What happens to intrathoracic pressure when squeezing a bag-valve-mask during ventilation?

When squeezing a bag-valve-mask (BVM) during ventilation, the mechanism involved creates an increase in both airway pressure and intrathoracic pressure. This occurs as a result of the positive pressure generated by the bag.

As the bag is compressed, it forces air into the patient's lungs through the mask, which leads to a rise in airway pressure. This is necessary to open the airway and allow for the effective movement of air into the lungs. Additionally, because the chest cavity is a closed system and the lungs expand due to the influx of air, the intrathoracic pressure also increases. This increase in intrathoracic pressure can impact venous return to the heart and intrapleural pressure, although the primary focus here is on how both pressures rise with effective BVM ventilation.

Understanding this principle is essential for effective ventilation strategies and ensuring that adequate air exchange occurs during resuscitation efforts or in patients who are unable to breathe adequately on their own.