Incidence of Ventilator Dyssynchrony in Mechanically Ventilated Patients
Patient-ventilator dyssynchrony occurs in nearly all mechanically ventilated patients at some point during their ICU course, with reported rates ranging from 25% to over 80% depending on the detection method and patient population. 1, 2
Reported Incidence Rates
The incidence of ventilator dyssynchrony varies substantially based on several factors:
Dyssynchrony is documented in more than 40% of patients with dilated cardiomyopathy and QRS greater than 120 milliseconds (though this refers to cardiac dyssynchrony, not ventilator dyssynchrony). 3
In studies using systematic waveform analysis, dyssynchrony indices can reach 100% in certain ventilator settings, particularly when low tidal volumes (6 ml/kg) are used in volume-controlled modes. 4
The median dyssynchrony index was 100% (interquartile range 22-100%) at tidal volumes of 6 ml/kg, and 78% (7-100%) at 7.5 ml/kg in patients with or at risk for ARDS on volume-controlled ventilation. 4
Patient-ventilator dyssynchrony is seen in almost all ventilated patients at any ventilator mode, according to recent clinical reviews. 2
Detection Method Influences Reported Incidence
The wide variation in reported incidence reflects differences in detection methodology:
Waveform analysis is the primary diagnostic tool and must be performed continuously to detect asynchrony patterns, as subtle asynchronies may be undetectable without systematic waveform inspection. 5, 6
The most sensitive detection method involves simultaneous recordings of diaphragm electrical activity and esophageal pressure changes, though this is not routinely available in clinical practice. 6
Visual inspection of pressure and flow waveforms on the ventilator screen can identify seven common forms of dyssynchrony: ineffective triggering, autotriggering, inadequate flow, excessive flow, premature cycling, delayed cycling, and peak pressure apnea. 1
Clinical Context and Risk Factors
Several factors increase the likelihood and severity of dyssynchrony:
Lower tidal volumes during volume-controlled ventilation result in higher patient-ventilator dyssynchrony in most patients with or at risk for ARDS, with severe dyssynchrony indices increasing at each reduction of tidal volume size. 4
Induced baseline flow dyssynchrony (measured by pressure time product > 5 cm H2O/sec) was present in 63% (10 of 16) of stable mechanically ventilated patients when flow was reduced by 50%. 7
Dyssynchrony occurs at any ventilator mode, though the type and severity vary depending on mode selection and ventilator settings. 2, 8
Practical Implications
The high prevalence of dyssynchrony underscores the need for vigilant monitoring:
Every mechanically ventilated patient should have continuous waveform assessment to identify specific asynchrony types, as this allows for systematic ventilator adjustments before resorting to sedation or advanced modes. 5
Checking patient comfort and respiratory rate immediately after any ventilator adjustment, and reassessing waveforms continuously ensures interventions resolve the specific asynchrony type. 5, 6
If not recognized, dyssynchrony may promote oversedation, prolong the duration of mechanical ventilation, create risk for lung injury, and generally confuse the clinical picture. 1