What occurs to the pressure in the thoracic and abdominal cavities during the Valsalva maneuver?

During the Valsalva maneuver, there is a specific process that affects the pressures in the thoracic and abdominal cavities. When an individual performs this maneuver, they forcefully exhale against a closed airway, typically through a closed mouth and nose. This action causes a significant increase in intrathoracic pressure due to the compression of the lungs. As a result, the pressure in the thoracic cavity rises significantly.

Simultaneously, the increased intrathoracic pressure affects the venous return to the heart due to reduced pressure in the thoracic veins. However, the act of straining also causes an increase in abdominal pressure because the abdominal muscles contract, pushing against the abdominal contents. Consequently, the pressure in the abdominal cavity rises as well.

Both pressures rise during the Valsalva maneuver, leading to a temporary increase in overall intrathoracic and intra-abdominal pressures. This physiological response is essential to understand, particularly in contexts such as cardiac function and venous return.