Adult CCRN Practice Exam 2026 – Comprehensive Test Preparation Guide

Nutrition status heavily influences immune function in the critically ill. Malnutrition compromises the body's defense by reducing lean body mass and impairs both cell-mediated and humoral immunity—decreasing lymphocyte numbers and activity, weakening phagocytosis, and lowering antibody production. It also weakens the mucosal barrier and alters cytokine signaling, all of which raise the risk of infection and slow healing. In the ICU, the catabolic stress of illness often creates a mismatch between energy/protein needs and intake, making malnutrition a key driver of immunosuppression.

The other factors don’t directly suppress immunity. Excessive hydration isn’t a known mechanism of immune suppression and can lead to edema or electrolyte issues; a stronger gag reflex lowers the risk of aspiration, not immune weakness; a normal skin barrier indicates an intact first line of defense, rather than a compromised immune state.