Understanding Triggered Percentage on BiPAP ST
A triggered percentage of 95% on a BiPAP ST machine indicates that the patient is initiating 95% of their breaths spontaneously, while only 5% are being delivered by the machine's backup rate. This is generally considered an excellent clinical indicator that the patient is breathing well on their own with minimal reliance on the machine's timed backup feature.
What Triggered Percentage Means
The triggered percentage specifically refers to:
- Patient-triggered breaths: These are breaths initiated by the patient's own respiratory effort, detected by the machine's sensitivity settings
- Machine-triggered breaths: These are breaths delivered by the machine when the patient fails to initiate a breath within the time window determined by the set backup rate
Clinical Significance
A high triggered percentage (95%) indicates:
- Good respiratory drive
- Appropriate trigger sensitivity settings
- Minimal reliance on the backup rate
- Effective spontaneous breathing capability
Technical Aspects
In BiPAP ST (Spontaneous/Timed) mode:
- The machine provides two pressure levels: IPAP (Inspiratory Positive Airway Pressure) and EPAP (Expiratory Positive Airway Pressure)
- The "ST" designation means the device operates in a spontaneous mode but has a backup rate 1
- If the patient fails to initiate a breath within the time window based on the backup rate, the machine delivers a timed breath 1
Interpreting Triggered Percentage Values
| Triggered % | Clinical Interpretation |
|---|---|
| 95-100% | Excellent - patient is initiating nearly all breaths |
| 80-94% | Good - patient has strong respiratory drive |
| 50-79% | Moderate - patient relies partially on backup rate |
| <50% | Poor - significant reliance on machine-triggered breaths |
Factors That Affect Triggered Percentage
Trigger sensitivity settings:
- Too insensitive: May miss patient effort, resulting in lower triggered percentage
- Too sensitive: May cause auto-triggering, artificially increasing triggered percentage 2
Backup rate setting:
- Setting too high relative to patient's spontaneous rate may decrease triggered percentage
- Optimal setting is typically 2-4 breaths below patient's spontaneous rate 2
Patient factors:
- Respiratory muscle strength
- Level of consciousness
- Medication effects (sedatives, narcotics)
- Underlying disease severity
Optimizing Triggered Percentage
If triggered percentage is lower than desired:
- Adjust trigger sensitivity: Make more sensitive (lower numerical value) to better detect patient effort 2
- Review backup rate: Ensure it's not set too high relative to patient's spontaneous rate
- Check for mask leaks: Excessive leaks can interfere with trigger detection
- Evaluate patient factors: Address any reversible causes of decreased respiratory drive
Common Pitfalls
- Auto-triggering: Can artificially inflate triggered percentage due to machine misinterpreting signals (cardiac oscillations, leaks) as patient effort 2
- Ineffective triggering: Patient may be making efforts that aren't detected, leading to falsely low triggered percentage
- Inappropriate trigger settings: Too sensitive can cause auto-triggering; too insensitive increases work of breathing 2
A triggered percentage of 95% is generally considered optimal, indicating the patient is breathing spontaneously with minimal reliance on the machine's backup rate while maintaining adequate ventilation.