What is the management of respiratory acidosis?

Management of Respiratory Acidosis

The cornerstone of managing respiratory acidosis is non-invasive ventilation (NIV) initiated when pH <7.35 with PaCO2 ≥6.5 kPa persists after one hour of optimal medical therapy, combined with controlled oxygen therapy targeting SpO2 88-92%. 1, 2

Immediate Assessment and Stabilization

Identify Severity Through Blood Gas Analysis

• Obtain arterial blood gases immediately to confirm respiratory acidosis (pH <7.35, PaCO2 >6.5 kPa) and distinguish from metabolic acidosis 1, 2
• Measure respiratory rate—rates >23 breaths/min combined with acidosis indicate need for NIV 1
• Assess mental status changes, as altered consciousness signals severe hypercapnic acidosis requiring urgent intervention 2
• Check bicarbonate levels >28 mmol/L, which suggests chronic compensated respiratory failure rather than acute decompensation 2

Initiate Controlled Oxygen Therapy

• Target oxygen saturation of 88-92% using Venturi mask at 24% or nasal cannula at 1-2 L/min to avoid worsening hypercapnia 1, 2, 3
• Never provide excessive oxygen (PaO2 >10.0 kPa), as this worsens respiratory acidosis in hypercapnic patients 2, 4
• Use air-driven nebulizers rather than oxygen-driven systems when administering bronchodilators 2

Non-Invasive Ventilation Protocol

Indications for NIV

• Start NIV when pH <7.35, PaCO2 ≥6.5 kPa, and RR >23 breaths/min persist after 60 minutes of optimal medical therapy 1
• For PaCO2 between 6.0-6.5 kPa, consider NIV based on clinical context 1
• In neuromuscular disease or chest wall deformity, initiate NIV with any hypercapnia in acutely unwell patients—do not wait for acidosis to develop 1

NIV Settings and Implementation

• Begin with bilevel positive airway pressure: CPAP 4-8 cmH2O and pressure support 10-15 cmH2O 3
• For COPD patients, use modest pressure support (8-12 cmH2O difference) 1
• For severe kyphoscoliosis, higher IPAP (20-30 cmH2O) may be required due to high chest wall impedance 1
• Continue NIV for as much of the first 24-48 hours as possible, with breaks only for medications, meals, and physiotherapy 1, 3

Monitoring NIV Response

• Recheck arterial blood gases after 1-2 hours of NIV to assess improvement in pH and PaCO2 1, 2
• If no improvement in pH and PaCO2 after 4-6 hours despite optimal settings, discontinue NIV and consider invasive mechanical ventilation 1
• Continuously monitor oxygen saturation, respiratory rate, heart rate, and level of consciousness 1, 2, 3
• Monitor ECG if pulse rate >120 bpm, dysrhythmia present, or known cardiomyopathy 1

Medical Management

Treat Underlying Causes

• Administer nebulized bronchodilators (β-agonist and anticholinergic) for COPD or asthma exacerbations 3
• Start systemic corticosteroids: prednisolone 30 mg/day orally or hydrocortisone 100 mg IV if oral route unavailable 3
• Prescribe antibiotics if clinical signs of infection are present 3
• Consider IV aminophylline 0.5 mg/kg/hour if inadequate response to initial bronchodilator therapy 3

Adjunctive Therapies

• Ensure adequate airway clearance with physiotherapy, particularly in neuromuscular disease and chest wall disorders 1
• Maintain hydration and nutrition, especially critical in cystic fibrosis patients 1
• Sodium bicarbonate is NOT indicated for respiratory acidosis—it increases plasma bicarbonate but does not address the underlying ventilatory problem and may worsen hypercapnia 5

Location of Care and Monitoring Intensity

Triage Based on Severity

• Patients with pH <7.30 should be managed in HDU/ICU regardless of underlying cause 1
• Those showing no improvement after 1-2 hours of NIV on a respiratory ward require transfer to HDU/ICU 1
• Patients with AHRF from pneumonia, ARDS, or asthma should receive NIV only in HDU/ICU where immediate intubation is available 1

Contraindications and Adverse Features

• Respiratory arrest or peri-arrest are relative contraindications—a brief NIV trial by experienced operators can be attempted while preparing for intubation 1
• Adverse features (severe acidosis, impaired consciousness, copious secretions, hemodynamic instability) increase NIV failure risk and mandate HDU/ICU placement 1
• Bulbar dysfunction in neuromuscular disease requires higher EPAP and special attention to airway clearance 1

Escalation to Invasive Mechanical Ventilation

Indications for Intubation

• No improvement or worsening after 1-2 hours of optimized NIV 3
• Life-threatening hypoxemia (PaO2/FiO2 <200 mmHg) despite NIV 3
• Tachypnea >35 breaths/min persisting despite NIV 3
• Worsening mental status, inability to protect airway, or hemodynamic instability 2

Critical Pitfalls to Avoid

Oxygen Management Errors

• Never abruptly discontinue oxygen therapy in hypercapnic patients—this causes life-threatening rebound hypoxemia 2, 3
• Avoid high-flow oxygen concentrations that worsen hypercapnia and acidosis 2, 3
• Do not rely solely on pulse oximetry—arterial blood gases are essential for management decisions 2

Timing and Decision-Making Errors

• Do not delay NIV initiation while waiting for further deterioration 1
• pH is a better predictor of survival than PaCO2 alone during acute episodes 2
• In neuromuscular disease with vital capacity <1 L and RR >20, consider NIV even if normocapnic 1

Special Populations

Neuromuscular Disease and Chest Wall Disorders

• Use controlled ventilation mode (PCV) as triggering may be ineffective 1
• Lower pressure support (8-12 cmH2O) typically sufficient unless severe skeletal deformity present 1
• Refer all patients with spinal cord lesions, neuromuscular disease, chest wall deformity, or morbid obesity who develop AHRF for long-term home ventilation assessment 1

Chronic Home Ventilation Users

• Set patient-specific target saturation ranges based on baseline values 2
• Modest increases in domiciliary ventilator settings usually sufficient during acute illness 1
• Early specialist involvement essential for optimal management 2