How should acute respiratory failure be managed urgently, including assessment of type, oxygen therapy, non‑invasive ventilation, intubation criteria, and treatment of underlying causes?

Management of Acute Respiratory Failure

Immediately assess the type of respiratory failure (hypoxemic vs. hypercapnic) with arterial blood gas analysis, initiate controlled oxygen therapy targeting SpO₂ 88–92% in hypercapnic patients or 94–98% in hypoxemic patients, and start non-invasive ventilation within 60 minutes if pH <7.35 with PaCO₂ >6.5 kPa persists despite optimal medical treatment. 1, 2

Immediate Assessment and Classification

Determine Respiratory Failure Type

• Obtain arterial blood gas immediately to distinguish Type I (hypoxemic, normal/low PaCO₂) from Type II (hypercapnic, elevated PaCO₂ >6.0 kPa) respiratory failure 3, 2
• Measure respiratory rate, oxygen saturation, blood pressure, and mental status on arrival 1, 4
• Assess for respiratory acidosis: pH <7.35 indicates acute decompensation requiring urgent intervention 5, 2

Risk Stratification by pH

• pH ≥7.30: Manage on respiratory ward with continuous monitoring 1, 2
• pH 7.25–7.30: Strongly consider HDU/ICU admission 1, 2
• pH <7.25: Mandatory HDU/ICU management due to poor NIV response rates 5, 1, 2

Oxygen Therapy Protocol

For Hypercapnic Respiratory Failure (COPD, neuromuscular disease)

• Target SpO₂ 88–92% using 24–28% Venturi mask or 1–2 L/min nasal cannulae 5, 2
• Never give high-flow oxygen without checking for hypercapnia, as this worsens respiratory acidosis and can precipitate life-threatening deterioration 5
• If hypercapnia discovered on supplemental oxygen, step down gradually to 24–28% Venturi—never abruptly stop oxygen, as sudden cessation causes rebound hypoxemia below baseline 5, 2

For Hypoxemic Respiratory Failure (pneumonia, ARDS, pulmonary edema)

• Target SpO₂ 94–98% with conventional oxygen therapy or high-flow nasal oxygen 5, 1
• High-flow nasal oxygen may be superior to conventional NIV for de novo acute hypoxemic respiratory failure with significant mortality reduction 1
• Avoid hyperoxia (PaO₂ >10.0 kPa) even in hypoxemic patients 2

Non-Invasive Ventilation (NIV) Initiation

Indications for Immediate NIV (Grade A Evidence)

Start NIV immediately if all three criteria persist after 60 minutes of optimal medical therapy: 2

• PaCO₂ ≥6.5 kPa (49 mmHg) AND
• pH <7.35 AND
• Respiratory rate >23 breaths/min

Additional NIV Indications

• Acute cardiogenic pulmonary edema with respiratory distress unresponsive to initial medical therapy: use CPAP initially, then PS-PEEP if hypercapnia/acidosis develops 5
• Neuromuscular disease with hypoxemia (SpO₂ <95%), hypercapnia (>6 kPa), elevated respiratory rate, or patient tiring 5
• Consider (not automatic) for PaCO₂ 6.0–6.5 kPa with pH <7.35 2

Absolute Contraindications to NIV

Do not attempt NIV if any of the following present: 5, 1

• Recent facial/upper airway surgery or facial burns/trauma
• Fixed upper airway obstruction
• Active vomiting or recent upper GI surgery
• Inability to protect airway or impaired consciousness
• Copious respiratory secretions that cannot be managed
• Cardiovascular instability or life-threatening hypoxemia requiring immediate intubation

NIV Setup and Initial Settings

Pre-NIV Documentation (Mandatory)

• Document escalation plan with senior staff before starting NIV: specifically whether patient is candidate for intubation if NIV fails 5, 1, 2
• Inform ICU if pH <7.30 or patient at high risk of deterioration 5

Equipment and Interface

• Use full-face mask initially in acute setting, transition to nasal mask after 24 hours as patient improves 1
• Set up bi-level pressure support ventilator with typical initial settings for COPD: IPAP 12–20 cmH₂O, EPAP 4–5 cmH₂O 1, 2
• Add supplemental oxygen to maintain target SpO₂ 88–92% 5, 2

