overall US population (34.9%)
14
Servicemembers because of increased CWT. Leading compared with 25% of UK adults are obese, which
15
guidelines and protocols in emergency care consistently may, in part, be why this study finds a shorter optimal
recommend the use of large-caliber needles to perform length device than US studies.
first-line needle chest decompression for TP. However,
4,5
there remains no evidence-based definitive guidance for There are many published US studies that have used
optimal catheter length for successful emergency NCD. CWT measured on ultrasound and CT to indirectly pre-
Reasons for NCD failure are multifactoral and include dict optimal catheter length for decompression of TP.
external catheter compression by subcutaneous emphy- These studies report varying failure rates. In 2009, a
sema or chest wall hematomas, catheter blockage by tis- retrospective US study predicted a likely failure rate of
sue or blood, and localized TP. This survey focuses on 50% when using a 44mm angiocatheter to penetrate the
6

Optimal Device Length for Needle Thoracostomy 63