Which of the following can worsen PaCO2 levels when supplemental oxygen is given?

• A. Increased ventilation
• B. Excessive oxygen concentration
• C. Decreased tidal volume
• D. Correct administration technique

Answer: (B)

The administration of supplemental oxygen can sometimes lead to increased levels of carbon dioxide in the blood (hypercapnia), particularly when excessive concentrations of oxygen are used. This phenomenon is often seen in patients with chronic obstructive pulmonary disease (COPD) or other forms of chronic respiratory failure, where the body has adapted to lower levels of oxygen and relies on a hypoxic drive to stimulate breathing.

When these patients receive high concentrations of supplemental oxygen, it can reduce their respiratory drive, leading to decreased ventilation. This decreased ability to exhale carbon dioxide results in elevated PaCO2 levels. The body’s normal response mechanisms that help regulate carbon dioxide can be altered or inhibited, causing a retention of CO2.

In contrast, increased ventilation should help lower PaCO2 by enhancing carbon dioxide elimination. Decreased tidal volume similarly leads to reduced ventilation, potentially increasing PaCO2 levels, but it isn't the primary factor when considering the impact of supplemental oxygen. Correct administration technique typically aims to deliver oxygen safely and effectively without causing adverse effects, and would not inherently contribute to a worsening of PaCO2 levels when properly executed.

Thus, the concern with supplemental oxygen leading to worsened PaCO2 levels is particularly related to administering excessive oxygen concentrations, which can impair respiratory