Management of Acute-on-Chronic Respiratory Acidosis

Diagnosis and Assessment

The British Thoracic Society recommends immediate senior review and consideration for non-invasive ventilation in patients with pH <7.35 and pCO2 >6.0 kPa (45 mmHg) 1
A patient with a venous blood gas demonstrating acute-on-chronic respiratory acidosis (Type 2 respiratory failure) with concurrent hypoxemia requires immediate assessment of respiratory rate, heart rate, and conscious level using AVPU or Glasgow Coma Scale 1
The presence of significant acidemia (pH 7.26), marked hypercapnia (pCO2 65 mmHg), and severe hypoxemia (pO2 42 mmHg and O2 Sat 73%) indicates acute-on-chronic respiratory failure 1, 2

The American Thoracic Society recommends targeting oxygen saturation of 88-92% in patients with hypercapnic respiratory failure, using 24% or 28% Venturi mask or nasal cannulae at 1-2 L/min 1, 3
Higher oxygen targets can worsen hypercapnia and acidosis in patients with hypercapnic respiratory failure 1
The European Respiratory Society suggests increasing Venturi mask flow by up to 50% if respiratory rate >30 breaths/min 3

Non-invasive ventilation (NIV) should be strongly considered in patients with respiratory acidosis (pH 7.26) despite initial treatment, as it reduces mortality and intubation rates in patients with chronic obstructive pulmonary disease (COPD) 1
The American College of Chest Physicians recommends NIV in patients with acute respiratory failure and hypercapnia 1

Continuous pulse oximetry targeting 88-92%, respiratory rate, and conscious level should be monitored in patients with acute-on-chronic respiratory acidosis 1
Repeat blood gases should be checked at 30-60 minutes, or sooner if conscious level deteriorates 1
Investigation into underlying causes, such as COPD exacerbation, pneumonia, pulmonary embolism, neuromuscular disease, or severe obesity, should be conducted while managing the acute respiratory failure 1, 3