From the Research
Squatting increases venous return to the right atrium by compressing the veins in the lower extremities and increasing intra-abdominal pressure, as demonstrated by the most recent study in 2023 1.
Mechanism of Action
When a person squats, the flexion at the hips and knees compresses the femoral veins, forcing blood from the peripheral circulation toward the heart. Simultaneously, the increased intra-abdominal pressure created by the compressed abdominal contents pushes blood from the splanchnic circulation into the inferior vena cava. This dual mechanism results in an immediate increase in preload to the right heart, enhancing ventricular filling and subsequently increasing cardiac output through the Frank-Starling mechanism.
Physiological Effects
The physiological effect is particularly beneficial in certain cardiac conditions like hypertrophic cardiomyopathy and tetralogy of Fallot, where increased venous return can temporarily improve symptoms. Additionally, squatting increases systemic vascular resistance, which further contributes to hemodynamic changes. These effects reverse promptly when standing resumes, making squatting a transient but effective maneuver to augment cardiac preload when needed.
Clinical Implications
The study by 1 highlights the importance of considering venous return physiology in clinical assessments of volume responsiveness. The use of echocardiography and venous return physiology can provide a more comprehensive understanding of the effects of squatting on venous return and cardiac output. This knowledge can be applied in various clinical settings, such as in the management of patients with cardiac conditions or in the assessment of volume responsiveness in critically ill patients.
Key Findings
- Squatting increases venous return to the right atrium by compressing the veins in the lower extremities and increasing intra-abdominal pressure 1.
- The pressure gradient for venous return (VRdP) is an important determinant of stroke volume changes during a preload challenge 1.
- Impaired right ventricular function and increased intra-abdominal hypertension can confound the relationship between VRdP and stroke volume changes 1.