How to manage desaturations in patients, particularly those with a history of Chronic Obstructive Pulmonary Disease (COPD) or other respiratory conditions?

Managing Desaturations in Patients

For patients experiencing desaturation, immediately initiate oxygen therapy targeting SpO2 94-98% for most patients, but 88-92% for those with COPD or risk factors for hypercapnic respiratory failure, using controlled delivery devices and checking arterial blood gases within 30-60 minutes to guide further management. 1

Initial Assessment and Oxygen Delivery

Verify Equipment and Patient Factors First

• Confirm the pulse oximeter is correctly placed and functioning normally before assuming true desaturation 1
• Check that the oxygen delivery device and flow rate are correct 1
• If using a cylinder, verify it contains oxygen (check labeling) and is not empty or near-empty 1
• Position fully conscious hypoxaemic patients upright rather than supine, as oxygenation is reduced in the supine position 1

Choose Initial Oxygen Delivery Based on Severity and Risk

For patients WITHOUT COPD or hypercapnic risk:

• If SpO2 <85%: Use reservoir mask at 15 L/min 1
• If SpO2 ≥85%: Use nasal cannulae at 2-6 L/min or simple face mask at 5-10 L/min 1
• Target SpO2 94-98% 1

For patients WITH COPD or hypercapnic risk factors (morbid obesity, cystic fibrosis, chest wall deformities, neuromuscular disorders, bronchiectasis with fixed airflow obstruction):

• Start with 24% Venturi mask at 2-3 L/min, OR 28% Venturi mask at 4 L/min, OR nasal cannulae at 1-2 L/min 1, 2, 3
• Target SpO2 88-92% pending blood gas results 1, 2
• Never target >92% in CO2-retaining patients, as this significantly increases mortality risk 2

Critical Timing for Blood Gas Assessment

• Obtain arterial blood gases within 30-60 minutes of initiating oxygen therapy (or sooner if clinical deterioration) for all patients at risk of hypercapnic respiratory failure 1, 2, 3
• Check that supplemental oxygen achieves PaO2 >8 kPa without unacceptable rise in PaCO2 1
• PaO2 >10 kPa (75 mmHg) indicates excessive oxygen therapy and increases respiratory acidosis risk 2, 3

Management Algorithm Based on Blood Gas Results

If pH and PCO2 are Normal:

• Continue targeting SpO2 94-98% for non-COPD patients 1, 3
• For COPD patients without prior hypercapnic respiratory failure history, may adjust target to 94-98% 1, 3
• For COPD patients with prior hypercapnic respiratory failure, maintain 88-92% target 1, 3

If PCO2 Elevated but pH ≥7.35 (or bicarbonate >28 mmol/L):

• Patient likely has chronic hypercapnia 3
• Maintain target SpO2 88-92% 3
• Continue controlled oxygen delivery 2, 3

If Hypercapnic and Acidotic (pH <7.35):

• Consider non-invasive ventilation (NIV) if respiratory acidosis persists >30 minutes after standard medical management 2
• Maintain SpO2 88-92% target 2
• Never abruptly discontinue oxygen—this causes life-threatening rebound hypoxemia within 1-2 minutes while CO2 remains elevated 2, 3

Adjusting Oxygen Therapy

When to Increase Oxygen:

• If target saturation not achieved, systematically verify equipment function and patient positioning first 1
• For patients with respiratory rate >30 breaths/min, increase Venturi mask flow rates above minimum specified to compensate for increased inspiratory flow 2, 3
• Venturi masks provide more reliable oxygenation than nasal prongs during exercise and acute illness 4

When to Decrease Oxygen:

• Lower oxygen concentration if patient is clinically stable and SpO2 is above target range, or has been in upper zone of target range for 4-8 hours 1
• If target saturation maintained after reduction, continue new delivery system without repeat blood gases if patient stable 1
• Repeat the weaning process gradually 1

Weaning and Discontinuation

Stepwise Approach to Weaning:

• Most stable patients are stepped down to 2 L/min via nasal cannulae prior to cessation 1
• Patients at risk of hypercapnic respiratory failure may require stepping down to 1 L/min (or occasionally 0.5 L/min) via nasal cannulae or 24% Venturi mask at 2 L/min 1
• Stop oxygen once patient is clinically stable on low-concentration oxygen with SpO2 in desired range on two consecutive observations 1

Post-Discontinuation Monitoring:

• Monitor SpO2 on room air for 5 minutes after stopping oxygen 1
• If SpO2 remains in desired range, recheck at 1 hour 1
• Maintain active prescription for target saturation range in case of future deterioration 1

Special Considerations

COPD Patients with Episodic Desaturation:

• Some COPD patients have episodic hypoxaemia during recovery (e.g., intermittent mucus plugging) 1
• Some desaturate when mobilizing despite adequate saturation at rest 1
• Ongoing prescription of target saturation range covers both scenarios 1

Nocturnal Desaturation:

• Approximately 48% of COPD patients on long-term oxygen therapy (LTOT) desaturate during sleep despite adequate daytime oxygenation 5
• Patients with both hypercapnia (PaCO2 ≥45 mmHg) and PaO2 <65 mmHg while breathing oxygen are most likely to desaturate during sleep 5
• Consider increasing oxygen flow by 1 L/min during sleep for COPD patients on LTOT 5

Patients on Established LTOT:

• Taper slowly to usual maintenance oxygen delivery device and flow rate 1
• Senior clinician should consider patient-specific target range if standard range would require inappropriate adjustment of usual oxygen therapy 2, 3
• Do not make decisions about long-term oxygen based on blood gas measurements during acute COPD exacerbations—reassess when stable 1

Common Pitfalls to Avoid

• Excessive oxygen in COPD: 30% of COPD patients receive >35% oxygen in ambulances, and 35% still receive high-concentration oxygen when blood gases are drawn in hospital, contributing to widespread respiratory acidosis 2
• Abrupt oxygen discontinuation in hypercapnic patients: PaO2 plummets within 1-2 minutes while PaCO2 remains elevated, causing potentially fatal hypoxemia 2, 3
• Targeting SpO2 >92% in CO2-retainers: This significantly increases mortality risk through multiple physiological mechanisms 2
• Assuming equipment accuracy: Always verify oximeter function and oxygen delivery system before escalating therapy 1