What is the management of respiratory acidosis?

Management of Respiratory Acidosis

Non-invasive ventilation (NIV) should be started when pH <7.35, a PaCO2 of ≥6.5 kPa (>45 mmHg) and respiratory rate >23 breaths/min persists or develops after an hour of optimal medical therapy. 1

Initial Assessment and Management

• Obtain arterial blood gases to confirm respiratory acidosis (pH <7.35, PCO2 >45 mmHg) and assess severity 1, 2
• Chest radiography is recommended but should not delay treatment in severe acidosis 1
• Target oxygen saturation of 88-92% using controlled oxygen therapy to avoid worsening hypercapnia 1, 2
• Identify and treat underlying causes of respiratory failure (e.g., COPD exacerbation, neuromuscular disorders, drug overdose) 2, 3

Ventilatory Support Decision Algorithm

Step 1: Optimal Medical Therapy (First Hour)

• Administer controlled oxygen therapy targeting 88-92% saturation 1, 2
• Use air-driven nebulizers rather than oxygen-driven when bronchodilators are needed 2
• Treat underlying causes with appropriate medications 2

Step 2: Reassess After 1 Hour of Optimal Medical Therapy

• If pH <7.35, PaCO2 ≥6.5 kPa (>45 mmHg), and respiratory rate >23 breaths/min persist: Initiate NIV 1
• For patients with PaCO2 between 6.0-6.5 kPa: Consider NIV 1

Step 3: Location of NIV Treatment Based on Severity

• Severe acidosis (pH <7.25): Provide NIV in HDU or ICU setting 1
• Moderate acidosis (pH 7.25-7.35): NIV can be provided in a respiratory ward with appropriate monitoring 1
• Patients with pneumonia, ARDS, or asthma: Only provide NIV in HDU or ICU where immediate intubation is available 1

NIV Protocol

1. Document management plan if NIV fails, after discussion with senior medical staff 1
2. Determine appropriate location for NIV (ICU, HDU, or respiratory ward) 1
3. Consider informing ICU team 1
4. Explain NIV to the patient 1
5. Select appropriate mask and familiarize patient 1
6. Set up ventilator with appropriate initial settings 1
7. Monitor with pulse oximetry 1
8. Reassess clinical status and arterial blood gases at 1-2 hours 1

Monitoring Response to NIV

• Improvement in physiological parameters (particularly pH and respiratory rate) within 1-2 hours predicts successful outcome 1
• If no improvement or deterioration in pH and PaCO2 after 1-2 hours on optimal NIV settings, consider alternative management plan 1
• If no improvement after 4-6 hours, institute alternative management plan (usually intubation and mechanical ventilation) 1

Special Considerations

• Advanced age alone is not a contraindication to NIV 1
• Severe acidosis alone does not preclude a trial of NIV in an appropriate setting with access to staff who can perform endotracheal intubation 1
• NIV should not delay escalation to invasive mechanical ventilation when appropriate 1
• Monitor potassium levels closely when rapidly correcting respiratory acidosis, as life-threatening hypokalemia can develop 4
• Sodium bicarbonate therapy for respiratory acidosis is controversial and generally not recommended as there is lack of evidence for benefit and potential risks 5

Common Pitfalls to Avoid

• Excessive oxygen therapy (PaO2 >10.0 kPa) can worsen respiratory acidosis 2
• Abrupt discontinuation of oxygen therapy can cause rebound hypoxemia 2
• Continued use of NIV when the patient is deteriorating, rather than escalating to invasive mechanical ventilation, increases mortality 1
• Relying solely on PCO2 levels rather than pH to guide management decisions 2

Staffing Considerations

• NIV can be successfully set up and maintained by trained ICU staff, doctors, physiotherapists, lung function technicians, and nurses 1
• Clear protocols should be available for on-call medical staff regarding indications for NIV, initiation of treatment, and ongoing responsibility 1
• All patients started on NIV should be transferred to the care of a respiratory physician as soon as possible 1