Management of Dropping Oxygen Saturation

Immediate Response Algorithm

The British Thoracic Society recommends targeting oxygen saturation of 94-98% for most patients or 88-92% for those at risk of hypercapnic respiratory failure, and immediately performing a prompt clinical assessment to identify the underlying cause while simultaneously initiating or increasing oxygen therapy 1, 2
The British Thoracic Society suggests checking the pulse oximeter placement and function to ensure the reading is accurate and not due to technical error 3
The British Thoracic Society recommends performing urgent clinical assessment if saturation falls ≥3% or below the patient's target range 1, 4
The British Thoracic Society notes that oxygen treats hypoxaemia, not breathlessness, and that the underlying cause must be diagnosed and treated as a matter of urgency 1, 2

For critically ill patients with SpO2 <85%, the British Thoracic Society recommends administering high-concentration oxygen immediately using a reservoir mask at 15 L/min pending reliable oximetry readings 1, 2, 5
For moderate hypoxaemia (SpO2 85-93%), the British Thoracic Society suggests starting oxygen at 2-6 L/min via nasal cannulae or 5-10 L/min via simple face mask 5
The British Thoracic Society recommends targeting SpO2 of 94-98% for most patients 1, 4, 6
The British Thoracic Society recommends targeting SpO2 of 88-92% for patients at risk of hypercapnic respiratory failure, such as those with COPD, morbid obesity, or neuromuscular disorders 1, 7, 6

The British Thoracic Society recommends reassessing oxygen saturation after 5 minutes of starting or changing oxygen therapy 8, 6
The British Thoracic Society suggests documenting the new saturation, delivery device, and flow rate on the observation chart 8, 3
The British Thoracic Society recommends continuing monitoring, either continuously for critically ill patients or four-hourly for stable patients 8, 6
The British Thoracic Society suggests increasing oxygen concentration if saturation remains below target after verifying correct equipment function 3
The British Thoracic Society recommends using Venturi masks for precise oxygen control in patients requiring specific FiO2, particularly those with COPD 6

The British Thoracic Society recommends targeting 88-92% saturation for patients with COPD, morbid obesity, cystic fibrosis, chest wall deformities, or neuromuscular disorders 1, 7, 6
The British Thoracic Society suggests starting with 24% Venturi mask at 2-3 L/min or 28% Venturi mask at 4 L/min for patients at risk of hypercapnic respiratory failure 7
The British Thoracic Society recommends obtaining repeat blood gas measurements 30-60 minutes after increasing oxygen to ensure CO2 is not rising 3

The British Thoracic Society notes that oxygen improves oxygenation but does not treat the underlying disease, and that the underlying cause must be investigated why saturation dropped 1, 2
The British Thoracic Society recommends assessing for pneumonia, pulmonary embolism, heart failure, pneumothorax, mucus plugging, or equipment malfunction 1

The British Thoracic Society recommends requesting urgent medical review if oxygen requirements increase or saturation remains below target despite appropriate therapy 3
The British Thoracic Society suggests obtaining arterial blood gas for any patient at risk of hypercapnia who requires increased oxygen, or if clinical concern exists despite adequate saturation 3, 6