Where is the primary site for needle thoracostomy on the affected side?

• A. Primary: 4th intercostal space mid-axillary line of the affected side
• B. Secondary: 2nd intercostal space mid-clavicular line of the affected side
• C. 5th intercostal space mid-axillary line
• D. 3rd intercostal space mid-clavicular line

Answer: (A)

Rapid relief of pressure in a tension pneumothorax is achieved by creating a direct opening into the pleural space from the chest wall. The safest and quickest entry point on the affected side is along the lateral chest wall at the mid-axillary line. This location provides a straight path to the pleural cavity, minimizes risk to the heart and major vessels, and keeps you away from the diaphragm. It also tends to have a thinner chest wall, which helps successful decompression with a needle. The anterior approach near the collarbone places you closer to the heart on the left and to major vessels, increasing injury risk, and other described sites are used less commonly as the first choice. So the primary site is the lateral chest wall along the mid-axillary line on the affected side.