Oxygen Therapy and Blood Gas Analysis

Introduction to Oxygen Therapy

The British Thoracic Society recommends that patients with low oxygen levels (SpO₂ < 85%) should start with an initial oxygen therapy of 15 L/min using a reservoir mask 3
For patients with chronic obstructive pulmonary disease (COPD) or at risk of hypercapnia, the target oxygen saturation should be set at 88-92% using a 24% or 28% Venturi mask 4, 5
For patients without hypercapnia risk, the target oxygen saturation should be set at 94-98% 6, 3

Patients with respiratory acidosis (pH < 7.35, PCO₂ > 6.0 kPa) should be considered for non-invasive ventilation (NIV) and respiratory stimulants like doxapram 2

The British Thoracic Society recommends monitoring oxygen saturation, respiratory rate, heart rate, blood pressure, and mental status at least twice a day after starting oxygen therapy 3
For patients with a respiratory rate exceeding 30 breaths/min, the Venturi mask flow rate can be increased by up to 50% 1, 7
After changing oxygen therapy, blood gas analysis should be re-examined 1 hour later (or sooner if the patient's condition worsens) 2, 6

In patients with cystic fibrosis, the target oxygen saturation should be set at 88-92%, similar to COPD, and managed according to regional CF specialist center protocols 1, 5
For patients with paracetamol or bleomycin poisoning, oxygen should only be administered if oxygen saturation falls below 85%, and reduced or discontinued if it exceeds 88% 5
Patients with neuromuscular diseases or chest wall deformities may require NIV or mechanical ventilatory support, and early blood gas analysis is necessary 7, 5

Even with normal pulse oximetry, blood gas analysis may be necessary based on clinical condition, as pH abnormalities, PCO₂ abnormalities, or anemia may be present 1
Excessive oxygen therapy can increase the risk of respiratory acidosis in COPD patients, and PaO₂ should not exceed 10.0 kPa 8
Abrupt cessation of oxygen therapy can lead to life-threatening rebound hypoxemia, and should be tapered gradually 8