Needle decompression for tension pneumothorax in Tactical Combat Casualty Care: do catheters placed in the midaxillary line kink more often than those in the midclavicular line?

BACKGROUND: Tactical Combat Casualty Care (TCCC) is a system of prehospital trauma care designed for the combat environment. Needle decompression (ND) is a critical TCCC intervention, because previous data suggest that up to 33% of all preventable deaths on the battlefield result from tension pneumothoraces. There has recently been increased interest in performing ND at the fifth intercostal space in the midaxillary line to prevent complications associated with landmarking second intercostal space in the midclavicular line site. We developed a model to assess whether catheters placed in the midaxillary line for decompressing tension pneumothoraces are more prone to kinking than those placed in the midclavicular line because of adducted arms during military transport.
METHODS: To simulate ND, we secured segments of porcine chest walls over volunteer soldiers' chests and placed 14-gauge, 1.5-inch angiocatheters through the porcine wall segments which were affixed to either the midaxillary or midclavicular location on the volunteers. We then assessed for occlusion and kinking by flow of normal saline (NS) through the angiocatheter in situ. The angiocatheter was then transduced using standard arterial line manometry, and the opening pressures required to initiate flow through the catheters were measured. The opening pressures were then converted to mm Hg. We also assessed for catheter occlusion after the physical manipulation of the patient, by simulated patient transport.
RESULTS: We observed that there was a significant pressure difference required to achieve free flow through the in situ angiocatheter between the fifth intercostal space midaxillary line versus the second intercostal space midclavicular line site (13.1 ± 3.6 mm Hg vs. 7.9 ± 1.8 mm Hg).
CONCLUSIONS: This study suggests that the 14-gauge, 1.5-inch angiocatheter used for ND in the midaxillary line may partially and temporarily occlude in patients who will be transported on military stretchers. The pressure of 12.8 mm Hg has been documented in animal models as the pressure at which hemodynamic instability develops. This may contribute to the reaccumulation of tension pneumothoraces and ultimate patient deterioration in military transport.