From the Guidelines
Squatting increases intrathoracic pressure by mechanically compressing the abdomen and pushing the diaphragm upward into the thoracic cavity, thereby increasing venous return, cardiac output, and arterial blood pressure. This effect is supported by the physiological principles outlined in the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope, which mentions that physical counter-pressure maneuvers, such as squatting, can increase blood pressure in patients with neurogenic orthostatic hypotension 1. The mechanism by which squatting achieves this effect involves the external pressure exerted by the thighs on the abdomen, which is then transmitted to the thoracic cavity, reducing its volume and increasing the pressure within the chest. Key physiological effects of this increased intrathoracic pressure include:
- Increased venous return to the heart
- Increased cardiac output
- Increased arterial blood pressure These effects can have significant implications for various cardiac conditions and overall cardiovascular function, particularly in maintaining blood pressure and reducing symptoms of orthostatic hypotension during positional changes, as noted in the context of neurogenic OH 1.
From the Research
Effect of Squatting on Intrathoracic Pressure
- The provided studies do not directly address the effect of squatting on intrathoracic pressure 2, 3, 4, 5, 6.
- However, it can be inferred that squatting may increase intrathoracic pressure due to the increased venous return and cardiac output associated with this posture 2, 4.
- Study 4 found that squatting produces a prompt increase in cardiac output and arterial blood pressure, which may be related to increased intrathoracic pressure.
- Study 6 discusses the importance of intrathoracic pressure in patients with heart failure, but does not specifically address the effect of squatting on intrathoracic pressure.
Related Haemodynamic Changes
- Squatting has been shown to increase cardiac output, arterial blood pressure, and stroke volume index in both normal individuals and heart transplant recipients 4.
- The haemodynamic responses to squatting are primarily due to augmented venous return and are not altered by cardiac denervation 4.
- Study 5 found that lower body skeletal muscle tensing (LBMT) attenuates the decrease of mean arterial blood pressure (MAP) upon standing from squatting, which may be related to changes in intrathoracic pressure.
Limitations
- The provided studies do not directly measure intrathoracic pressure during squatting, making it difficult to draw conclusions about its effect on intrathoracic pressure 2, 3, 4, 5, 6.
- Further research is needed to fully understand the effect of squatting on intrathoracic pressure and its related haemodynamic changes.