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Patient-Ventilator Synchrony and Asynchrony — Types and Management

Recognition of common asynchrony patterns (trigger, flow, termination) in mechanically ventilated patients and optimization of settings.

Written by: Saygı Hospital Health Guide Editorial Board
Published: · Last updated:

This content is for general information; please consult your physician for diagnosis and treatment.

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What is Patient-Ventilator Synchrony and Asynchrony — Types and Management?

Patient-ventilator asynchrony (PVA) is a mismatch between the patient's respiratory effort and the ventilator's triggering, flow, or cycling. At least one type of asynchrony is seen in 25-80% of patients, and an asynchrony index (AI = asynchronous breaths / total breaths) >10% is associated with barotrauma and prolonged weaning.

Main types — (1) Ineffective trigger: patient effort fails to trigger a breath (ventilator shows a spike but no delivered breath); (2) Auto-trigger: a breath is triggered without patient effort (water droplet, cardiac oscillation); (3) Double-trigger (breath stacking): continuous patient effort leads to two consecutive breaths; (4) Flow asynchrony: patient demand exceeds delivered flow ('flow starvation'); (5) Cycle asynchrony: ventilator cycles too early or too late.

Causes — inadequate sedation, high respiratory drive (fever, acidosis, pain), low trigger sensitivity, inappropriate mode, auto-PEEP (COPD), inadequate flow, incorrect tidal volume.

Diagnosis — ventilator waveform monitoring (pressure-time, flow-time curves), esophageal pressure (ΔPes for objective muscle effort), electromyography (EMG EAdi in NAVA mode).

Symptoms

Ventilator tracings — missed triggers (patient effort visible but no breath), double breaths (two stacked), premature cycling (short inspiration cut off)
Patient discomfort — agitation, inability to relax despite close monitoring, high sedation requirement
High workload — accessory-muscle use (sternocleidomastoid), paradoxical abdominal motion, diaphoresis
Weaning difficulty — SBT failure, no synchrony even with mode changes
Variability in oxygenation — effects of asynchronous breaths (atelectasis, overinflation)

Risk Factors

High respiratory drive — sepsis, acidosis, pain, fever, hypoxia — spontaneous effort not matched by ventilator
Inadequate sedation — a light-sedation strategy is advantageous but increases asynchrony risk; balance is needed
COPD + auto-PEEP — patient effort cannot exceed intrinsic PEEP to trigger the ventilator
Recovery from NMB — as paralysis wears off, spontaneous breathing may not match the mode
Inappropriate mode (e.g. controlled mode in a patient with preserved respiratory drive)

When to See a Doctor?

If you experience any of the following symptoms, seek medical attention promptly:

  • Asynchrony observed on ventilator screen — review with respiratory therapist/physiotherapist
  • Agitation despite ongoing sedation — investigate asynchrony and adjust mode/settings
  • SBT failure during weaning — differentiate between asynchrony and muscle weakness (ΔPes or EMG EAdi)

Treatment Methods

01
Identify asynchrony type — review ventilator waveforms (pressure-time, flow-time) for 5-10 minutes; calculate AI. Missed triggers are most common; acute double-triggering is most dangerous
02
Trigger sensitivity — pressure trigger of -1 to -2 cmH2O or flow trigger of 2 L/min (more sensitive, lower work). If auto-triggering, reduce sensitivity
03
Flow setting (PCV) / tidal volume (VCV) — increase flow (60-80 L/min) and raise tidal volume for high demand (keeping plateau <30)
04
Mode change — controlled (CMV) → supported (PS, APRV, or NAVA); NAVA (Neurally Adjusted Ventilatory Assist) triggers via diaphragmatic EMG for ideal synchrony
05
Auto-PEEP management (COPD) — increase expiratory time (lower RR, I:E 1:3 to 1:4), external PEEP set to 70-80% of auto-PEEP (to allow triggering)
06
Sedation optimization — in agitation and high effort, use dexmedetomidine (light sedation) or propofol if needed. Fentanyl for pain (high doses cause apnea). NMB as a last resort

Which Department to Visit?

You can visit our Göğüs Hastalıkları department for these complaints. Our specialist physicians will create the most suitable treatment plan for you.

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Health Disclaimer: The information on this page is prepared for general informational purposes only. It does not replace medical diagnosis and treatment. Please consult your physician for your complaints. Saygı Hospital does not accept responsibility for actions taken based on the information on this page.