By the end of this chapter, the reader should be able to:

1. Understand the concept of patient-ventilator asynchrony

2. Understand its physiological and clinical effects

3. Recognize the types and mechanisms involved

4. Know the main treatment approaches

Concept and general aspects

Patient-ventilator asynchrony is a mismatch between the patient's pattern of breathing concerning the respiratory demands of time, flow, volume and/or pressure, and the ventilator, in relation to the provision of these parameters. Asynchronous events can range from subtle changes, which require high suspicion and advanced monitoring for their detection, to the apparent "fight" between the patient and the ventilator. Patient-ventilator asynchrony has incidence rates from 10% to 85%. This considerable variation relates to different factors interfering both in its incidence and detection since, in daily clinical practice, its identification is not always easy and its detection at the bedside is deficient and greatly underestimated. In most cases, these phenomena are not clinically perceived, mainly if it occurs when the patient is not agitated. Asynchronies may have causes related to the underlying condition of the patient, limitations or problems with the mechanical ventilator and accessories, or both.