Detecting and correcting patient-ventilator asynchronies

Mechanical ventilation (MV) is a life supporting treatment that, unfortunately, can be associated with several complications such as ventilator-induced lung injury, ventilator associated pneumonia or ventilation induced diaphragm dysfunction (VIDD)[1]. Clinicians generally try to provide assisted/supported ventilation instead of fully controlled ventilation in critically ill patients [2]. This strategy aims at avoiding diaphragmatic atrophy [3]. This requires harmonious synchronization and matching with patient’s demands in terms of ventilator needs. Asynchrony between the patient and the ventilator occurs when there is a mismatch between the patient and ventilator in terms of breath delivery timing. Some asynchrony is inevitable because of the mechanical and electrical delays existing within the complex patient-ventilator loop. Gross asynchronies as those where the mismatch between the breath delivery and the patient effort is huge, such as auto-triggering or missing effort. Some asynchronies can cause or be associated with discomfort and dyspnea and/or increased need for sedative and paralytic agents but this is not the case for all of them [4] and asynchronies may even be caused by deeper levels of sedation [5]. This is why a classification based on their mechanism appears useful. A high incidence of asynchrony is associated with prolonged MV and intensive care unit (ICU) length of stay [6,7] and with mortality [8]. Thus, it seems intuitively important to enhance the detection of asynchronies and to adapt the ventilator assistance, although we have no direct evidence that reducing asynchrony improve outcome.