Auto Triggering of the Ventilator
OVERVIEW
- Auto-triggering of the ventilator is inappropriate triggering of ventilation when the patient is not attempting to initiate a breath
- a type of ventilator-patient dyssynchrony
- inspiratory triggers have been made more and more sensitive -> minimised extra-work
CAUSES
Flow distortions caused by:
- cardiogenic oscillations
- high sensitivity settings
- circuit leaks
- endotracheal cuff leaks
- chest tubes
- water condensation in the circuit
-> always consider patient actually breathing!
PRESSURE VERSUS FLOW TRIGGERING
- flow trigger have a theoretical advantage over classical pressure triggers as that patient never has to breath against a closed circuit.
- not documented in studies
ASSESSMENT
Suspect if
- hyperventilating patient (especially if heavily sedated)
- significant air leak via ICC or circuit leak is present
- condensation in the circuit
- triggering matches ECG or SpO2 waveform
Identify cause
- determine if patient truly breathing
-> connect patient to a T-piece with capnograph and look for spontaneous breathing movements and a CO2 waveform - determine if the auto-triggering is due to cardiac oscillations
-> evaluate if the ECG or SPO2 waveform matches triggering - to confirm that auto-triggering is occuring
-> evaluate the Airway Occlusion Pressure at 0.1 second (P.01)
-> if the P.01 is zero and the measured frequency is greater than the set frequency the ventilator is auto-triggering
MANAGEMENT Prevent Auto-triggering
- Minimize leaks
- Remove condensation from the circuit
- Make the trigger threshold less sensitive
VIDEO
K. Scott Richey on Auto-Triggering
References and Links
CCC Ventilation Series
Modes: Adaptive Support Ventilation (ASV), Airway Pressure Release Ventilation (APRV), High Frequency Oscillation Ventilation (HFOV), High Frequency Ventilation (HFV), Modes of ventilation, Non-Invasive Ventilation (NIV), Spontaneous breathing and mechanical ventilation
Conditions: Acute Respiratory Distress Syndrome (ARDS), ARDS Definitions, ARDS Literature Summaries, Asthma, Bronchopleural Fistula, Burns, Oxygenation and Ventilation, COPD, Haemoptysis, Improving Oxygenation in ARDS, NIV and Asthma, NIV and the Critically Ill, Ventilator Induced Lung Injury (VILI), Volutrauma
Strategies: ARDSnet Ventilation, Open lung approach, Oxygen Saturation Targets, Protective Lung Ventilation, Recruitment manoeuvres in ARDS, Sedation pauses, Selective Lung Ventilation
Adjuncts: Adjunctive Respiratory Therapies, ECMO Overview, Heliox, Neuromuscular blockade in ARDS, Prone positioning and Mechanical Ventilation
Situations: Cuff leak, Difficulty weaning, High Airway Pressures, Post-Intubation Care, Post-intubation hypoxia
Troubleshooting: Autotriggering of the ventilator, High airway and alveolar pressures / pressure alarm, Ventilator Dyssynchrony
Investigation / Indices: A-a gradient, Capnography and waveforms, Electrical Impedance Tomography, Indices that predict difficult weaning, PaO2/FiO2 Ratio (PF), Transpulmonary pressure (TPP)
Extubation: Cuff Leak Test, Extubation Assessment in ED, Extubation Assessment in ICU, NIV for weaning, Post-Extubation Stridor, Spontaneous breathing trial, Unplanned extubation, Weaning from mechanical ventilation
Core Knowledge: Basics of Mechanical Ventilation, Driving Pressure, Dynamic pressure-volume loops, flow versus time graph, flow volume loops, Indications and complications, Intrinsic PEEP (autoPEEP), Oxygen Haemoglobin Dissociation Curve, Positive End Expiratory Pressure (PEEP), Pulmonary Mechanics, Pressure Vs Time Graph, Pressure vs Volume Loop, Setting up a ventilator, Ventilator waveform analysis, Volume vs time graph
Equipment: Capnography and CO2 Detector, Heat and Moisture Exchanger (HME), Ideal helicopter ventilator, Wet Circuit
MISC: Sedation in ICU, Ventilation literature summaries
- K. Scott Richey — Ventilator Waveform of the Week: Auto-triggering
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
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