Location of NIV Delivery

• pH 7.30–7.35: Respiratory ward with trained staff and continuous monitoring 1, 2
• pH <7.30: HDU or ICU setting 5, 1, 2
• Patients with pneumonia, ARDS, or asthma (where NIV role less established): only in HDU/ICU with immediate intubation capability 5

Monitoring and Reassessment

Critical Time Points

• Repeat ABG at 1–2 hours after NIV initiation to assess response 5, 1, 2
• If PaCO₂ and pH worsen after 1–2 hours on optimal settings, intubate immediately 5, 2
• If no improvement at 1–2 hours, continue NIV and repeat ABG at 4–6 hours 5, 1
• If no improvement in PaCO₂ and pH by 4–6 hours, proceed to intubation 5, 1, 2

Continuous Monitoring Parameters

• Pulse oximetry, respiratory rate, heart rate, blood pressure 1, 4
• Patient comfort, coordination with ventilator, conscious level 5, 4
• Work of breathing, use of accessory muscles, paradoxical breathing 4

Intubation Criteria

Proceed to Invasive Ventilation If:

• NIV failure: worsening or no improvement in pH/PaCO₂ by 4–6 hours despite optimal settings 5, 1, 2
• Deteriorating mental status or inability to protect airway 5, 6
• Hemodynamic instability or cardiovascular collapse 4, 6
• Persistent severe hypoxemia despite maximal NIV and oxygen 5, 6
• Patient exhaustion or inability to tolerate NIV 5, 4
• Copious secretions preventing effective NIV 5, 1

Special Consideration for Neuromuscular Disease

• In single-organ respiratory failure, prospects of recovery are good and invasive ventilation should be considered when NIV unsuccessful 5
• Extubation should be planned in specialist center with NIV and mechanical insufflator-exsufflator available 5

Treatment of Underlying Causes

Optimize Medical Therapy Before/During NIV

• COPD exacerbation: Bronchodilators (nebulized β-agonists and anticholinergics), systemic corticosteroids 2, 7
• Cardiogenic pulmonary edema: Intravenous diuretics (furosemide 40 mg IV if new-onset, or dose equivalent to oral maintenance), vasodilators if SBP >110 mmHg 5
• Chest infection in neuromuscular disease: Regular physiotherapy with mechanical insufflator-exsufflator 5
• Consider doxapram as respiratory stimulant if pH rises above 7.25 (H⁺ >55 nmol/L) in COPD patients 7

Medications to Use Cautiously

• Avoid routine morphine use in acute heart failure (associated with higher mechanical ventilation rates, ICU admission, and death in ADHERE registry) 5
• Consider low-dose IV morphine (2.5–5 mg) only for severely agitated patients with twitching/tachypnea to improve NIV tolerance 1
• Avoid sympathomimetics/vasopressors except in cardiogenic shock with persistent hypoperfusion 5

Critical Pitfalls to Avoid

Oxygen-Related Errors

• Never abruptly stop oxygen when hypercapnia discovered—causes life-threatening rebound hypoxemia below starting saturation 5, 2
• Never give oxygen alone without checking for hypercapnia in patients with diaphragmatic weakness or neuromuscular disease 5
• Avoid empiric high-flow oxygen without titration to target saturations 5

NIV Management Errors

• Delaying intubation when NIV clearly failing is the most critical error—failure to recognize lack of improvement may result in respiratory arrest 1, 4
• Starting NIV without documented escalation plan and senior discussion 5, 1
• Using NIV in patients with absolute contraindications (impaired consciousness, inability to protect airway, active vomiting) 5, 1
• Inadequate monitoring frequency or monitoring in inappropriate location (ward instead of HDU/ICU for pH <7.30) 1, 2

Service Organization Requirements

• NIV facilities must be available 24 hours/day with trained staff, clear protocols, and respiratory physician oversight 1
• Regular educational sessions needed to ensure on-call medical staff familiar with NIV protocols 5