The optimal insertion site for tube thoracostomy is at the mid-axillary line in the triangle of safety. This avoids any major nerves or arteries aside from the intercostal vessels. Ultrasound-guided localization of this site performed better than palpation.
In semi-elective chest tube placement, many experts are recommending bedside ultrasound prior to chest tube placement to optimize insertion site selection. Some of the known complications of tube thoracostomy include infra-diaphragmatic placement of the chest tube that may result in injury to the diaphragm or subdiaphragmatic organs such as the liver or spleen. Traditionally, the nipple level brought out to the mid-axillary line has been used as a level that approximates where the 4th intercostal space (ICS) is. However, the nipple level is not necessarily accurate in women or men with large breasts or in obese men. Alternative landmarks include the inframammary line or three fingerbreaths above the xiphoid notch brought out to the mid-axillary line. These are all reasonable landmarks to approximate the best insertion site for chest tube placement. Other variables that can come into play include a patient with an intra-abdominal process such as bowel obstruction, severe acute pancreatitis or any cause of abdominal compartment syndrome that can cause elevation of the diaphragms.
For all these reasons, ultrasound identification of the diaphragm is critical in semi-elective chest tube placement. At the same time, one can use color doppler flow to try and identify the intercostal artery at the proposed insertion site. Usually this far lateral, the intercostal vessels are protected in the rib groove but occasionally the intercostal artery can be more exposed and vulnerable to injury during tube thoracostomy.
Tube thoracostomy has a complication rate of up to 30% in some studies. This study of junior emergency medicine residents demonstrated that they correctly identified the 4th ICS in a model patient by palpation only 48% of the time. Whereas, ultrasound-guidance identified the proper site for tube thoracostomy 91% of the time. Moral of the story: use ultrasound to help identify the proper insertion site for tube thoracostomy.
Taylor L.A. et al. Ultrasound-guided thoracostomy site identification in healthy volunteers. Critical Ultrasound J. 2018; 10: 28