👤 By the CinnaRN Clinical Content Team🕐 Updated 2026-08-23🏷️ Physiological Adaptation🔖 Free to read, print, and share
Also known as: high CO2 · CO2 retention · low pH from lungs · hypoventilation
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Use this quick-reference guide to spot, treat, and prevent Respiratory Acidosis on the NCLEX. Keep it handy during review and on exam day!
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📒 The 1-minute cheat sheet
🧪 Labs
pH < 7.35, PaCO₂ > 45
Kidneys retain HCO₃ (slow)
🩺 Signs
↓ LOC, drowsy → coma
Headache, flushed, ↑ HR
✅ Do
Improve ventilation, O₂, suction
Bronchodilators, position upright
⚠️ Causes
COPD, pneumonia, atelectasis
Opioids, sedation, resp depression
📚 Respiratory Acidosis — full study notes
The cheat sheet above is your quick recall card. These notes go deeper — what it is, what to do first, what must be reported, and what to teach.
Respiratory acidosis is a low blood pH (below 7.35) caused by retained carbon dioxide from inadequate ventilation, reflected in a high PaCO2 (above 45). 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.
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Key points
Understand these first
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.
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Nursing priorities
What to do, in order
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.
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Red flags — report now
Escalate immediately
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.
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Labs & values
Numbers to know
pH normal 7.35-7.45; respiratory acidosis pH less than 7.35
PaCO2 normal 35-45 mmHg; increased (over 45) in respiratory acidosis
HCO3 normal 22-26 mEq/L; increased with renal compensation in chronic cases
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Patient teaching
What patients must know
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.
❓ Respiratory Acidosis: NCLEX FAQs
What are the priority nursing interventions for Respiratory Acidosis?
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.
What are the warning signs of Respiratory Acidosis a nurse must report?
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.
What do I need to know about Respiratory Acidosis for the NCLEX?
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.
What patient teaching is important for Respiratory Acidosis?
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.
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Quick Tip
ABG pattern: low pH (under 7.35) with high PaCO2 (over 45 mmHg); the CO2 drives the disorder.