What are e-SENS (expiratory sensitivity) and I-SENS (inspiratory sensitivity) on Luna devices?

Understanding e-SENS and I-SENS on Luna Devices

E-SENS (expiratory sensitivity) and I-SENS (inspiratory sensitivity) are critical ventilator trigger settings on Luna devices that determine how the machine detects patient breathing efforts and transitions between inspiratory and expiratory phases, directly impacting patient-ventilator synchrony and work of breathing.

Inspiratory Sensitivity (I-SENS)

I-SENS determines how easily the ventilator detects a patient's inspiratory effort and triggers the delivery of inspiratory pressure support.

• Definition: The threshold of patient effort required to trigger the ventilator to deliver a breath
• Function: Controls how sensitive the ventilator is to a patient's attempt to inhale
• Settings: Usually measured as a flow trigger (in L/min) or pressure trigger (in cmH2O)
• Clinical impact:
  • Too sensitive: May cause auto-triggering (false triggers)
  • Not sensitive enough: Increases work of breathing as patient must generate more effort to trigger the ventilator 1

Expiratory Sensitivity (E-SENS)

E-SENS determines when the ventilator cycles from inspiration to expiration.

• Definition: The point at which the ventilator switches from IPAP to EPAP
• Function: Controls the timing of the transition from inspiration to expiration
• Settings: Usually expressed as a percentage of peak inspiratory flow (e.g., 25% means the ventilator will cycle to expiration when flow decreases to 25% of the peak flow)
• Clinical impact:
  • Too high (e.g., 50%): Causes premature cycling, leading to insufficient inspiratory time and increased patient effort 2
  • Too low (e.g., 1%): Causes delayed cycling, leading to patient-ventilator asynchrony and increased expiratory work 2

Optimal Settings and Adjustments

For E-SENS:

• Optimal setting: Research indicates that 25% of peak inspiratory flow provides the best patient-ventilator synchrony and minimizes work of breathing in COPD patients 2
• Adjustment algorithm:
  1. Start at 25% for most patients
  2. Decrease if patient shows signs of premature cycling (short inspiratory time, increased respiratory rate)
  3. Increase if patient shows signs of delayed cycling (prolonged inspiration, patient fighting exhalation)

For I-SENS:

• Optimal setting: Should be set to be responsive to patient effort while avoiding auto-triggering
• Adjustment algorithm:
  1. Start with manufacturer's default setting
  2. Increase sensitivity (lower numerical value) if patient shows increased work of breathing
  3. Decrease sensitivity if auto-triggering occurs 3

Clinical Significance and Patient Impact

Patient-Ventilator Synchrony

• Proper adjustment of both E-SENS and I-SENS is critical for patient-ventilator synchrony
• Asynchrony can result from:
  • Undetected inspiratory effort
  • Delay in response to inspiration
  • Improper detection of end of breath 1

Work of Breathing

• Optimal E-SENS (25% of peak flow) minimizes total work of breathing, inspiratory work, and expiratory work 2
• Combination of short inspiratory rise time, high pressure support, and optimal trigger sensitivity results in the lowest work of breathing 3

Common Pitfalls and Recommendations

Pitfalls with I-SENS:

• Auto-triggering: Occurs when I-SENS is too sensitive, causing the ventilator to deliver breaths when the patient is not initiating them
• Missed triggers: Occurs when I-SENS is not sensitive enough, causing increased work of breathing

Pitfalls with E-SENS:

• Delayed termination: When E-SENS is set too low (e.g., 1%), causing increased expiratory work and patient discomfort
• Premature termination: When E-SENS is set too high (e.g., 50%), causing insufficient tidal volume and increased inspiratory work 2

Special Considerations:

• For COPD patients: Consider using E-SENS of 25% to optimize synchrony and reduce work of breathing 2
• For patients with restrictive disease: May benefit from longer inspiratory times (lower E-SENS) 1
• For patients with obstructive disease: May benefit from shorter inspiratory times (higher E-SENS) to allow adequate expiratory time 1

Proper adjustment of these settings is essential for optimizing patient comfort, reducing work of breathing, and improving ventilation outcomes, especially in patients with respiratory conditions requiring non-invasive ventilation.