*5.4.2 Procedure*

Left lateral recumbency (to minimize the movement) and left-side approach are recommended because the right ventricular wall is much thinner than the left ventricular wall, so it is easier to penetrate it unknowingly as you advance the needle and catheter. It is easier to recognize iatrogenic puncture of the left ventricle than of the right ventricle. The oxygenated blood in the left ventricle is bright red. Both right ventricular blood and pleural effusion are dark red, and the high left ventricular pressure usually results in a pulsatile, high-velocity flashback into the catheter, making it obvious if you have penetrated the left ventricle.

If approach is made by the right side, the landmark for performing pericardiocentesis is the "cardiac notch" between the right cranial and caudal lung lobes where the risk of lung puncture is diminished.
