delayed cycling caused by low trigger and high inspiratory time

• related: basic understanding of ventilators, premature cycling is caused by high trigger sensitivity or low inspiratory time
• tags: #permanent
• source: Murray and Nadel Ch 135 Mechanical Ventilation, Asynchrony Consequences and Management

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• On pressure-time waveform (top), the patient makes active expiratory efforts leading to an increase in the pressure
• The expiratory valve is still closed at this time
• On flow-time graphic (bottom), note that there is no flow for a short time between the end of inspiration and start of expiration (red arrow).
  • Suggests inspiration is shorter than the inspiratory time on the ventilator.
• Delayed cycling occurs when the ventilator’s set inspiratory time exceeds patient’s neural inspiratory time.
• The patient generates active expiratory effort prior to reaching the breath-cycling criterion established by the ventilator. 
• There is no issue initiating the breaths (as occurs in trigger dys-synchrony), nor does the breath end prematurely (as in double trigger)¹

Links to this note

• basic understanding of ventilators
  • delayed cycling caused by low trigger and high inspiratory time

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