What is the treatment for respiratory acidosis?

Treatment of Respiratory Acidosis

For respiratory acidosis with pH <7.35 and PaCO2 >6.0 kPa, initiate non-invasive ventilation (NIV) if acidosis persists after 30-60 minutes of optimal medical therapy including controlled oxygen targeting 88-92% saturation. 1

Immediate Management: Controlled Oxygen Therapy

Target oxygen saturation of 88-92% in all patients at risk of hypercapnic respiratory failure, not the standard 94-98% target. 1

• Use 24% Venturi mask at 2-3 L/min, nasal cannulae at 1-2 L/min, or 28% Venturi mask at 4 L/min prior to blood gas availability in suspected COPD or other at-risk patients. 1

• Never abruptly discontinue oxygen if excessive oxygen caused the acidosis—this causes life-threatening rebound hypoxemia. Instead, step down to 24-28% Venturi mask or 1-2 L/min nasal cannulae. 1

• Excessive oxygen (PaO2 >10 kPa) significantly increases risk of worsening acidosis in hypercapnic patients. 1

• Controlled oxygen therapy in COPD reduces mortality by 58% overall and 78% in confirmed COPD compared to high-concentration oxygen. 1

Non-Invasive Ventilation (NIV): The Definitive Treatment

When to Start NIV

Initiate NIV when pH <7.35 (H+ >45 nmol/L) with PaCO2 >6.0 kPa persists after 30-60 minutes of optimal medical treatment. 1

• pH 7.25-7.35: Strongest evidence base for NIV benefit—reduces mortality, intubation rates, ICU length of stay, and infectious complications. 1

• pH <7.25: Severe acidosis requiring immediate NIV initiation without waiting for chest X-ray. Consider higher dependency setting (HDU/ICU). 1

• pH >7.35 with hypercapnia but no acidosis: NIV not recommended—focus on medical therapy and controlled oxygen. 1

NIV Settings and Monitoring

• Use bilevel pressure support ventilators as first-line—simpler, cheaper, more flexible than volume-controlled ventilators. 1

• Start with full-face mask initially, changing to nasal mask after 24 hours as patient improves. 1

• Recheck arterial blood gases after 1-2 hours and again at 4-6 hours to assess response. 1

• Improvement in pH or respiratory rate within 1-4 hours predicts successful NIV outcome. 1

• If no improvement in PaCO2 and pH after 4-6 hours despite optimal settings, discontinue NIV and consider invasive mechanical ventilation. 1

• Ventilate for as much time as possible during first 24 hours in patients showing benefit. 1

Location of Care

• pH <7.30 (H+ >50 nmol/L): Manage in HDU or ICU setting. 1

• pH 7.30-7.35: Can initiate on respiratory ward with experienced staff, but transfer to HDU/ICU if no improvement after 1-2 hours. 1

• Patients with conditions where NIV role is uncertain (pneumonia, ARDS, asthma) should only receive NIV in HDU/ICU. 1

Underlying Cause Treatment

Address reversible factors contributing to respiratory failure concurrently with ventilatory support. 1

• Treat bronchospasm, infection, pulmonary edema, pneumothorax, pulmonary embolism as indicated. 1

• Optimize medical therapy including bronchodilators, corticosteroids, antibiotics if appropriate. 1

• Ensure adequate analgesia in chest wall trauma while using CPAP (monitor for pneumothorax in ICU setting). 1

Special Populations

COPD Exacerbations

• 20% develop respiratory acidosis during acute exacerbations. 1, 2
• NIV reduces mortality and intubation rates when pH <7.35. 1, 2
• Approximately 72 patients per year in a typical UK hospital will require NIV for COPD-related acidosis. 2

Neuromuscular Disease and Chest Wall Deformity

• NIV indicated for acute or acute-on-chronic hypercapnic respiratory failure. 1
• Consider NIV-supported extubation rather than tracheostomy when possible. 1
• Refer all patients to home ventilation center for long-term assessment. 1

Obesity Hypoventilation Syndrome

• Use bilevel NIV if respiratory acidosis present, not just CPAP. 1
• Same oxygen saturation targets (88-92%) and NIV criteria apply. 1

Critical Pitfalls to Avoid

• Never use high-flow oxygen in suspected COPD or at-risk patients without blood gas monitoring—this is the most common cause of iatrogenic respiratory acidosis. 1

• Do not delay NIV waiting for chest X-ray when pH <7.25—initiate immediately. 1

• Avoid NIV in patients with excessive secretions (bronchiectasis), severe hemodynamic instability, or inability to protect airway. 1

• Document ceiling of treatment decision before starting NIV—decide whether intubation is appropriate if NIV fails. 1

• Do not continue NIV beyond 4-6 hours without improvement—this delays necessary intubation and worsens outcomes. 1