What are the appropriate BIPAP settings for an ALS patient with no CO2 retention, who is 5 feet 2 inches tall and weighs 192 pounds?

BIPAP Settings for ALS Patient Without CO2 Retention

For an ALS patient with no CO2 retention who is 5'2" and weighs 192 lbs, the recommended BIPAP settings are IPAP 10-12 cmH2O and EPAP 4-5 cmH2O in spontaneous/timed (ST) mode with a backup rate slightly below the patient's spontaneous respiratory rate.

Mode Selection and Initial Settings

For ALS patients without CO2 retention, the following settings are recommended:

• Mode: Spontaneous/Timed (ST) mode is most appropriate for ALS patients to ensure backup ventilation during periods of respiratory muscle weakness 1
• Initial IPAP: 8-12 cmH2O (start at 10 cmH2O)
• Initial EPAP: 4-5 cmH2O
• Pressure Support (IPAP-EPAP differential): Maintain at least 5-6 cmH2O difference
• Backup Rate: Set slightly below patient's spontaneous respiratory rate
• Target SpO2: 90-94% (without supplemental oxygen if possible)

Titration Strategy

The titration process should follow this algorithm:

1. Begin with the initial settings above

2. Monitor patient comfort, respiratory rate, and SpO2

3. If the patient shows signs of insufficient ventilation:

   • Gradually increase IPAP by 1-2 cmH2O increments to improve ventilation
   • Maximum IPAP typically shouldn't exceed 20 cmH2O in ALS patients without significant lung disease 1, 2
   • Maintain IPAP-EPAP differential of at least 5 cmH2O

4. If the patient develops upper airway obstruction:

   • Increase EPAP by 1-2 cmH2O to maintain airway patency
   • Maximum EPAP typically 5-6 cmH2O in patients without obstructive sleep apnea

Interface Selection

• Mask type: Full face mask is often preferred for ALS patients who may have bulbar involvement
• Custom-fit considerations: Given the patient's height and weight (BMI approximately 35), a properly fitted mask is crucial to prevent leaks and ensure comfort 3
• Alternatives: Consider nasal mask if the patient has good bulbar function and can maintain a lip seal

Monitoring and Follow-up

• Monitor SpO2, respiratory rate, and patient comfort during initial setup
• Perform follow-up within 1-2 weeks to assess:
  • Adherence (aim for >4 hours/night, which has been shown to improve survival) 4
  • Mask fit and comfort
  • Effectiveness of ventilation
  • Need for setting adjustments

Special Considerations for ALS Patients

• ALS patients without CO2 retention still benefit from BIPAP therapy, as it can slow the decline of respiratory function 4
• Regular monitoring is essential as respiratory function may deteriorate rapidly in ALS
• Volume-targeted BIPAP modes may be considered as the disease progresses to maintain consistent tidal volumes 5
• Backup rate becomes increasingly important as respiratory muscle weakness progresses

Common Pitfalls and How to Avoid Them

• Inadequate pressure support: Insufficient pressure support can lead to poor ventilation and patient discomfort
• Excessive pressures: Too high pressures can cause mask leaks, gastric distension, and reduced compliance
• Mask leaks: Ensure proper mask fit and consider custom-fit options if standard masks are problematic 3
• Inadequate humidification: ALS patients often have difficulty managing secretions; adequate humidification is essential
• Failure to adjust settings as disease progresses: Regular reassessment is crucial as respiratory function declines in ALS

BIPAP therapy has been shown to significantly prolong survival and slow the decline of forced vital capacity in ALS patients 4, making appropriate setup and ongoing management critical to improving outcomes in this patient population.