Final answer:
Adding 10 cm H2O PEEP can decrease blood pressure by increasing intrathoracic pressure, which reduces venous return and cardiac output, leading to decreased MAP and potential ischemia or hypoxia if not properly managed.
Step-by-step explanation:
When you add 10 cm H2O Positive End-Expiratory Pressure (PEEP) to mechanical ventilation, it can result in a decline in blood pressure from a normal range of 120/80 mm Hg to 90/60 mm Hg. The rationale behind this is that the increased intrathoracic pressure exerted by PEEP can impede venous return to the heart, thus decreasing the preload, which can lead to a reduced cardiac output and subsequent fall in blood pressure. Additionally, high levels of PEEP can compress intrathoracic vessels, further diminishing venous return and affecting the mean arterial pressure (MAP). Normally, MAP falls within the range of 70-110 mm Hg, and maintaining this is crucial for adequate tissue perfusion and oxygenation. If MAP falls below 60 mm Hg, it may result in ischemia or hypoxia, which can severely affect organ function, particularly in sensitive tissues like neurons. The pressure changes when PEEP is applied is an example of the physiological balance between respiratory settings and cardiovascular stability which needs to be carefully monitored in clinical settings.