What are the initial ventilator settings for a patient with type 2 respiratory failure?

Initial Ventilator Settings for Type 2 Respiratory Failure

For patients with type 2 respiratory failure, initial ventilator settings should include low tidal volumes of 6-8 ml/kg predicted body weight, respiratory rate of 15-25 breaths/min, IPAP of 10-12 cmH2O (titrated up as needed), EPAP of 5 cmH2O, I:E ratio of 1:1-1:2, and FiO2 titrated to maintain SpO2 of 88-92%. 1, 2

Mode Selection

• Non-invasive ventilation (NIV) using bilevel positive airway pressure (BiPAP) should be the first-line ventilation mode for type 2 respiratory failure when pH <7.35 and PaCO2 >6.0 kPa 1, 2
• For patients with neuromuscular disease or chest wall deformity, use spontaneous/timed (ST) mode with a backup rate to ensure minimum ventilation 1, 2
• If ST mode is unsuccessful, consider timed mode with fixed respiratory rate 1
• For invasive mechanical ventilation, use assist-control or pressure support modes based on patient's ability to trigger breaths 1

Initial Settings for Obstructive Disease (e.g., COPD)

• Tidal volume: 6-8 ml/kg predicted body weight 1, 3
• Respiratory rate: 10-15 breaths/min 1
• I:E ratio: 1:2 to 1:4 (longer expiratory time to prevent air trapping) 1
• PEEP/EPAP: 5 cmH2O (caution with setting PEEP greater than intrinsic PEEP) 1, 2
• FiO2: Titrate to maintain SpO2 88-92% 1, 2
• Target pH: 7.2-7.4 (permissive hypercapnia acceptable) 1

Initial Settings for Neuromuscular Disease & Chest Wall Deformity

• Tidal volume: 6 ml/kg predicted body weight 1
• Respiratory rate: 15-25 breaths/min 1
• I:E ratio: 1:1 to 1:2 1
• PEEP/EPAP: 5-10 cmH2O (higher PEEP may be needed for chest wall disorders) 1, 2
• FiO2: Titrate to maintain SpO2 >92% 1
• Backup rate: Set to equal or slightly less than patient's spontaneous sleeping respiratory rate (minimum 10 bpm) 1

Monitoring and Adjustments

• Check arterial blood gases at 1 hour and 4 hours after initiating ventilation 2, 4
• Adjust settings based on pH, PaCO2, and patient comfort 1, 2
• For NIV, assess response within 1-2 hours to prevent delay in intubation if needed 2, 5
• Target pH >7.20 with improvement in work of breathing 1, 2
• If pH remains <7.25 after 1-2 hours of optimized NIV, consider intubation 2

Special Considerations for COPD

• Avoid excessive oxygen use as it increases risk of respiratory acidosis 1
• Prior to blood gas measurements, use 24% Venturi mask at 2-3 L/min or nasal cannulae at 1-2 L/min 1
• For patients with long-standing hypercapnia (high bicarbonate >28 mmol/L), maintain target SpO2 of 88-92% 1
• Consider Average Volume-Assured Pressure Support (AVAPS) mode for more rapid improvement in pH and PaCO2 5

Indications for Escalation to Invasive Ventilation

• Failure of NIV with worsening respiratory acidosis or increasing oxygen requirements 2
• Decreased level of consciousness 2
• Inability to clear secretions 2
• Severe acidosis (pH <7.25) despite optimized NIV 2

Common Pitfalls to Avoid

• Setting FiO2 too high (>92%) in COPD can worsen hypercapnia 1, 2
• Using excessive PEEP in obstructive diseases can worsen air trapping 1, 2
• Delaying intubation when NIV is failing increases mortality 2
• Inadequate monitoring of arterial blood gases can lead to missed opportunities for ventilator adjustments 2
• Setting tidal volumes >8 ml/kg increases mortality in acute respiratory failure 3, 6
• Failing to set an appropriate backup rate in patients with poor respiratory drive 1, 2

Permissive Hypercapnia Strategy

• Accept pH as low as 7.2 if patient is hemodynamically stable 1
• Avoid rapid correction of chronic hypercapnia, especially with high pre-morbid PaCO2 1
• This strategy reduces barotrauma and improves outcomes 1, 6