Describe pulsus paradaxus pulse volume?

Pulsus Paradaxus: Pulse volume becomes smaller in inspiration and larger in expiration. This is an exaggeration of normally occurring phenomenon and is produced either by impaired diastolic filling of ventricle as typically in constrictive pericarditis, pericardial effusion or due to decreased lung compliance, as in advanced emphysema large pleural effusion etc. In a typical case applying graded pressure on brachial artery while palpating radial artery for disappearance or reappearance of pulse wave may be easily evident. In mild cases when difference is small like 10inr11 or below application of a sphygmonietric cuff on the arm and slow decompression will easily demonstrate appearance or disappearance of palpable pulse at wrist. Normally a difference of 10mm is accepted as within physiological limits and becomes pathological beyond 10 mm of Hg.

Figure: Haemodynamic mechanisms in development of pulsus paradoxus