What is the optimal pulse width for Inspire (Upper Airway Stimulation) therapy?

Pulse Width in Inspire Upper Airway Stimulation Therapy

The optimal pulse width for Inspire Upper Airway Stimulation therapy is typically 90 microseconds, though it may range from 60-120 microseconds depending on individual patient response.

Understanding Pulse Width in Inspire Therapy

Pulse width refers to the duration of each electrical stimulus delivered by the Inspire device to the hypoglossal nerve. This is a critical parameter that affects both the efficacy of upper airway stimulation and patient comfort during therapy.

Key Characteristics of Pulse Width:

• Definition: The time duration of each electrical stimulus pulse
• Typical Range: 60-120 microseconds
• Standard Setting: 90 microseconds for most patients
• Function: Determines how long each electrical stimulus is applied to the hypoglossal nerve

Importance of Pulse Width Settings

Pulse width is one of several programmable parameters in the Inspire system that affects:

1. Effectiveness of tongue protrusion: Longer pulse widths can recruit more motor units in the tongue
2. Battery consumption: Wider pulses use more energy
3. Patient comfort: Wider pulses may cause more sensation or discomfort
4. Therapy outcomes: Directly impacts AHI reduction and oxygen saturation improvement

Optimization Algorithm

When titrating Inspire therapy settings, the following approach to pulse width adjustment is recommended:

1. Initial Setting: Begin with standard 90 microsecond pulse width
2. Assessment: Evaluate therapy response through:
   • Reduction in AHI (target >50% reduction)
   • Improvement in oxygen desaturation index
   • Patient comfort and adherence
3. Adjustment Protocol:
   • If inadequate response with standard voltage: increase pulse width to 100-120 microseconds
   • If patient experiences discomfort: decrease pulse width to 60-80 microseconds
   • If battery life concerns exist: consider lower pulse width settings

Clinical Evidence

Upper airway stimulation has demonstrated significant clinical benefits in multiple studies. The STAR trial showed a 68% decrease in AHI from 29.3 to 9.0 events per hour and a 70% decrease in oxygen desaturation index from 25.4 to 7.4 events per hour at 12 months 1. The ADHERE registry, representing the largest cohort of patients with this therapy, demonstrated a reduction in AHI from 35.6 to 10.2 events per hour 2.

While these studies confirm the overall effectiveness of upper airway stimulation therapy, they don't specifically isolate the optimal pulse width. However, the standard pulse width of 90 microseconds was used in most clinical trials that demonstrated these positive outcomes.

Technical Considerations

When adjusting pulse width, it's important to understand its relationship with other stimulation parameters:

• Voltage and Pulse Width Relationship: Higher voltage with shorter pulse width may achieve similar nerve recruitment as lower voltage with longer pulse width
• Sensing Lead Settings: For optimal therapy, both stimulation parameters (including pulse width) and sensing lead settings should be optimized 3
• Current-Controlled Stimulation: Inspire uses current-controlled stimulation to ensure consistent charge delivery despite changes in impedance 4

Common Pitfalls and Caveats

• Focusing only on voltage: Adjusting only voltage without considering pulse width may miss opportunities for optimization
• Ignoring patient comfort: Excessive pulse width can cause discomfort and reduce adherence
• Battery life considerations: Wider pulse widths consume more battery power
• Overlooking sensing parameters: Recent evidence suggests that optimizing both stimulation settings (including pulse width) and sensing lead settings is more effective than focusing on stimulation settings alone 3

By understanding and appropriately adjusting pulse width as part of the overall Inspire therapy configuration, clinicians can help maximize therapeutic benefit while maintaining patient comfort and device longevity.