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Promoting Patient-Ventilator Synchrony

Thille, Arnaud W. MD; Brochard, Laurent MD

doi: 10.1097/CPM.0b013e31815b1234
Critical Care/Respiratory Care
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Patient-ventilator asynchrony, in which the patient's inspiration fails to coincide exactly with the ventilator's insufflation, is common in clinical practice. Studies suggest that nearly one-fourth of intubated patients exhibit frequent asynchrony during assisted ventilation. Frequent asynchrony is associated with longer duration of mechanical ventilation, because it may reflect not only greater disease severity, but also inappropriate ventilator settings. New-generation ventilators with large screens facilitate the detection of gross asynchronies by careful examination of flow and airway-pressure tracings. The main asynchrony is ineffective triggering, defined as failure of a patient's inspiratory effort to trigger a ventilator breath. Ineffective triggering is caused by dynamic hyperinflation at the time of a triggering attempt. Other major asynchronies include double triggering, in which 2 consecutive ventilator cycles are triggered by a single patient effort; and auto-triggering, in which the ventilator is triggered by signals that do not come from the patient. More discreet asynchronies such as prolonged insufflation during pressure-support ventilation or inadequate flow rate during assist-control ventilation can also be suspected from the flow and airway-pressure traces. Simple delays in triggering or cycling are extremely common but difficult to detect. Optimizing the ventilator settings, most notably by reducing ventilatory support or insufflation time, can minimize ineffective triggering. New ventilatory modes such as proportional-assist ventilation and neurally adjusted ventilatory assist may improve patient-ventilator synchrony. Whether optimizing ventilation shortens the duration of mechanical ventilation by reducing the occurrence of asynchrony is still an open question.

Patient-ventilator asynchrony is common during assisted ventilation and is associated with longer duration of mechanical ventilation. Ineffective triggering with wasted efforts is the most common type of asynchrony. Once detected, it can be minimized or eliminated by optimizing the ventilator settings.

From the Medical Intensive Care Unit, AP-HP, Henri Mondor Hospital, University of Paris XII, INSERM U651, Créteil, France.

Address correspondence to: Arnaud W. Thille, MD, Service de Réanimation Médicale, Hôpital Henri Mondor, 51 avenue du Maréchal de Lattre de Tassigny, 94010 Créteil, France. E-mail: arnaud.thille@wanadoo.fr.

© 2007 Lippincott Williams & Wilkins, Inc.