Pressure-support ventilation (PSV) is a mode of partial ventilator support. Such modes are widely used in intensive care units (ICUs) because most ventilated patients (unless deeply sedated) have preserved respiratory drive. The use of these modes helps to reduce need for sedation, an important issue in the ICU,1,2 and potentially prevents disuse atrophy of the respiratory muscles that can result from controlled ventilation.3,4 This preventive effect has been shown experimentally with different modes of partial support.3,5 Finally, partial support may facilitate both the screening process for detecting patients able to breathe spontaneously as well as the weaning of patients with prolonged or difficult weaning.6 An ideal mode of partial support should be able to supply both full ventilator support and optimal support during weaning; optimize patient–ventilator synchronization and comfort while reducing the need for sedation and the risk of cardiovascular consequences; and, if possible, facilitate or reduce the duration of the weaning. PSV meets several of these requirements, at least partially, as discussed in this chapter. PSV also has limitations, which are delineated. One important limitation is that overassistance of the patient can be easily reached and improvement in the delivery of the optimal PSV level continues as a field of research.
PSV can be remarkably effective in reducing patient effort and avoiding respiratory distress, and can offer a comfortable ventilator support to many patients. PSV can also deliver support much in excess of patient needs and results in excessive delivered volume, excessive duration of inspiration relative to neural inspiratory time (TI), or both. Much recent research has been undertaken to understand and analyze the consequences of delivering of excessive pressure. Many benefits of PSV, which provides greater freedom to the patient than traditional modes, can be obscured by improper usage.
Some clinicians view PSV primarily as a mode devoted to weaning and only consider its use until late in a patient’s course.6 An international survey on mechanical ventilation in 361 ICUs in twenty countries was conducted in 1998 (published in 2002).7 On the first day, PSV was used in less than 10% of all patients; the combination of SIMV with PSV was used in almost 15%, and assist-control in approximately 60% of the patients. A low level of PSV was used to perform a once-daily weaning attempt in 28% of such attempts, a gradual reduction of PSV was used as the sole weaning method in 21% of cases, and a gradual reduction of synchronized intermittent mandatory ventilation (SIMV) and PSV was used in 22% of all cases. Overall, PSV was used (one way or another) for 45% of weaning attempts, suggesting that clinicians consider weaning as the main indication for PSV.
In 2004, Esteban et al repeated the prospective international observational cohort study, employing a nested comparative study performed in 349 intensive care units in twenty-three countries, and compared the findings with the ...