What is the treatment for respiratory acidosis?

Treatment of Respiratory Acidosis

Bilevel non-invasive ventilation (NIV) is the primary treatment for respiratory acidosis (pH ≤7.35) due to COPD exacerbation or other causes of acute hypercapnic respiratory failure, combined with controlled oxygen therapy targeting SpO2 88-92%. 1

Immediate Management Algorithm

Step 1: Assess Severity and Initiate Oxygen

• Start controlled oxygen therapy immediately using Venturi mask at 24% or nasal cannulae at 1-2 L/min, targeting SpO2 88-92% in COPD patients 2
• Obtain arterial blood gases to confirm respiratory acidosis (pH <7.35, PaCO2 >6.5 kPa) 1
• Avoid excessive oxygen as high concentrations worsen hypercapnia in COPD patients 2

Step 2: Determine NIV Candidacy

For COPD exacerbations with pH ≤7.35:

• Bilevel NIV is strongly recommended and reduces mortality (RR 0.63) and intubation rates (RR 0.41) 1
• NIV should be initiated when pH <7.35, PaCO2 ≥6.5 kPa, and respiratory rate >23 breaths/min persist after one hour of optimal medical therapy 1
• For PaCO2 between 6.0-6.5 kPa, NIV should be considered on a case-by-case basis 1

For neuromuscular disease (NMD) or chest wall deformity (CWD):

• NIV should be trialed in acutely unwell patients with hypercapnia; do not wait for acidosis to develop 1
• Consider NIV when vital capacity is <1 L and respiratory rate >20, even if normocapnic 1

Step 3: NIV Setup and Settings

Initial ventilator parameters: 2

• CPAP: 4-8 cmH2O
• Pressure Support: 10-15 cmH2O
• Backup rate with inspiratory/expiratory ratio of 1:1 for restrictive conditions 1

Implementation considerations: 1

• Explain NIV to the patient before starting
• Select appropriate mask and hold in place initially to familiarize patient
• Secure mask with straps after patient tolerates initial trial
• Add supplemental oxygen if SpO2 <85% 1

Step 4: Concurrent Medical Therapy

Bronchodilators and corticosteroids: 2

• Administer nebulized β-agonist and anticholinergic bronchodilators (can be given during NIV or during brief breaks)
• Start systemic corticosteroids: prednisolone 30 mg/day orally or hydrocortisone 100 mg IV if oral route not possible

Additional therapies: 2

• Antibiotics if signs of infection present
• Consider IV aminophylline 0.5 mg/kg/hour if not responding to initial treatment

Step 5: Monitoring and Reassessment

Early monitoring (first 1-4 hours): 1, 2

• Continuously monitor oxygen saturation, respiratory rate, and level of consciousness
• Repeat arterial blood gases after 30-60 minutes of NIV
• Improvement in pH or respiratory rate within 1-4 hours predicts successful outcome 1
• If pH and PaCO2 deteriorate after 1-2 hours on optimal settings, institute alternative management plan 1

Ongoing management: 2

• Continue NIV for at least 24-48 hours or until clinical improvement
• Monitor for improvement in work of breathing and mental status
• If pH remains <7.25 after initial treatment, continue NIV and consider ICU transfer 2

Escalation to Invasive Mechanical Ventilation

Indications for intubation: 1, 2

• No improvement or worsening after 1-2 hours of optimized NIV
• Life-threatening hypoxemia (PaO2/FiO2 <200 mmHg) despite NIV
• Tachypnea >35 breaths/min despite NIV
• Respiratory arrest or apneic episodes 1
• Psychomotor agitation requiring sedation 1
• Hemodynamic instability (heart rate <60 beats/min, systolic BP <80 mmHg) 1

Important note: There is no lower pH limit below which NIV trial is inappropriate, though lower pH increases failure risk and requires closer monitoring with rapid access to intubation 1

Special Populations

Severe acidosis (pH <7.25): 1

• Bilevel NIV can be used as alternative to first-line intubation in selected patients
• Two studies showed similar mortality with NIV versus invasive ventilation, but NIV had shorter ICU stays and fewer complications when successful 1
• Hypercapnic coma is not a contraindication to NIV trial 1

Patients declining intubation: 1

• Bilevel NIV may be used as the only method of ventilatory support
• Document management plan and patient wishes clearly

Critical Pitfalls to Avoid

Oxygen-related errors: 2

• Never use high-flow oxygen without controlled delivery in COPD patients
• Never abruptly discontinue oxygen therapy as this causes life-threatening rebound hypoxemia
• In hypercapnic COPD patients, PaO2 >10 kPa is associated with acidosis in most cases 3

Electrolyte complications: 4

• Rapid correction of respiratory acidosis can cause life-threatening hypokalemia
• Monitor serum potassium closely, especially with concurrent fluid resuscitation or corticosteroid administration
• Potassium shifts from extracellular to intracellular space as acidosis corrects

Delayed escalation: 1

• One study showed trend toward increased mortality with NIV when escalation to invasive ventilation was delayed
• If no improvement by 4-6 hours, do not continue ineffective NIV

Therapies NOT Recommended

Sodium bicarbonate: 5

• No randomized controlled trials support use for respiratory acidemia
• Potential risks without proven benefit
• Hypercapnic acidosis is well tolerated if tissue perfusion and oxygenation maintained

Doxapram: 6

• Risk of seizures and excessive CNS stimulation
• Can worsen arterial pO2 despite improving alveolar ventilation
• Should be stopped if arterial blood gases deteriorate
• Requires careful monitoring for arrhythmias and blood pressure changes

NIV in non-acidotic hypercapnia: 1

• Conditional recommendation against NIV in COPD patients with hypercapnia but pH >7.35
• Focus should be on medical therapy and controlled oxygen (SpO2 88-92%)

Service Requirements

A typical UK hospital will admit approximately 72 COPD patients per year requiring NIV for respiratory acidosis after initial medical therapy 3. This represents 20% of COPD admissions developing acidosis, with 80% remaining acidotic after initial treatment 3.