What is the approach to a patient with desaturation (decreased oxygen saturation)?

Approach to Patient with Desaturation

Immediately initiate oxygen therapy targeting SpO2 94-98% for most patients, or 88-92% for those at risk of hypercapnic respiratory failure (COPD, morbid obesity, cystic fibrosis, neuromuscular disorders), while simultaneously performing rapid clinical assessment to identify the underlying cause. 1, 2

Immediate 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, regardless of COPD status or hypercapnic risk, until the situation stabilizes. 2
• This applies to all patients including those with known COPD—life-threatening hypoxemia takes precedence over hypercapnia concerns initially. 2
• For cardiac arrest or resuscitation scenarios, give the highest possible inspired oxygen during CPR until spontaneous circulation is restored. 1, 2

Moderate Desaturation (SpO2 85-93%)

• Start oxygen at 2-6 L/min via nasal cannulae or 5-10 L/min via simple face mask. 2
• Target SpO2 94-98% for most acutely ill patients without risk factors for hypercapnic respiratory failure. 1, 2
• Target SpO2 88-92% for patients with known COPD, morbid obesity, cystic fibrosis, chest wall deformities, neuromuscular disorders, or bronchiectasis with fixed airflow obstruction. 1, 2

Systematic Clinical Assessment Algorithm

First: Verify Equipment and Measurement Accuracy

• Check pulse oximetry signal quality, proper probe placement, adequate waveform, and correlation with pulse rate. 1, 2
• Verify oxygen delivery system is functioning: check cylinder labeling, ensure cylinder is not empty, confirm correct flow rate and delivery device. 1

Second: Assess for Life-Threatening Causes Requiring Immediate Intervention

• Airway obstruction 2
• Tension pneumothorax 2
• Massive pulmonary embolism 2
• Acute pulmonary edema 2

Third: Comprehensive Vital Signs Assessment

• Measure respiratory rate, heart rate and rhythm, blood pressure, temperature, and mental status. 1, 2
• Calculate physiological track-and-trigger score (e.g., NEWS). 1
• Assess circulating blood volume and presence of anemia. 1

Fourth: Obtain Arterial Blood Gas

• For patients with target saturation 88-92% (at risk of hypercapnic respiratory failure), obtain ABG within 30-60 minutes to ensure carbon dioxide is not rising. 1
• For patients with target saturation 94-98% who are stable, ABG is not required unless there is clinical deterioration or signs of hypercapnia. 1

Monitoring Protocol

Initial Monitoring (First Hour)

• Observe oxygen saturation for at least 5 minutes after starting or adjusting oxygen therapy. 1
• Recheck saturation and vital signs after 1 hour. 1

Ongoing Monitoring Based on Clinical Status

• Critically ill patients (NEWS ≥7): continuous SpO2 monitoring; may require HDU or ICU level care. 1
• Stable patients on oxygen: measure SpO2 and physiological variables four times daily. 1

Oxygen Titration Strategy

When to Increase Oxygen

• If saturation remains below target range after verifying equipment function, increase oxygen according to protocol. 1
• Record new delivery system and flow rate on observation chart after 5 minutes at new concentration. 1
• For patients at risk of hypercapnic respiratory failure, repeat ABG 30-60 minutes after increasing oxygen to ensure CO2 is not rising. 1
• If saturation fails to rise after 5-10 minutes of increased oxygen or there is clinical concern, repeat blood gas measurements. 1

When to Decrease Oxygen

• Lower oxygen concentration if patient is clinically stable and saturation is above target range or has been in upper zone of target range for 4-8 hours. 1
• Repeat blood gases are not required for stable patients requiring reduced oxygen concentration. 1

Weaning and Discontinuation

Gradual Weaning Process

• 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 be stepped down to 1 L/min (or 0.5 L/min) via nasal cannulae or 24% Venturi mask at 2 L/min. 1

Discontinuation Criteria

• Stop oxygen once patient is clinically stable on low-concentration oxygen and saturation is within target range on two consecutive observations. 1
• Monitor SpO2 on room air for 5 minutes after stopping oxygen, then recheck at 1 hour. 1, 3
• If saturation remains satisfactory at 1 hour, oxygen has been safely discontinued, but continue regular monitoring. 1

If Desaturation Recurs After Discontinuation

• Restart oxygen at the lowest concentration that previously maintained target range. 1
• If patient requires higher concentration than before to maintain same target, perform clinical review to establish cause of deterioration. 1

Critical Pitfalls to Avoid

Never Abruptly Discontinue Oxygen in Hypercapnic Patients

• Abrupt oxygen discontinuation causes life-threatening rebound hypoxemia with rapid fall below baseline SpO2. 2
• Instead, step down oxygen gradually to the lowest level required to maintain SpO2 88-92%. 2

Do Not Use Standard Targets for All Patients

• Using 94-98% target for patients with COPD or other hypercapnic risk factors can cause oxygen-induced hypercapnia and respiratory acidosis. 1, 3
• Conversely, accepting 88-92% in patients without hypercapnic risk unnecessarily limits tissue oxygenation. 1

Do Not Delay Clinical Review

• A sudden reduction of ≥3% in oxygen saturation within target range should prompt fuller assessment, as this may be first evidence of acute illness. 1
• If saturation consistently remains below prescribed target despite equipment verification, medical review is mandatory. 1

Special Considerations

Positioning

• Fully conscious hypoxaemic patients should maintain the most upright posture possible, as oxygenation is reduced in supine position. 1
• For pregnant patients, position in full left lateral or use left lateral tilt to avoid aortocaval compression. 2

Acute Coronary Syndrome

• Do not routinely administer oxygen if SpO2 ≥94%, as supplemental oxygen in normoxemic ACS patients increases myocardial injury, infarction size, and arrhythmias. 2
• Only give oxygen if SpO2 <94%, signs of heart failure, shock, or breathlessness are present. 2