Many of us have encountered a patient with a tension pneumothorax who required needle decompression in the field. This lifesaving skill should be familiar to all ALS personnel. After diagnosing a tension PTX based on mechanism of injury combined with physical exam findings including absent breath sounds, abnormal vital signs….tachycardia, tachypnea, hypotension and hypoxia (you will almost never see JVD or tracheal deviation) treatment must be initiated immediately. Traditionally prehospital providers used a 14g 2inch IV catheter to perform the chest decompression by placing the needle between the second and third intercostal space in the midclavicular line; however that catheter length lead to a very high failure rate. Our services have addressed this problem by swithcing to 10g 3inch catheters for chest decompression. The longer length increases success of entering the pleura while the larger diameter is less likley to get clogged by blood.
One question that I have always wondered was, would changing the location on the chest where we place the catheter have any effect on our success rates? In the ED chest tubes are most commonly placed in the mid-AXILLARY line in the 4th or 5th intercostal space. I am very comfortable placing large bore chest tubes in that area so would there be a benefit to placing needle chest decompression devices here?
This question was discussed in the October 2011 issue of Academic Emergency Medicine by Sanchez et al. This group preformed a retrospective study of 159 ED patients who received a CT of the chest after blunt trauma. They measured the distance from the skin to the pleura at the anterior second intercostal space and at the midaxillary line. The results:Anterior Midaxillary Right 46mm 64mm Left 45mm 62mm
It looks like the anterior approach does have the shortest distance from surface to pleura and it would be the best spot to place your needle decompression. Moreover, at only 1.8inches the anterior approach should be easily accomplished with a 3 inch needle. It is easy to see how a 2 inch needle could lead to problems both in placing the device initially but also with it becoming dislodged during transport.
What options are available if you are unable to access the pleura with standard techniques and your patient is dying from a tension PTX? One option would be to use a longer pericardiocentesis needle to access the chest. If an EMS physician is available a digital thoracostomy could be preformed with equipment commonly found on all ambulances. In this technique an incision is made in the midaxillary line and the tissues are dissected down to the rib. A blunt technique (typically a hemostat) is then used to puncture the pleura followed by insertion of a finger into the chest cavity to dilate and enlarge the opening and to manually confirm that the plural cavity has been entered.
Once a needle decompression has been preformed it is vital to leave the catheter in place to prevent the tension pneumothorax from re-developing. Tension PTX is one of the most common causes of EMS preventable death in trauma patients (along with exsanguination from extremity hemorrhage). Having a low threshold to perform this lifesaving technique in patients with trauma and signs/symptoms of tension physiology can be lifesaving!