What is defined as a strain against a closed airway combined with muscular contraction?

The Valsalva maneuver is characterized by the act of forcefully exhaling against a closed airway while simultaneously contracting the muscles in the abdomen and chest. This combination of actions leads to an increase in pressure in the thoracic cavity, which has various physiological effects, such as influencing heart rate and venous return. The maneuver is often used in clinical settings to assess cardiovascular function and can also occur during activities like heavy lifting or straining.

In contrast, diaphragmatic breathing focuses on the use of the diaphragm to enhance ventilation without the pressure build-up associated with the Valsalva maneuver. Intrapleural pressure refers to the pressure within the pleural cavity and is different from the actions described in the question. Thoracic expansion relates to the increase in volume of the thoracic cavity during breathing but does not involve the specific strain against a closed airway or muscular contraction described in the Valsalva maneuver. Thus, the definition aligns precisely with the characteristics of the Valsalva maneuver.