Question

A 68-year-old female who was admitted with shortness of breath. On your arrival, the patient appears drowsy and is on 10L of oxygen via a mask.

You perform an ABG, which reveals the following results:

• PaO2: 52.5 mmHg
• pH: 7.29
• PaCO2: 68 mmHg
• HCO3–: 26
What does the ABG show:
Oxygenation (PaO2):
pH:
PaCO2:
HCO3–:
Interpretation:

What symptoms or signs are associated with hypercapnia (↑CO2)?

Answer 1

Arterial blood gas (ABG) results from a 68-year-old woman with difficulty breathing show:

• Oxygenation (PaO₂): hypoxemia
• pH: acidosis
• PaCO₂: Hypercapnia
• HCO₃⁻: normal

whose interpretation is: respiratory acidosis.

Hypercapnia can produce symptoms such as confusion, drowsiness or lethargy, headache, nausea and vomiting and, in severe states, can cause severe unconsciousness and coma.

Step-by-step explanation:

Respiratory acidosis is due to a failure in the breathing process that produces hypoventilation, decreasing the partial pressure of oxygen (PaO₂) —hypoxemia— and increasing the partial pressure of CO₂ (PaCO₂), called hypercapnia.

• Acidosis is the result of the accumulation of CO₂ in the body, which is reflected as a decrease in pH below 7.35, with no change in bicarbonate content.
• Hypoxemia is the decrease of PaO₂ below 60 mmHg.
• Hypercapnia is the increase of PaCO₂ in ABG above 45 mmHg.
• Normal bicarbonate (HCO₃⁻) values range from 22 to 28 mEq/L in ABG. This compound can be altered in metabolic acidosis.

Hypercapnia mainly affects the nervous system, producing symptoms that alter the state of consciousness of the affected, also producing headache and even nausea and vomiting.