Final answer:
An apneic patient will demonstrate a decreased ETCO2 level, as no carbon dioxide is being exhaled. If metabolic acidosis is present, compensation mechanisms may lower PCO2 to keep the bicarbonate balance in check.
Step-by-step explanation:
When a patient is apneic, which means not breathing, you would expect to see a decrease in the end-tidal CO2 (ETCO2) levels. ETCO2 represents the amount of carbon dioxide released at the end of an exhaled breath and is normally used to assess the patient's ventilatory status. Apnea results in no exhalation of CO2, leading to a decline in ETCO2 levels. As the ETCO2 decreases, it might indicate that compensatory mechanisms, such as metabolic acidosis compensation, could occur. During metabolic acidosis, the body attempts to reestablish the normal pH by altering the blood levels of bicarbonate and carbonic acid/CO2. Initially, the partial pressure of carbon dioxide (PCO2) is normal, but with compensation, it may decrease as the body tries to restore the proper bicarbonate balance.