How to calculate BIPAP (Bilevel Positive Airway Pressure) settings?

How to Calculate BiPAP Settings (10/5)

BiPAP settings are calculated based on the pressure differential between inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP), with standard notation showing IPAP/EPAP (e.g., 10/5 means IPAP of 10 cmH2O and EPAP of 5 cmH2O).

Understanding BiPAP Numbers

BiPAP (Bilevel Positive Airway Pressure) settings consist of two primary pressure values:

1. IPAP (Inspiratory Positive Airway Pressure): The higher pressure delivered during inhalation
2. EPAP (Expiratory Positive Airway Pressure): The lower pressure maintained during exhalation

Basic BiPAP Calculation

• When you see BiPAP settings written as "10/5":
  • First number (10) = IPAP in cmH2O
  • Second number (5) = EPAP in cmH2O
  • The pressure differential (IPAP - EPAP) = 5 cmH2O

Starting BiPAP Settings

According to clinical guidelines, initial BiPAP settings should typically be 1, 2:

• Minimum starting IPAP: 8-12 cmH2O
• Minimum starting EPAP: 3-5 cmH2O
• Minimum IPAP-EPAP differential: 4 cmH2O
• Maximum IPAP-EPAP differential: 10 cmH2O

Advanced BiPAP Calculations

For patients requiring ST (Spontaneous-Timed) or Timed modes, additional calculations are needed 1:

Respiratory Rate and Timing Calculations

• Cycle time = 60 / respiratory rate (in breaths per minute)
• Cycle time = (IPAP time + EPAP time)
• I:E ratio = inspiratory time / expiratory time = IPAP time / EPAP time
• %IPAP time = (IPAP time × 100) / (IPAP time + EPAP time)

Recommended I:E Ratios

• Standard %IPAP time: 30-40% of the respiratory cycle 1
• For obstructive disease: Use shorter inspiratory time (%IPAP ≈ 30%)
• For restrictive disease: Use longer inspiratory time (%IPAP ≈ 40%)

Example Calculations

Example 1: Basic BiPAP Setting

• BiPAP 10/5 means:
  • IPAP = 10 cmH2O
  • EPAP = 5 cmH2O
  • Pressure support = 5 cmH2O (10-5)

Example 2: Calculating Timing with Respiratory Rate

For a respiratory rate of 15 breaths/min with 30% IPAP time 1:

• Cycle time = 60/15 = 4 seconds
• IPAP time = 4 × 0.3 = 1.2 seconds
• EPAP time = 4 - 1.2 = 2.8 seconds
• I:E ratio = 1.2/2.8 = 1:2.3

BiPAP Titration Protocol

When adjusting BiPAP settings, follow this algorithm 1, 2:

1. For obstructive apneas: Increase both IPAP and EPAP by 1-2 cmH2O
2. For hypopneas: Increase IPAP by 1-2 cmH2O
3. For RERAs or snoring: Increase IPAP by 1-2 cmH2O
4. For inadequate ventilation/hypercapnia: Increase pressure differential by raising IPAP

Clinical Applications

• COPD exacerbation: Higher IPAP-EPAP differential (often 10+ cmH2O) to overcome airway resistance 2
• Neuromuscular disease: May require higher IPAP (15-20 cmH2O) with backup rate 1, 2
• Obesity hypoventilation: Higher starting pressures (IPAP 15-20, EPAP 8-10) 2
• Acute pulmonary edema: Consider starting at 10/5 cmH2O 1

Common Pitfalls to Avoid

1. Insufficient pressure differential: Ensure at least 4 cmH2O difference between IPAP and EPAP
2. Inadequate EPAP: Too low EPAP may fail to maintain upper airway patency
3. Excessive IPAP: May cause patient discomfort, air leaks, or gastric distension
4. Improper I:E ratio: Incorrect timing can lead to air trapping or inadequate ventilation
5. Ignoring patient synchrony: Adjust settings based on patient comfort and synchrony with the device

Remember that BiPAP settings should be adjusted based on clinical response, including work of breathing, respiratory rate, oxygen saturation, and blood gas results when available.