Emergency Medical Technician (EMT) Basic Certification Practice Exam

What is the definition of pulsus paradoxus?

1. An increase in heart rate during inhalation

2. A decrease in pulse and blood pressure during inhalation

3. An irregular pulse at rest

4. A sudden drop in blood pressure upon standing

The correct answer is: A decrease in pulse and blood pressure during inhalation

Pulsus paradoxus is defined as a decrease in pulse and blood pressure during inhalation. This physiological phenomenon occurs when the pressure within the thoracic cavity changes during the respiratory cycle, significantly affecting venous return to the heart and subsequently reducing cardiac output. During inhalation, the diaphragm moves down, causing a drop in intrathoracic pressure, which can lead to enhanced filling of the right ventricle but a reduced filling of the left ventricle due to the shifting of the interventricular septum. This results in a measurable decrease in systolic blood pressure and pulse amplitude. In clinical practice, observing pulsus paradoxus can be critical, as it is often associated with conditions such as cardiac tamponade, severe asthma, and other forms of obstructive respiratory diseases. Recognizing this sign is essential for emergency responders, as it can indicate the severity of a patient’s condition and guide the appropriate interventions.