For an infant diagnosed with RDS, what clinical finding on blood gases indicates worsening condition?

In the case of an infant diagnosed with respiratory distress syndrome (RDS), the evaluation of blood gases is crucial for monitoring the condition. A low pH with a high pCO2 indicates a respiratory acidosis, which occurs when there is an accumulation of carbon dioxide due to inadequate respiratory function.

In the context of RDS, this finding suggests that the infant's lungs are not effectively exchanging gases, leading to hypoventilation. As a result, carbon dioxide levels rise in the blood while the pH drops, reflecting a worsening respiratory status. This mechanism is particularly relevant in RDS as it typically originates from surfactant deficiency and can result in the alveoli collapsing, impairing gas exchange.

The other choices do not indicate worsening of the infant’s condition in the same way. For instance, a normal pH with a low pCO2 could suggest respiratory alkalosis or effective compensation, indicating that the infant is still managing to ventilate well. An elevated pH with normal HCO3 may imply that the infant is breathing adequately, whereas a normal pO2 with low HCO3 may point to metabolic compensation without necessarily indicating respiratory failure. Thus, the combination of a low pH and a high pCO2 is the