Respiratory Acidosis
pH <7.35, PaCO2 >45. Cause: hypoventilation (alveolar hypoventilation). COPD (most common), opioid overdose, neuromuscular weakness, chest wall disorders, sleep apnea. Compensation: kidneys retain HCO3 (takes 2-3 days for full compensation). Acute: HCO3 rises 1 mEq/L per 10 mmHg PaCO2. Chronic: 4 mEq/L per 10 mmHg.
Respiratory Alkalosis
pH >7.45, PaCO2 <35. Cause: hyperventilation. Anxiety/panic (most common), pain, hypoxia (high altitude, PE, pneumonia), fever, sepsis, salicylates, pregnancy. Compensation: kidneys excrete HCO3 (takes 2-3 days). Acute: HCO3 drops 2 mEq/L per 10 mmHg PaCO2 decrease. Chronic: 5 mEq/L per 10 mmHg.
Nursing Management
Respiratory acidosis: treat underlying cause, improve ventilation (BiPAP, intubation if severe), oxygen if hypoxemic, reversal agents for overdose (naloxone, flumazenil). Respiratory alkalosis: treat anxiety (rebreathing mask, anxiolytics), correct hypoxia, pain control. Monitor ABGs, electrolytes (hypokalemia, hypocalcemia in alkalosis).
Important Notes
- Respiratory acidosis from COPD requires BiPAP or ventilation — do not give high-flow oxygen alone.
- Hypocalcemia in respiratory alkalosis can cause tetany, Chvostek, and Trousseau signs.
Clinical Tips
- Acute respiratory acidosis: HCO3 rises 1 mEq/L per 10 mmHg PaCO2. Chronic: 4 mEq/L.
- Treat respiratory alkalosis by addressing the cause — anxiety, pain, hypoxia.
Summary
Respiratory acid-base disorders require treating the underlying cause (hypoventilation or hyperventilation) and supporting ventilation.
