Should a patient be started on fixed BiPAP (Bilevel Positive Airway Pressure) or auto BiPAP?

Fixed vs Auto BiPAP: Selection for Patients with Sleep Apnea

For most patients requiring BiPAP therapy, fixed BiPAP should be initiated first rather than auto BiPAP, as there is insufficient evidence supporting the superiority of auto BiPAP over fixed BiPAP for clinical outcomes including mortality, morbidity, and quality of life. 1

Indications for BiPAP vs CPAP

Before deciding between fixed and auto BiPAP, it's important to understand when BiPAP is indicated over standard CPAP therapy:

• BiPAP should be reserved for specific clinical scenarios, as CPAP or APAP remains first-line therapy for most OSA patients 2
• Consider BiPAP when:
  • Patient requires PAP pressures >20 cm H₂O 2
  • Patient is intolerant of high CPAP pressures (typically >15 cm H₂O) 1
  • Patient has continued obstructive respiratory events at 15 cm H₂O of CPAP 1
  • Patient has demonstrated non-acceptance of CPAP after adequate trial 2
  • Patient has respiratory conditions requiring different inspiratory and expiratory pressures (e.g., chronic hypoventilation syndromes) 2

Fixed BiPAP vs Auto BiPAP

When BiPAP is indicated, the evidence supports starting with fixed BiPAP:

• There is insufficient high-quality evidence comparing auto-trilevel or auto-bilevel PAP to fixed BiPAP for most patients 1
• The American College of Physicians guideline does not specifically recommend auto BiPAP over fixed BiPAP 1
• Initial settings for fixed BiPAP should include:
  • IPAP starting at 8 cm H₂O
  • EPAP starting at 4 cm H₂O
  • Minimum IPAP-EPAP differential of 4 cm H₂O
  • Maximum IPAP-EPAP differential of 10 cm H₂O 1

Titration Protocol for Fixed BiPAP

When initiating fixed BiPAP, follow this evidence-based titration protocol:

1. Start with IPAP 8 cm H₂O and EPAP 4 cm H₂O 1, 2
2. Increase IPAP and/or EPAP by at least 1 cm H₂O with intervals no shorter than 5 minutes 1
3. For obstructive apneas: Increase both IPAP and EPAP 1
4. For hypopneas, RERAs, or snoring: Increase primarily IPAP 1
5. Continue titration until respiratory events are eliminated or maximum recommended pressures are reached (IPAP 30 cm H₂O for adults) 1
6. If treatment-emergent central apneas occur, consider decreasing IPAP or setting BiPAP in spontaneous-timed mode with backup rate 1

Special Considerations

While fixed BiPAP is generally the first choice, there are specific situations where auto BiPAP might be considered:

• For patients with obesity hypoventilation syndrome (OHS) with concurrent moderate or severe OSA, some evidence suggests auto-trilevel PAP might be more effective at correcting hypercapnia and improving sleep quality than fixed BiPAP 3
• For patients with variable pressure needs throughout the night, auto-adjusting technology might theoretically provide better comfort, though clinical outcome benefits are not well-established

Potential Pitfalls and Caveats

• Setting the IPAP-EPAP differential too narrow (<4 cm H₂O) may not provide adequate ventilatory support 1
• Setting the IPAP-EPAP differential too wide (>10 cm H₂O) may cause patient discomfort 1
• If the patient awakens complaining of excessive pressure, restart at a lower pressure that allows return to sleep 1
• BiPAP carries risk of increased work of breathing in some COPD patients compared to pressure support ventilation 4
• Ensure proper mask fit and patient education to optimize adherence regardless of mode selected 2

In conclusion, while auto BiPAP technology exists, the current evidence supports initiating therapy with fixed BiPAP for most patients requiring bilevel therapy, with careful titration to achieve optimal pressure settings based on elimination of respiratory events and patient comfort.