What is the effect of passive range of motion on SvO2 levels?

Passive range of motion exercises can significantly impact stroke volume and, consequently, systemic venous oxygen saturation (SvO2) levels. When passive range of motion is performed, it facilitates venous return by promoting muscle pump activity, which can lead to increased venous blood flow back to the heart. This increase in blood flow can enhance the extraction of oxygen by tissues, thus resulting in a decrease in SvO2 levels.

The assertion that SvO2 can decrease by approximately 18% aligns with physiological principles, as engaging muscles—even passively—can increase metabolic demand and oxygen extraction by peripheral tissues. Understanding this response is crucial, especially in critically ill patients where maintaining appropriate tissue perfusion and oxygenation is vital.

In contrast, the options suggesting no effect or increases in SvO2 levels do not account for the physiological mechanisms that govern oxygen extraction and utilization during passive motion. Instead, they overlook the potential rise in metabolic demand associated with muscle activity, which consequently lowers SvO2.