Answer :
Final answer:
Ventilation affects right heart filling by altering thoracic pressure, thereby influencing venous return and the heart's preload. Inhalation increases and expiration decreases the venous return to the right side of the heart. Sympathetic stimulation and thoracic wall compliance are also factors affecting this process.
Explanation:
Ventilation influences right heart filling by changing the pressures within the thoracic cavity. During inhalation, the diaphragm contracts, leading to an expansion of the thoracic cavity. This decrease in intrathoracic pressure allows the venous return to the heart to increase, contributing to the end-diastolic volume (EDV) and preload of the right ventricle. Conversely, during expiration, the diaphragm relaxes, the thoracic cavity recoils, and the increased intrathoracic pressure can partially restrict venous return, potentially reducing the filling of the right ventricle.
Furthermore, sympathetic stimulation of the venous system enhances venous return, increasing the volume of blood that fills the ventricles, known as ventricular filling. The atria contribute significantly to this filling through the atrial kick, which provides the last portion of blood to the ventricles before contraction. The capacity of the thoracic wall to stretch, known as thoracic wall compliance, also plays a role in how easily the thorax can expand, affecting the overall respiratory effort and indirectly the right heart filling.
