Respiratory Failure: Types and Management
Classification of Respiratory Failure
Respiratory failure is fundamentally divided into two types: Type 1 (hypoxemic) with PaO₂ <8 kPa (60 mmHg) and normal or low CO₂, and Type 2 (hypercapnic) with PaCO₂ >6.0 kPa (45 mmHg) often accompanied by hypoxemia. 1
Type 1 Respiratory Failure (Hypoxemic)
- Pathophysiology: Results from ventilation-perfusion (V/Q) mismatch, intrapulmonary shunting where blood bypasses ventilated alveoli entirely, diffusion impairment, or alveolar hypoventilation 2, 1
- Common causes: Acute respiratory distress syndrome (ARDS) with bilateral infiltrates and severe hypoxemia (mortality 30-40%), pneumonia, pulmonary edema from increased vascular permeability or hydrostatic pressures, and pulmonary embolism causing increased dead space 2, 1
- ARDS severity classification: Mild (PaO₂/FiO₂ 200-300 mmHg), moderate (100-200 mmHg), severe (≤100 mmHg) 1
- Key characteristic: Typically responds to supplemental oxygen therapy 1
Type 2 Respiratory Failure (Hypercapnic)
- Pathophysiology: Alveolar hypoventilation is the primary mechanism where minute ventilation is insufficient relative to CO₂ production, with increased airway resistance, dynamic hyperinflation creating intrinsic PEEP (PEEPi), and inspiratory muscle dysfunction 2, 1
- Common causes: COPD exacerbations (majority of Type 2 cases), neuromuscular disorders (ALS, muscular dystrophy, myasthenia gravis), chest wall deformities (scoliosis, thoracoplasty), and obesity hypoventilation syndrome 2, 1
- Critical distinction: Oxygen administration worsens V/Q balance and contributes to PaCO₂ increase—this is why controlled oxygen therapy is essential 1
Management of Type 1 Respiratory Failure
Immediate Oxygen Therapy
Target SpO₂ 94-98% in most patients without risk of hypercapnia using empiric oxygen therapy while diagnostic workup proceeds. 1, 3
High-Flow Nasal Oxygen (HFNO)
- HFNO reduces intubation rates compared to conventional oxygen therapy with significant mortality reduction (absolute risk difference -15.8%). 1, 3
- Provides superior oxygenation, improved patient comfort, decreased aspiration risk, and lesser hemodynamic impact compared to NIV 1
- Consider HFNO before intubation in mild ARDS cases with target SpO₂ >94% 1
Non-Invasive Ventilation (NIV) in Type 1 Failure
- NIV may be attempted only in carefully selected cooperative patients with isolated respiratory failure, no major organ dysfunction, cardiac ischemia, arrhythmias, or secretion clearance limitations. 1
- Critical pitfall: NIV failure is an independent risk factor for mortality in Type 1 failure—delayed intubation in patients who fail to improve on HFNO within 1 hour increases mortality 1, 3
- Predictors of NIV failure: higher severity score, older age, ARDS or pneumonia as etiology, or failure to improve after 1 hour 1
Invasive Mechanical Ventilation
When intubation is required, use lung-protective ventilation with tidal volume 6 mL/kg predicted body weight and plateau pressure <30 cmH₂O. 1, 4
- For mild ARDS (PaO₂/FiO₂ 200-300 mmHg), use low PEEP strategy (<10 cmH₂O) to avoid hemodynamic compromise 1
- Cardiogenic pulmonary edema responds dramatically to diuresis and reduction of preload 1
Management of Type 2 Respiratory Failure
Controlled Oxygen Therapy
Target SpO₂ 88-92% to avoid worsening hypercapnia—this is fundamentally different from Type 1 management. 2, 1
- Administer oxygen through Venturi mask starting at 24% or nasal cannulae at 1-2 L/min 2
- Critical monitoring: Check arterial blood gases at 30-60 minutes to assess for rising PaCO₂ or falling pH 1
- Major pitfall: Administering high-flow oxygen without monitoring CO₂ can precipitate CO₂ narcosis and respiratory arrest 1
Non-Invasive Ventilation (NIV)
Initiate NIV when pH <7.35 and PaCO₂ >6.0 kPa (45 mmHg) after optimal medical therapy—this is the cornerstone of Type 2 management. 2, 1, 3
NIV Implementation Protocol
- Location of care: Patients with pH 7.30-7.35 can be managed on respiratory ward; pH <7.30 requires HDU/ICU 3
