Can increasing the backup rate on Bilevel Positive Airway Pressure (BPAP) ST correct hypopneas?

Using Backup Rate to Correct Hypopneas on BPAP ST

Yes, increasing the backup rate on BPAP ST can effectively correct hypopneas, particularly in patients with central hypoventilation, inappropriately low respiratory rates, or those who unreliably trigger IPAP/EPAP cycles due to muscle weakness. 1

Mechanism and Evidence

The backup rate (ST mode) serves several important functions in correcting hypopneas:

• It ensures a minimum number of breaths per minute, preventing prolonged periods of hypoventilation
• It provides machine-triggered breaths when patients fail to initiate breaths on their own
• It helps stabilize breathing patterns in patients with central sleep apnea or mixed events

Research shows that switching from spontaneous (S) mode to spontaneous/timed (ST) mode with an appropriate backup rate significantly reduces respiratory events, particularly those of central and mixed origin 2. In one study of patients with obesity hypoventilation syndrome, changing from ST mode with either high or low backup rate to S mode resulted in a highly significant increase in respiratory events 2.

Backup Rate Adjustment Protocol

When adjusting backup rate to correct hypopneas, follow this algorithm:

1. Initial setting: Set backup rate equal to or slightly less than the patient's spontaneous sleeping respiratory rate, with a minimum of 10 breaths per minute 1

   • If sleeping respiratory rate is unknown, use spontaneous awake respiratory rate

2. Titration: Increase backup rate in 1-2 breaths per minute increments every 10 minutes if hypopneas persist 1

3. Inspiratory time adjustment: Set inspiratory time (IPAP time) based on respiratory rate to provide:

   • 30% of cycle time for patients with obstructive disease (I:E ratio of 1:2.3)
   • 40% of cycle time for patients with restrictive disease (I:E ratio of 1:1.5) 1, 3

4. Calculate appropriate timing: Use these formulas:

   • Cycle time = 60 / respiratory rate (in breaths per minute)
   • Inspiratory time = %IPAP time × cycle time 1

Additional Considerations

If hypopneas persist despite backup rate adjustments:

1. Pressure support adjustment: Consider increasing pressure support (PS) if:

   • Tidal volume remains low (<6-8 mL/kg)
   • SpO2 remains below 90% for 5+ minutes
   • PCO2 remains elevated above goal 1

2. Mode consideration: If ST mode is unsuccessful despite optimal settings, consider switching to timed mode with a fixed respiratory rate 1

3. Supplemental oxygen: Add if SpO2 remains <90% after optimizing PS and respiratory rate 1

Common Pitfalls to Avoid

• Setting backup rate too low: May fail to correct central events or hypopneas
• Setting backup rate too high: May cause patient discomfort, sleep fragmentation, or patient-ventilator asynchrony
• Ignoring inspiratory time: Improper I:E ratio can worsen patient comfort and ventilation efficacy
• Overlooking leaks: Excessive mask leaks can reduce the effectiveness of backup rate adjustments 1

Special Populations

For patients with heart failure and central sleep apnea, flow-targeted dynamic BPAP support with appropriate backup rate has been shown to effectively suppress central sleep apnea-Cheyne Stokes respiration 4, 5. In these patients, BPAP treatment with appropriate backup rates has demonstrated improvements in left ventricular function 5.

For obese patients who fail CPAP therapy, BPAP with appropriate backup rates has shown better adherence and symptom control 6.

Remember that while increasing backup rate is an effective strategy for correcting hypopneas, the overall approach should address the underlying pathophysiology of sleep-disordered breathing for optimal outcomes.