For a patient with type 2 (hypercapnic) respiratory failure, which BiPAP settings— inspiratory time, backup respiratory rate, FiO₂, inspiratory pressure, pressure support above PEEP, and PEEP—are optimal?

BiPAP Settings for Type 2 Respiratory Failure

For acute hypercapnic respiratory failure, start BiPAP with IPAP 15 cmH₂O, EPAP 4-5 cmH₂O, backup rate 12-15 breaths/min, inspiratory time 0.8-1.2 seconds (I:E ratio 1:2 to 1:3), and titrate FiO₂ to maintain SpO₂ 88-92%. 1

Initial Pressure Settings

IPAP (Inspiratory Positive Airway Pressure)

• Start at 15 cmH₂O for most adult patients with type 2 respiratory failure 1
• Increase by ≥1 cmH₂O every 5 minutes based on clinical response 1
• Target tidal volume of 6-8 mL/kg ideal body weight 1
• Maximum IPAP should not exceed 30 cmH₂O in adults ≥12 years 1
• In obese patients with obesity hypoventilation syndrome, IPAP >30 cmH₂O may be required 1

EPAP (Expiratory Positive Airway Pressure)

• Start at 4-5 cmH₂O 1
• In COPD patients with intrinsic PEEP (iPEEP), set EPAP at approximately 75% of measured iPEEP to reduce triggering effort 2
• EPAP >8 cmH₂O is commonly needed in obesity hypoventilation syndrome 1
• Critical warning: Setting EPAP greater than iPEEP can be harmful and worsen gas trapping 1

Pressure Support (IPAP-EPAP differential)

• Minimum differential: 4 cmH₂O 1
• Typical range: 8-12 cmH₂O for adequate ventilation 1
• Maximum differential: 10 cmH₂O 1

Respiratory Rate and Timing

Backup Rate (f bpm)

• Set at 12-15 breaths/min for most patients with type 2 respiratory failure 1
• Use spontaneous/timed (S/T) mode rather than pure spontaneous mode to ensure minimum minute ventilation 1
• In neuromuscular disease, rates of 15-25 breaths/min may be needed 1

Inspiratory Time (Tinsp)

• Target I:E ratio of 1:2 to 1:4 depending on underlying pathology 1
• For COPD/obstructive disease: Use longer expiratory time (I:E ratio 1:3 to 1:4) to allow complete exhalation and prevent gas trapping 1
• For restrictive disease: Use shorter expiratory time (I:E ratio 1:2) to allow adequate inspiratory time 1
• At 12-15 breaths/min with 30-40% IPAP time, inspiratory time should be 0.8-1.6 seconds 1

Oxygen Titration (FiO₂)

Target Saturation

• For type 2 respiratory failure: SpO₂ 88-92% 3, 4
• This target prevents worsening hypercapnia from excessive oxygen 3

Initial Oxygen Flow

• Start at 1 L/min supplemental oxygen 3
• Increase by 1 L/min every 15 minutes until target SpO₂ achieved 3
• Connect oxygen via T-connector at PAP device outlet for optimal mixing 3

Important Technical Consideration

• Higher IPAP/EPAP pressures reduce effective FiO₂ for a given oxygen flow rate due to increased intentional leak 3, 4
• As pressures increase, you may need to increase oxygen flow proportionally to maintain target saturation 3

Titration Algorithm

Upward Titration

1. For apneas: Increase both IPAP and EPAP by ≥1 cmH₂O if ≥2 obstructive apneas occur 1
2. For hypopneas: Increase IPAP by ≥1 cmH₂O if ≥3 hypopneas occur 1
3. For persistent hypercapnia: Increase IPAP to achieve target tidal volume of 6-8 mL/kg 1
4. Wait minimum 5 minutes between pressure adjustments 1

Monitoring Response

• Assess arterial blood gas at 1-2 hours after initiation 3, 4
• Target pH >7.32 initially, with goal of pH >7.35 1, 2
• Permissive hypercapnia (pH >7.2) is acceptable if higher pressures cause discomfort 1
• Monitor for patient-ventilator asynchrony, which indicates need for settings adjustment 1

Common Pitfalls and Solutions

Auto-PEEP in COPD

• COPD patients develop intrinsic PEEP from incomplete exhalation 2, 5
• Solution: Apply external PEEP at 75% of measured iPEEP to reduce work of breathing without worsening hyperinflation 2
• Prolong expiratory time by reducing backup rate or decreasing I:E ratio 1

Treatment-Emergent Central Apneas

• If central apneas develop during titration, decrease IPAP or switch to spontaneous-timed mode with backup rate 1
• This prevents over-ventilation that suppresses respiratory drive 1

Patient Intolerance

• If patient cannot tolerate pressures, restart at lower comfortable pressure 1
• Consider sedation only if absolutely necessary, as it may worsen outcomes 1
• Ensure proper mask fit—full face mask is preferred for mouth breathers 1

Ineffective Triggering

• Manifests as increased work of breathing despite adequate pressures 2
• Solution: Add external PEEP (not exceeding iPEEP) to reduce triggering effort 2
• Consider flow triggering rather than pressure triggering 1

Special Populations

Obesity Hypoventilation Syndrome

• Requires higher pressures: IPAP often >30 cmH₂O, EPAP >8 cmH₂O 1
• Consider volume-assured pressure support modes if high pressures needed 1, 6
• Forced diuresis often necessary as fluid overload contributes to failure 1

Neuromuscular Disease

• Lower pressures adequate (IPAP 10-15 cmH₂O) due to normal lung compliance 1
• May require controlled mode if triggering inadequate 1
• PEEP 5-10 cmH₂O helps maintain lung volume 1

Chest Wall Deformity

• Higher pressures needed (similar to obesity) due to reduced chest wall compliance 1
• PEEP 5-10 cmH₂O commonly required 1

Failure Criteria and Escalation

Signs of NIV Failure

• pH <7.35 with PaCO₂ >6.0 kPa (45 mmHg) despite optimal settings 3
• Worsening mental status or inability to protect airway 3
• Hemodynamic instability 3
• Inability to achieve SpO₂ target despite maximal settings 3, 4

When to Intubate

• Immediate intubation if clinical deterioration despite optimal BiPAP settings 3, 4
• Consider invasive ventilation if no improvement within 1-2 hours 4