Understanding Patient-Ventilator Asynchrony
People display normal variability in their breathing patterns even at rest. In contrast, although a necessary medical intervention, mechanical ventilation uses some sort of fixed parameter in almost all currently available modes. If the mechanical breath is delivered in a fashion that the patient doesn’t want or expect (too short, not enough flow, too long, etc.), asynchrony between the ventilator and the patient, discomfort, anxiety, and fatigue can result.14
Different types of asynchrony occur at different rates and may elicit different patient effects.15 Studies evaluating the overall frequency of asynchronies found that 12-43% of patients exhibit asynchrony in greater than 10% of total breaths.16,17 In these patients, improving patient-ventilator synchrony may potentially result in less anxiety and need for sedation.1
In patients undergoing pressure-support ventilation (PSV), a high number of asynchronous breaths is associated with an almost fivefold increase in ICU mortality,16 a greater than threefold increase in median duration of mechanical ventilation, and a greater than twofold increase in median hospital length of stay.18 Prolonged mechanical ventilation (≥ 21 days) has been shown to be associated with a 23% increase in daily average cost per patient and a 3.3 times higher hospital cost, while also accounting for a disproportionate consumption of healthcare resources.19