The reason for the decrease in systolic blood pressure during inspiration is explained in this article : Inspiratory decrease in systolic blood pressure and pulse volume – Mechanism

Mechanism of pulsus paradoxus:

1. In cardiac tamponade
   • Tense fluid in the pericardial sac impairs ventricular filling
   • Also, the negative intrathoracic pressure is not well transmitted to the pericardial sac
   • Fall in pulmonary venous pressure is more than the fall in left atrial pressure
   • Hence filling of the left atrium and in turn the left ventricle is decreased resulting in decrease in stroke volume more than normal
2. In obstructive pulmonary disease
   • There is exaggeration of the inspiratory decrease in intrathoracic pressure
   • Hence the fall in stroke volume and blood pressure is more

What is the paradox?
Pulsus paradoxus is an exaggeration of the normal variation in the systolic blood pressure and hence it is not truly paradoxical.

1. Inspiratory decrease in systolic blood pressure and pulse volume – Mechanism
2. Frusemide in left ventricular failure
3. Reverse Bernheim effect

Mechanism

• During inspiration there is increased venous return (due to negative intrathoracic pressure)
• right ventricles expands more
• interventricular septum is pushed to the left side (Reverse  Bernheim effect)
• This decreases the left ventricular volume
• Also the pooling of blood in the pulmonary circulation occurs, decreasing amount of blood reaching left ventricle

This causes decrease in stroke volume of left ventricle, thus decreasing the systolic blood pressure. The maximum decrease in blood pressure that is considered normal is 10 mm Hg. If the decrease is more than 10 mm Hg, it is called pulsus paradoxus.

1. Pulsus paradoxus
2. Frusemide in left ventricular failure
3. Frusemide

Can occur due to

• Physiologically during inspiration due to increased filling of the right ventricle (because of increased venous return)
• pulmonary embolism

1. Bernheim effect
2. Inspiratory decrease in systolic blood pressure and pulse volume – Mechanism
3. Pulsus paradoxus

1. Reverse Bernheim effect
2. Left ventricular hypertrophy
3. AAA

Straw coloured pericardial fluid

Straw coloured pericardial fluid aspirated into a syringe. Straw coloured fluid indicates an exudative effusion and tuberculosis is an important cause.

1. Pleural effusion – left
2. Multiple air-fluid levels in intestinal obstruction
3. Minimal pleural effusion

CI = CO/BSA

1. Ankle brachial index
2. Aedes aegypti Index
3. CI

1. Pleural effusion – left
2. Frusemide in left ventricular failure
3. Cardiac Index

1. CO
2. CI
3. Cardiac Index

abbreviation, expansion

1. Most common site of aortic aneurysm
2. ICD
3. Bernheim effect

Abdominal aortic aneurysm is known by the acronym: AAA

1. AAA
2. Bernheim effect
3. Unfolding of arch of aorta