How to manage acute desaturations?

Management of Acute Desaturations

Immediately initiate high-flow oxygen at 15 L/min via reservoir mask for any patient with SpO2 <85%, while simultaneously performing rapid clinical assessment to identify and treat the underlying cause. 1

Initial Oxygen Delivery Based on Severity

Critical Desaturation (SpO2 <85%)

• Administer the highest possible inspired oxygen concentration using a reservoir mask at 15 L/min immediately 1
• This applies to all patients regardless of COPD status or hypercapnic risk until the situation stabilizes 1
• For cardiac arrest or resuscitation scenarios, give the highest possible inspired oxygen during CPR until spontaneous circulation is restored 1

Moderate Desaturation (SpO2 85-93%)

• Start oxygen at 2-6 L/min via nasal cannulae or 5-10 L/min via simple face mask 1
• Target SpO2 94-98% for most acutely ill patients 1
• For patients with known COPD, morbid obesity, cystic fibrosis, chest wall deformities, neuromuscular disorders, or bronchiectasis with fixed airflow obstruction, target SpO2 88-92% instead 1

Mild Desaturation (SpO2 94% with ≥3% acute drop)

• A sudden reduction of ≥3% within the target saturation range requires prompt clinical assessment even if the absolute value remains acceptable 1
• Initiate supplemental oxygen to restore SpO2 to baseline target range 1

Immediate Clinical Assessment Algorithm

Step 1: Verify the Reading

• Confirm pulse oximetry signal quality and proper probe placement 1
• Check that the waveform is adequate and correlates with pulse rate 1

Step 2: Assess for Life-Threatening Causes Requiring Immediate Intervention

• Airway obstruction: Check for stridor, inability to speak, use of accessory muscles; may require immediate cricothyroidotomy if complete obstruction 1, 2
• Tension pneumothorax: Assess for absent breath sounds, tracheal deviation, hypotension, distended neck veins 2
• Massive pulmonary embolism: Look for sudden onset, pleuritic chest pain, tachycardia, hypotension 3
• Acute pulmonary edema: Assess for crackles, pink frothy sputum, elevated JVP 3
• Severe bronchospasm: Listen for wheeze, prolonged expiration, silent chest in severe cases 4

Step 3: Record Vital Signs Comprehensively

• Respiratory rate (>30 breaths/min requires immediate escalation regardless of SpO2) 1, 3
• Heart rate and rhythm 3
• Blood pressure 3
• Mental status 3
• Temperature 3

Step 4: Obtain Arterial Blood Gas

• Measure ABG to assess PaO2, PaCO2, pH, and lactate 1
• This is mandatory if oxygen therapy is initiated or increased, particularly in patients at risk of hypercapnic respiratory failure 1
• Repeat blood gases in 30-60 minutes if oxygen therapy continues or clinical deterioration occurs 3

Preoxygenation and Peroxygenation for Intubation

For Patients Requiring Intubation

• Use tight-fitting facemask with circuit capable of delivering CPAP (5-10 cm H2O) if oxygenation is impaired 1
• Apply nasal oxygen at 5 L/min during preoxygenation while awake, then increase to 15 L/min when consciousness is lost 1
• Continue nasal oxygen at 15 L/min or high-flow nasal oxygen (HFNO) at 30-70 L/min during laryngoscopy to provide apneic oxygenation 1, 5, 6

High-Flow Nasal Oxygen (HFNO) Considerations

• HFNO at 60 L/min is superior to standard nasal cannulae at 15 L/min for preventing desaturation during intubation 5
• For patients with severe hypoxemia (PaO2/FiO2 <150), non-invasive positive pressure ventilation (NIPPV) has stronger evidence than HFNO for preventing critical desaturation 1
• HFNO can be maintained during laryngoscopy, providing continuous oxygen flow, whereas NIPPV must be interrupted 1

Management of Hypercapnia from Excessive Oxygen

If Hypercapnic Respiratory Failure Develops

• Never abruptly discontinue oxygen, as this causes life-threatening rebound hypoxemia with rapid fall below baseline SpO2 1
• Step down oxygen to the lowest level required to maintain SpO2 88-92% 1
• Use 24% or 28% Venturi mask, or 1-2 L/min via nasal cannulae depending on blood gas measurements 1
• Obtain repeat ABG to guide further adjustments 1

Oxygen Titration and Monitoring

Adjust Delivery Devices to Maintain Target Range

• Record oxygen delivery device and flow rate on the patient's monitoring chart 1
• Reduce oxygen in stable patients with satisfactory saturation 1
• Discontinue oxygen once the patient maintains saturation within or above target range on room air, but leave the prescription in place for potential deterioration 1

Monitoring Parameters

• Track respiratory rate continuously, as >30 breaths/min requires immediate escalation even with adequate SpO2 1, 3
• Monitor for signs of increased work of breathing: accessory muscle use, nasal flaring, paradoxical breathing 3
• Reassess clinical status if oxygen requirements increase 1

Special Populations

Pregnant Patients (>20 Weeks Gestation)

• Target SpO2 94-98% for major trauma, sepsis, or acute illness during pregnancy 1
• Position in full left lateral position or use left lateral tilt to avoid aortocaval compression 1
• Use manual uterine displacement if reduced consciousness or requiring cardiovascular support 1

Patients with Acute Coronary Syndrome

• Do not routinely administer oxygen if SpO2 ≥94%, as supplemental oxygen in normoxemic ACS patients increases myocardial injury, infarction size, reinfarction rates, and cardiac arrhythmias 1
• Only give oxygen if SpO2 <94%, signs of heart failure, shock, or breathlessness are present 1

Patients Undergoing Endoscopy with Sedation

• Significant desaturation (SpO2 <90% or fall of ≥4% lasting >1 minute) should be corrected with supplemental oxygen targeting 94-98% (or 88-92% if at risk of hypercapnia) 1
• Measure blood gases if prolonged oxygen administration is required, especially in heavily sedated patients with cardiorespiratory comorbidity 1

Common Pitfalls to Avoid

• Never withhold high-flow oxygen in critical illness due to concerns about hypercapnia—initial resuscitation takes priority, with target adjustment based on subsequent blood gas results 1
• Do not rely on normal SpO2 in carbon monoxide poisoning, as pulse oximeters cannot differentiate carboxyhemoglobin from oxyhemoglobin; give maximum oxygen via reservoir mask and check carboxyhemoglobin levels 1
• Avoid sudden oxygen cessation in patients receiving supplemental oxygen, as this causes dangerous rebound hypoxemia 1
• Do not assume desaturation during activities (coughing, eating, defecation) is benign; these episodes indicate inadequate respiratory reserve and require intervention 4
• Ensure jaw thrust is maintained during apneic oxygenation to keep the upper airway patent, as this is critical for effective oxygen delivery 5