From the Guidelines
The Valsalva maneuver significantly increases intrathoracic pressure, leading to a series of physiological effects on the cardiovascular system, as described in the 2018 ESC guidelines for the diagnosis and management of syncope 1. When a person performs this maneuver, they forcefully exhale against a closed glottis (closed airway), which creates substantial positive pressure within the chest cavity. The increased intrathoracic pressure has several physiological effects, including:
- Compressing the heart and great vessels
- Reducing venous return to the heart
- Temporarily increasing arterial blood pressure followed by a decrease
- Affecting cardiac output The pressure changes occur in distinct phases, as outlined in the guidelines 1:
- Initially, blood pressure rises with increased intrathoracic pressure
- Then falls as venous return decreases
- Followed by a compensatory tachycardia
- Finally, a blood pressure overshoot when the maneuver is released This mechanism is utilized clinically to evaluate autonomic function, convert certain cardiac arrhythmias, and is often performed unintentionally during activities requiring straining such as heavy lifting, defecation, or childbirth. The increased intrathoracic pressure can also affect cerebral blood flow and intracranial pressure, which explains why prolonged Valsalva can lead to dizziness or even syncope, as noted in the guidelines 1. Key points to consider when performing the Valsalva maneuver include:
- The patient should be asked to conduct a maximally forced expiration for 15 s against a closed glottis
- The haemodynamic changes during the test should be monitored using beat-to-beat continuous non-invasive BP measurement and ECG, as recommended in the guidelines 1.
From the Research
Effect of Valsalva Maneuver on Intrathoracic Pressure
- The Valsalva maneuver results in an increase in intrathoracic pressure, which incites a sequence of rapid changes in preload and afterload stress 2.
- This increase in intrathoracic pressure causes compression of the vena cava and pulmonary veins, reducing the venous backflow and gradually decreasing the arterial pressure 3.
- The Valsalva maneuver also alters the systemic and cerebral circulations significantly, resulting in changes in intracranial pressure and cerebral perfusion pressure 4.
- Transient increases in intrathoracic pressure due to the Valsalva maneuver can decrease hemodynamic determinants of myocardial oxygen demand and increase the myocardial oxygen supply:demand ratio 5.
- A brief Valsalva maneuver may actually protect arteries located in the thorax and in the brain by diminishing transmural pressure acting across these vessels, although individual variability exists 6.
Key Findings
- Increased intrathoracic pressure is a direct result of the Valsalva maneuver 2, 3.
- The maneuver affects both systemic and cerebral circulations, leading to changes in various hemodynamic parameters 2, 4, 5.
- The Valsalva maneuver may have protective effects on certain arteries due to decreased transmural pressure, but this can vary between individuals 6.