Decreasing level of consciousness or CO2 narcosis - this signals respiratory failure; call for help and prepare to support ventilation.
Before you read
Test yourself first: 5 questions
Question 1 of 5
A client with chronic obstructive pulmonary disease presents with pH 7.34, PaCO2 60 mmHg, HCO3 32 mEq/L. How should the nurse interpret these gases?
Answer: A. The pH is on the acidic side of normal, the PaCO2 is high (respiratory acidosis), and the HCO3 is high (metabolic compensation). Because both buffer systems are abnormal in opposite directions and the pH remains slightly abnormal, this is partially compensated respiratory acidosis, typical of chronic COPD.
Question 2 of 5
A client with chronic obstructive pulmonary disease (COPD) has a pH of 7.33, PaCO2 of 58 mm Hg, and bicarbonate of 30 mEq/L. How should the nurse interpret these gases?
Answer: B. The low pH with high PaCO2 indicates respiratory acidosis. The elevated bicarbonate shows the kidneys are retaining base to compensate, but because the pH is still below normal, the picture is partially compensated respiratory acidosis, typical of chronic CO2 retention in COPD.
Question 3 of 5
The nurse reviews an arterial blood gas: pH 7.30, PaCO2 52 mm Hg, HCO3 24 mEq/L. How should the nurse interpret this result?
Answer: B. A low pH with an elevated PaCO2 and normal bicarbonate indicates uncompensated respiratory acidosis. The bicarbonate has not yet risen to buffer the acidosis.
Question 4 of 5
An opioid overdose has caused severe respiratory depression. Which arterial blood gas pattern does the nurse expect?
Answer: A. Opioid-induced respiratory depression slows ventilation, causing CO2 to accumulate. The result is respiratory acidosis: a low pH with a high PaCO2 and an initially normal bicarbonate. Reversing the cause and supporting ventilation is the treatment.
Question 5 of 5
An ABG shows pH 7.30, PaCO₂ 52, HCO₃ 24. The nurse interprets this as:
Answer: B. Low pH with high CO₂ (opposite directions) = respiratory acidosis. HCO₃ is normal, so it is uncompensated. ROME: Respiratory Opposite.
Keep the streak going with more questions like these, each with a full rationale.
What is respiratory acidosis?
Common causes include any condition that depresses or obstructs breathing: COPD, respiratory depression from opioids/sedation, atelectasis, pneumonia, chest trauma, and neuromuscular disease. CO2 is an acid, so when the lungs cannot exhale it, pH drops. The kidneys compensate over hours to days by retaining bicarbonate.
Key points to remember
- ABG pattern: low pH (under 7.35) with high PaCO2 (over 45 mmHg); the CO2 drives the disorder.
- Renal compensation raises HCO3 over time, especially in chronic respiratory acidosis such as COPD.
- Early signs include tachycardia, dyspnea, restlessness, and hypertension.
- As CO2 rises, the client becomes drowsy, lethargic, and confused, progressing toward CO2 narcosis and coma.
- Hyperkalemia may occur as hydrogen ions shift into cells in exchange for potassium.
- Warm flushed skin and a bounding pulse can result from CO2-induced vasodilation.
Common causes
- COPD, pneumonia, atelectasis
- Opioids, sedation, resp depression
Signs & symptoms
- ↓ LOC, drowsy → coma
- Headache, flushed, ↑ HR
Nursing priorities
- Improve ventilation and gas exchange: position upright, encourage coughing and deep breathing, and provide airway clearance.
- Administer oxygen carefully; in chronic CO2 retainers use low-flow oxygen to avoid suppressing the hypoxic drive.
- Monitor ABGs, oxygen saturation, level of consciousness, and respiratory effort.
- Prepare for bronchodilators, suctioning, or mechanical ventilation/BiPAP as the respiratory status worsens.
- Hold or limit sedatives and opioids that further depress respirations.
Labs & values
Patient teaching
- COPD clients should use prescribed inhalers, do breathing exercises, and avoid respiratory irritants.
- Take sedatives and opioids only as prescribed and never combine with alcohol.
- Report increasing shortness of breath, drowsiness, or confusion.
Red flags: report now
- Decreasing level of consciousness or CO2 narcosis - this signals respiratory failure; call for help and prepare to support ventilation.
- Rising PaCO2 with falling pH despite intervention - notify provider and anticipate intubation/BiPAP.
- Apnea or severe respiratory distress - airway emergency.
References
Clinical references for this topic
