What are the initial steps in managing respiratory failure?

Initial Management of Respiratory Failure

The initial management of respiratory failure should begin with assessment of severity through clinical evaluation and arterial blood gas analysis, followed by controlled oxygen therapy targeting saturation of 88-92% for patients at risk of hypercapnic respiratory failure or 94-98% for those without such risk, while simultaneously identifying and treating the underlying cause. 1

Initial Assessment

• Measure oxygen saturation using pulse oximetry, which must be available in all locations where emergency oxygen is used 2
• Check vital signs including respiratory rate, heart rate, and blood pressure to assess severity 2
• Consider arterial blood gas (ABG) measurement for patients with risk factors for hypercapnic respiratory failure 2, 1
• Identify patients at risk of hypercapnic respiratory failure, such as those with COPD, neuromuscular disease, chest wall deformities, or morbid obesity 2, 3
• Obtain chest radiography to identify potential causes or complications, but do not delay treatment in severe cases 1

Oxygen Therapy Administration

For patients without risk of hypercapnic respiratory failure:

• For severe hypoxemia (SpO₂ <85%), start with a reservoir mask at 15 L/min oxygen flow 4
• For less severe hypoxemia (SpO₂ ≥85%), begin with nasal cannulae (1-6 L/min) or a simple face mask (5-10 L/min) 4
• Target oxygen saturation of 94-98% 2, 4

For patients with risk of hypercapnic respiratory failure:

• Target oxygen saturation of 88-92% 3, 1
• Use controlled oxygen therapy via Venturi mask (24-28%) 3, 2
• For patients with COPD without an alert card, start with 24% Venturi mask at 2-3 L/min (or 28% Venturi mask at 4 L/min if 24% mask unavailable) 3
• If saturation remains below 88% in prehospital care despite a 28% Venturi mask, change to nasal cannulae at 2-6 L/min or a simple face mask at 5 L/min 3

Advanced Respiratory Support

High-Flow Nasal Cannula (HFNC):

• Consider HFNC over conventional oxygen therapy for patients with acute hypoxic respiratory failure 4, 5
• HFNC should be the first-line noninvasive respiratory support in patients requiring more than 6 L/min of oxygen or PaO₂/FiO₂ ≤ 200 mm Hg with respiratory rate above 25 breaths/minute 5
• HFNC may result in a modest reduction in hospital-acquired pneumonia compared to conventional oxygen therapy 3
• HFNC may improve patient comfort and dyspnea compared to conventional oxygen therapy 3

Non-Invasive Ventilation (NIV):

• Initiate NIV when pH<7.35 and pCO₂>6.5 kPa persist despite optimal medical therapy 1
• NIV is preferred over invasive ventilation as the initial mode for treating acute respiratory failure in COPD exacerbations, with success rates of 80-85% 1
• For patients with de novo acute respiratory failure, HFNC may be preferable to NIV 6
• NIV remains the first-line oxygenation strategy in postoperative patients and those with acute hypercapnic respiratory failure when pH is equal to or below 7.35 6

Invasive Mechanical Ventilation:

• Consider invasive mechanical ventilation when NIV fails as initial therapy, patient has contraindications to NIV, or risk/benefit analysis favors better outcome with invasive ventilation 1
• For moderate to severe ARDS (PaO₂/FiO₂ <150 mmHg), use higher PEEP, implement prone positioning for >12 hours daily, and provide deep sedative analgesia in the first 48 hours of mechanical ventilation 4

Monitoring and Escalation

• Monitor oxygen saturation continuously for at least 24 hours after initiating treatment 4, 1
• Record oxygen saturation, delivery system, and flow rate on patient monitoring charts 2
• Reassess frequently if breathlessness persists despite normal oxygen saturation 2
• For patients with COPD or other risk factors for hypercapnic respiratory failure, recheck blood gases after 30-60 minutes (or if there is evidence of clinical deterioration) even if the initial PCO₂ measurement was normal 3
• If medium-concentration therapy fails to achieve target saturation, change to a reservoir mask and seek senior or specialist advice 4

Common Pitfalls to Avoid

• Do not administer oxygen without monitoring saturation 2
• Do not target 100% saturation in all patients 2
• Do not delay oxygen therapy in critically ill patients 2
• Do not continue oxygen therapy without reassessment when the patient has stabilized 2
• Avoid sudden cessation of supplemental oxygen as this can cause life-threatening rebound hypoxemia 4
• Be aware that pulse oximetry may be misleading in certain conditions like carbon monoxide poisoning 4
• Do not delay escalation to advanced respiratory support if the patient fails to improve with conventional oxygen therapy 4