This man has pulsus paradoxus, a sign in which blood pressure decreases drastically during inspiration. Pulsus paradoxus is a classic sign of pericardial tamponade.
When fluid (often blood) has pooled around the heart, the heart struggles to expand and fill with blood. This becomes a bigger problem for the right ventricle during inspiration, because the right side of the heart receives increased venous return during inspiration. Because there is fluid preventing the right ventricle from expanding outward, the only other place it can expand to accommodate is by pushing on the septum, shrinking the size of the left ventricle. This causes decreased BP when the left ventricle contracts during that cardiac cycle.