- Initial settings: BiPAP mode with IPAP 10-12 cmH₂O and EPAP 5 cmH₂O 1
- Interface: Use full-face mask initially in acute setting, changing to nasal mask after 24 hours as patient improves 3
- Monitoring: Check arterial blood gases at 1-2 hours after initiating NIV, then again at 4-6 hours if earlier sample showed little improvement 2, 3
- Treatment failure criteria: Failure to improve PaCO₂ and pH after 4-6 hours indicates need for intubation 1
NIV Efficacy
- Reduces mortality and intubation rates in COPD exacerbations, with 46% reduction in mortality and 65% reduction in need for intubation 3
- Strongest evidence when pH 7.25-7.35 in COPD population 1
Absolute Contraindications to NIV
- Recent facial or upper airway surgery, facial burns or trauma 3
- Fixed upper airway obstruction 3
- Active vomiting, recent upper gastrointestinal surgery 3
- Inability to protect airway 3
- Copious respiratory secretions 2, 3
- Impaired consciousness, severe hypoxemia 2, 3
Adjunctive Medical Therapy
- COPD exacerbations: Administer systemic corticosteroids, bronchodilators (salbutamol 2.5-5 mg, ipratropium 500 mcg), and antibiotics when bacterial infection suspected 1
- For agitated patients: Consider intravenous morphine 2.5-5 mg to provide symptom relief and improve NIV tolerance 3
- Long-acting inhaled therapies reduce exacerbations by 13-25% in COPD patients 1
Management of Neuromuscular Disease-Related Respiratory Failure
Airway Clearance Techniques
Regular lung volume recruitment (LVR) using handheld resuscitation bag or mouthpiece improves vital capacity, maximum inspiratory capacity, and assisted cough flows. 2
- LVR (breath stacking) is low cost, readily available, and can be taught in a single visit 2
- Manually assisted coughing is more effective when added to volume recruitment 2
Mechanical Insufflation-Exsufflation (MI-E)
For patients with reduced cough effectiveness that cannot be adequately improved with alternative techniques, add regular MI-E (cough assist device). 2
- Beneficial but may require caregiver assistance and may be less effective in patients with bulbar impairment 2
- Associated with high costs—consider based on local resources 2
High-Frequency Chest Wall Oscillation (HFCWO)
- Use HFCWO for secretion mobilization combined with airway clearance therapies such as cough assistance or LVR 2
- Data on use in patients on NIV are limited 2
NIV in Neuromuscular Disease
- NIV is initial treatment of choice during respiratory infections in neuromuscular disease 1
- Pulmonary function testing every 6 months helps guide NIV initiation timing 1
Long-Term Oxygen Therapy (LTOT)
LTOT improves survival in patients with COPD and chronic respiratory failure when PaO₂ ≤7.3 kPa (55 mmHg) during stable 3-4 week period despite optimal therapy. 2
- Flow of 1.5-2.5 L/min through nasal cannulae usually achieves PaO₂ >8.0 kPa (60 mmHg) 2
- Use for minimum 15 hours/day, including during sleep—continuous administration provides greater survival benefit 2
- Assess dosage at least once yearly 2
- Generally not prescribed for patients who continue to smoke 2
Critical Decision-Making Algorithm
Before Initiating Ventilatory Support
Make and document a clear decision about whether the patient is a candidate for endotracheal intubation if NIV fails—verify with senior staff. 3
Type 1 vs Type 2 Differentiation
- Obtain arterial blood gases immediately 3
- If PaO₂ <8 kPa with normal/low CO₂: Type 1—target SpO₂ 94-98%, consider HFNO 1
- If PaCO₂ >6.0 kPa with pH <7.35: Type 2—target SpO₂ 88-92%, initiate NIV 1, 3
Escalation Pathway for Type 2 Failure
- Controlled oxygen (SpO₂ 88-92%) + optimal medical therapy 1
- If pH <7.35 and PaCO₂ >6.0 kPa persists: Start NIV 3
- Reassess at 1-2 hours with arterial blood gases 3
- If no improvement by 4-6 hours: Prepare for intubation 1
Service Organization Requirements
Facilities for NIV must be available 24 hours per day in all hospitals admitting patients with acute respiratory failure, with trained staff, clear protocols, and respiratory physician care. 3