How to manage a patient with tachypnoea and hypoxemia (low oxygen saturation)?

Management of Tachypnoea with Hypoxemia (SpO₂ 85%)

Immediately start oxygen therapy with a reservoir mask at 15 L/min to target SpO₂ 94-98% for most patients or 88-92% for patients at risk of hypercapnic respiratory failure. 1, 2

Initial Assessment and Management

1. Oxygen Therapy Initiation:

   • For SpO₂ <85%: Start with reservoir mask at 15 L/min 1
   • For patients with known COPD or risk of hypercapnic respiratory failure: Use Venturi mask (24-28%) or nasal cannula at 1-2 L/min to target SpO₂ 88-92% 1, 2

2. Immediate Investigations:

   • Obtain arterial blood gases (ABGs) while initiating oxygen therapy
   • Monitor vital signs closely (respiratory rate, heart rate, blood pressure)
   • Continuous oxygen saturation monitoring 2

3. Assessment for Hypercapnic Respiratory Failure:

   • If pH <7.35 or [H+] >45 nmol/L and PCO₂ >6.0 kPa: Consider respiratory acidosis
   • Seek immediate senior review and consider NIV or invasive ventilation 1

Escalation of Respiratory Support

If SpO₂ remains below target despite initial oxygen therapy:

1. Escalation pathway:

   • Nasal cannula (1-2 L/min) → increase up to 6 L/min
   • Simple mask (5 L/min) → increase up to 10 L/min
   • Reservoir mask at 15 L/min → maintain and seek specialized help 2

2. Consider Non-Invasive Ventilation (NIV) if:

   • Hypercapnic respiratory failure (pH 7.25-7.35)
   • Persistent dyspnea despite controlled oxygen therapy
   • Increased work of breathing 2
   • Initial NIV settings: inspiratory pressure 17-35 cmH₂O and expiratory pressure 7 cmH₂O 2

3. Consider Invasive Mechanical Ventilation if:

   • NIV fails
   • Severe acidosis (pH <7.25)
   • Altered mental status
   • Hemodynamic instability 2

Special Considerations

For patients with COPD or risk of hypercapnic respiratory failure:

• Target SpO₂ 88-92% to prevent oxygen-induced hypercapnia 1, 3
• Risk factors for hypercapnia include: COPD, morbid obesity, asthma, cystic fibrosis, chest wall deformities, bronchiectasis, and neuromuscular disorders 3
• Monitor for signs of CO₂ retention: drowsiness, headache, flushed skin, bounding pulse

For severe hypoxemia despite standard oxygen therapy:

• Consider advanced respiratory support techniques:
  • Prone positioning for ARDS patients with PaO₂/FiO₂ ratio ≤100 mmHg 2
  • Consider PEEP to avoid alveolar collapse 2

Common Pitfalls to Avoid

1. Uncontrolled oxygen administration in patients at risk of hypercapnic respiratory failure can worsen respiratory acidosis 3

2. Inadequate monitoring of oxygen therapy - ensure proper flow rates and delivery system integrity 4

3. Delayed escalation of respiratory support when initial oxygen therapy is insufficient

4. Failure to identify and treat underlying cause of hypoxemia and tachypnea (pneumonia, pulmonary edema, COPD exacerbation) 2

5. Ignoring the need for adjunctive therapy - bronchodilators, antibiotics, corticosteroids as indicated by underlying cause 2

Remember that tachypnea and tachycardia are more common signs of hypoxemia than visible cyanosis 1. Careful monitoring of respiratory rate and heart rate is essential for early detection of deterioration.