What is a common sign of respiratory acidosis on an arterial blood gas test?

A common sign of respiratory acidosis on an arterial blood gas test is a pH less than 7.35. In the context of acid-base balance, respiratory acidosis occurs when there is an accumulation of carbon dioxide (CO2) due to inadequate ventilation. This condition leads to an increase in hydrogen ion concentration in the blood, resulting in a decrease in pH. The normal pH range is typically between 7.35 and 7.45; thus, a pH value lower than 7.35 indicates acidemia, which is consistent with respiratory acidosis.

The other options noted would not indicate respiratory acidosis. A pH greater than 7.45 would suggest alkalosis, while a bicarbonate (HCO3) level less than 22 usually signifies metabolic acidosis rather than respiratory acidosis. Additionally, a partial pressure of oxygen (PaO2) greater than 80 mmHg does not directly correlate with the presence of respiratory acidosis, as it reflects oxygenation status rather than acid-base balance. Therefore, the most relevant indicators of respiratory acidosis on an arterial blood gas test include the presence of a low pH.