What rise time percentage should be set on non‑invasive ventilation (NIV)?

Rise Time Setting on Non-Invasive Ventilation

Adjustable rise time is a desirable feature on NIV ventilators, with shorter rise times generally preferred to reduce inspiratory work load and improve patient-ventilator synchrony, though the optimal setting should be titrated based on patient comfort and underlying pathophysiology.

Understanding Rise Time

Rise time refers to the speed at which the ventilator reaches the target inspiratory pressure (IPAP). This parameter directly affects:

• Patient-ventilator synchrony
• Inspiratory work load
• Patient comfort and tolerance
• Overall effectiveness of ventilation

Evidence-Based Recommendations

General Principles

The BTS guidelines identify adjustable pressure rise time as a "desirable" feature (not essential) for hospital NIV ventilators 1. This classification indicates its importance for optimizing patient comfort and tolerance, though ventilators can function without this adjustment capability.

Short rise times are generally beneficial because they:

• Reduce inspiratory delay time (DT₂)
• Decrease pressure-time product (PTP), which correlates with inspiratory work load
• Improve patient-ventilator synchrony 2

Disease-Specific Considerations

For Obstructive Airway Disease (COPD, Asthma)

• Use shorter rise times (approximately 30% IPAP time)
• Allows adequate expiratory time, which is critical given prolonged expiratory flow limitation
• Prevents air trapping and dynamic hyperinflation
• Particularly important at higher respiratory rates 3

For Restrictive Disease (Neuromuscular, Chest Wall Disorders)

• Use longer rise times (approximately 40% IPAP time)
• Accommodates decreased respiratory system compliance
• Provides adequate inspiratory support despite stiff lungs/chest wall 3

Practical Titration Strategy

Initial Setup

1. Start with manufacturer default settings (typically mid-range)
2. Observe patient response during first 10-30 minutes
3. Monitor for signs of asynchrony:
   • Ineffective triggering
   • Premature or delayed cycling
   • Patient distress or fighting the ventilator

Optimization Algorithm

If patient appears uncomfortable or work of breathing remains high:

• Shorten rise time progressively
• Combine with appropriate triggering sensitivity
• Ensure adequate pressure support level (IPAP 20-30 cm H₂O for acute respiratory failure) 4

If patient experiences:

• Excessive air hunger at breath initiation → Shorten rise time
• Discomfort with rapid pressure delivery → Lengthen rise time slightly
• Persistent asynchrony → Reassess mask fit and leak first, then adjust rise time

Monitoring Effectiveness

The combination of short rise time + high pressure support + sharp triggering sensitivity produces the lowest inspiratory work load for any given patient effort 2. However, this must be balanced against patient tolerance.

Common Pitfalls

1. Ignoring rise time entirely: Many clinicians focus only on IPAP/EPAP levels and neglect rise time, missing an opportunity to optimize synchrony

2. One-size-fits-all approach: Rise time needs differ significantly between obstructive and restrictive pathophysiology

3. Confusing rise time with inspiratory time: These are distinct parameters

   • Rise time = speed to reach target pressure
   • Inspiratory time (Ti) = total duration of inspiration

4. Not reassessing during clinical changes: As patient condition improves or worsens, rise time may need adjustment

5. Excessive leak masking the problem: Poor mask fit can cause apparent asynchrony that won't be fixed by rise time adjustment alone 1

Integration with Other Settings

Rise time adjustment works synergistically with:

• Triggering sensitivity: Sharp triggers + short rise time = minimal work load 2
• Pressure support level: Higher IPAP may require faster rise time to be effective
• Backup rate and Ti: In ST mode, ensure rise time allows adequate pressure delivery within the set Ti 3

Device Variability

Important caveat: Rise time settings are not standardized across ventilator manufacturers 1. What constitutes "fast" on one device may differ on another. Clinicians should familiarize themselves with the specific ventilators used in their institution, and limiting the number of different ventilator models improves staff competency 1.

The sophistication of adjustable rise time requires operator understanding, but when used appropriately, it significantly enhances patient comfort and tolerance—critical factors determining NIV success 1.