What is typically a sign of respiratory failure as determined by arterial blood gas analysis?

Elevated PaCO2 is a significant indicator of respiratory failure in arterial blood gas analysis. In respiratory failure, there is an inability of the lungs to adequately exchange oxygen and carbon dioxide. When carbon dioxide (PaCO2) builds up in the bloodstream due to inadequate ventilation or gas exchange, it becomes elevated. This condition often leads to respiratory acidosis, where the pH of the blood decreases as carbon dioxide levels rise, signifying that the respiratory system is failing to function effectively.

Other options do not typically indicate respiratory failure: high pH levels usually suggest alkalosis rather than acidosis, normal HCO3- levels typically indicate that the bicarbonate buffer system is functioning, and a low heart rate may not be directly indicative of respiratory issues but could stem from various other physiological conditions. Thus, an elevated PaCO2 is the primary sign that points toward respiratory failure in the context of arterial blood gas analysis.