On the Difference Between the Posterior Mediastinum and the Posterior Left Lung and Rib Cage

Question: What is the difference between the posterior mediastinum and the posterior left lung & rib cage and why do we strive to expand it?

We define the posterior mediastinum as the area in the thorax that provides positional support for organs, vessels, and nerves from T4 to T12. Its boundaries are: the pericardium anteriorly; the diaphragm inferiorly; the transverse thoracic plane “T4” superiorly; the vertebral column posteriorly; and the pleura laterally. The posterior mediastinum, therefore, is an area between the right and left lungs. This area is more closed and anteriorly positioned on the left vs. right in a right BC pattern and closed bilaterally in a B PEC pattern. The challenge is this: because it can’t be sensed or felt, how does one accomplish expansion of the posterior mediastinum, especially on the left? The short answer is through expansion of the left posterior lung and rib cage, which we assign as a reference, or sensorium, in many of our non-manual techniques.

Posterior mediastinum expansion first requires activation of L IOs/TAs to establish a left ZOA to: IR the left ribs in front and ER the left ribs in the back and to improve the respiratory role of the left diaphragm. This emphasis better biases air flow into the left posterior lung and better expands the left posterior rib cage. Furthermore, through costo-vertebral coupling, the thoracic vertebrae will be directed more to the right (transverse plane) and posterior (sagittal plane), therefore re-establishing a normal thoracic kyphosis and creating more posterior mediastinum expandability and, thus, allowance for the posterior lung to move and migrate into. This expandability of the posterior mediastinum’s ribcage, and increase in potential room for lung inflation, allows the left posterior lung to alternately inflate and deflate into the more expansive posterior mediastinum area. The alternating compression-decompression provided by the left posterior lung into and out of this expanded space keeps the vessels of the “main highway” (sympathetic trunk, esophagus, circulatory and lymph vessels) more viable. These vessels thrive on this oscillatory compression-decompression for their health and function.

Louise Kelley, DPT, PRC and Dan Houglum, MSPT, ATC/L, PRC