When should a patient be given oxygen therapy?

Determining Oxygen Therapy Requirements for Patients

Oxygen therapy should be prescribed to achieve a target saturation of 94-98% for most acutely ill patients or 88-92% for those at risk of hypercapnic respiratory failure, with continuous monitoring to maintain the target range. 1

Initial Assessment for Oxygen Needs

Vital Signs and Clinical Evaluation

• Measure oxygen saturation via pulse oximetry in all breathless and acutely ill patients (the "fifth vital sign")
• Record pulse rate and respiratory rate
• Assess for clinical signs of hypoxemia:
  • Tachypnea
  • Use of accessory muscles
  • Altered mental status
  • Cyanosis
  • Tachycardia

Target Oxygen Saturation Ranges

1. Standard target (94-98%): For most acutely ill patients
2. Conservative target (88-92%): For patients at risk of hypercapnic respiratory failure:
   • COPD patients
   • Neuromuscular disorders
   • Chest wall deformities
   • Cystic fibrosis exacerbations
   • Obesity hypoventilation syndrome

Oxygen Delivery Systems and Initial Flow Rates

For Standard Target Patients (94-98%)

• Nasal cannula: 1-2 L/min for mild hypoxemia (can increase up to 6 L/min)
• Simple face mask: 5-6 L/min for moderate hypoxemia (can increase up to 10 L/min)
• Reservoir mask: 15 L/min for severe hypoxemia 2

For Conservative Target Patients (88-92%)

• Venturi mask: 24-28% oxygen at 2-6 L/min for controlled oxygen delivery
• Nasal cannula: 1-2 L/min with careful titration and monitoring 1

Critical Situations Requiring Immediate High-Flow Oxygen

Apply high-concentration oxygen (reservoir mask at 15 L/min) immediately for:

• Cardiac arrest or resuscitation
• Shock, sepsis, major trauma
• Major head injury
• Carbon monoxide poisoning
• Anaphylaxis

Then titrate down once stable with reliable oximetry readings to maintain target range. 1

Monitoring After Initiating Oxygen Therapy

For All Patients

• Record oxygen saturation and delivery system (including flow rate) on monitoring chart
• Monitor oxygen saturation continuously until patient is stable
• Adjust oxygen delivery to maintain target saturation range

For Patients at Risk of Hypercapnic Respiratory Failure

• Obtain arterial blood gas analysis within 30-60 minutes of starting oxygen therapy
• Repeat blood gas after any significant change in oxygen therapy
• If respiratory acidosis develops due to excessive oxygen therapy, reduce oxygen to maintain 88-92% saturation rather than discontinuing oxygen completely 1, 2

Adjusting Oxygen Therapy

When Saturation Falls Below Target Range

1. Check oxygen delivery system for faults
2. Increase oxygen concentration according to protocol
3. Perform clinical assessment to determine cause of deterioration
4. Consider arterial blood gas if saturation doesn't improve within 5-10 minutes

When Saturation Rises Above Target Range

1. Reduce oxygen concentration
2. Continue monitoring to ensure stability at lower concentration
3. Consider weaning off oxygen if patient maintains target saturation on room air 1

Special Considerations

Pregnancy

• Target 94-98% saturation unless at risk of hypercapnic failure
• Position pregnant women >20 weeks with left lateral tilt to avoid aortocaval compression 1

Palliative Care

• Restrict oxygen use to patients with SpO2 consistently <90% or those reporting significant relief of breathlessness
• For non-hypoxemic patients, try opioids and non-pharmacological measures before oxygen 1

Common Pitfalls to Avoid

• Delayed escalation of care: Early recognition of deterioration and prompt intervention are crucial
• Inappropriate oxygen targets: Using the same target for all patients regardless of risk factors
• Inadequate monitoring: Failing to adjust oxygen therapy based on saturation readings
• Overlooking the underlying cause: Oxygen treats hypoxemia but not the underlying condition 2
• Abrupt discontinuation in hypercapnic patients: Can cause dangerous rebound hypoxemia 1

Key Points to Remember

• Oxygen is a treatment for hypoxemia, not breathlessness
• Supplemental oxygen does not treat underlying causes of hypoxemia
• Prescribe oxygen according to target saturation range and monitor to keep within range
• Adjust oxygen therapy based on saturation readings, not just symptoms
• Document all changes to oxygen therapy on the patient's chart 1