Received: 28 January 1998 Accepted: 31 March 1998 A. Esteban ( ) ) × I. Alía Servicio de Cuidados Intensivos, Hospital Universitario de Getafe, Carretera de Toledo Km 12,500, E-28 905 Getafe, Madrid, Spain Tel.: + 34 1 6834982 Fax: + 34 1 6832095 Introduction Intubation and mechanical ventilation are routine and life-saving procedures. The percentage of patients re- ceiving ventilatory support in the critical care setting var- ies between 20 % and 60 % according to their clinical characteristics [1±4]. Survival probability in patients who receive mechanical ventilation depends on both the severity of their underlying condition and the extent of complications related to the ventilatory process [5±7]. Endotracheal intubation with mechanical ventilation and the use of ventilatory circuits are the most important risk factors associated with the development of nosoco- mial pneumonia in hospitalized patients. The risk is in- creased several fold for such patients [8±10], and some authors have reported it to increase proportionally to the duration of ventilatory support [11, 12]. Thus, in a prospective study, the actuarial risk of pneumonia in- creased by 1 ± 0.76 % with each day of mechanical venti- lation, being 6.5 % at 10 days, 19 % at 20 days and 28 % at 30 days [11]. The cumulative incidence of pneumonia has been reported as 8.5 % on the first 3 days of ventilation, 21.1 % for day 7, 32.4 % for day 14, and 45.6 % for longer than 14 days [12]. Accordingly, it is crucial to discontinue ventilatory support and extubate at the earliest time that a patient can sustain spontaneous ventilation safely. For the majority of patients, especially those requir- ing short-term respiratory support, mechanical ventila- tion can be removed quickly and easily. However, dis- continuation may be associated with considerable diffi- culty in those recovering from major injuries or acute respiratory failure. These patients account for signifi- cant health care costs and pose a great challenge for cli- nicians, especially as more than 40 % of the time that a patient receives mechanical ventilation is spent in wean- ing [1]. Considering this proportion, it is surprising that guidelines regarding the optimal approach to this pro- cess are so few [13]. Fortunately, several randomized studies carried out in recent years have yielded valuable information in the development of guidelines [14±19]. All have shown that the duration of ventilation and weaning can be reduced by the implementation of spe- cific strategies (Table 1). Failure to wean has been attributed to several mech- anisms, including disturbances in intrapulmonary gas exchange, cardiovascular dysfunction and psychological dependence. The most common cause, however, is an imbalance between the level of ventilation needed by the patient and the ability of their respiratory system to respond. A review of pathophysiological aspects of diffi- cult weaning is beyond the scope of this article, where we attempt principally to discuss the optimal clinical management of weaning. Predictive weaning indexes: what is their role in the decision-making process? Weaning procedures are usually instigated only after the underlying disease process necessitating mechanical ventilation has significantly improved or is resolved. The patient should display adequate gas exchange (P a O 2 > 8 kPa with FIO 2 < 0.50), appropriate neurologi- cal and muscular status and stable cardiovascular func- tion. Once these conditions have been fulfilled, deter- mining the optimal time to discontinue mechanical ven- tilation can be difficult. Some parameters based on re- A. Esteban I. Alía Clinical management of weaning from mechanical ventilation Intensive Care Med (1998) 24: 999±1008 Ó Springer-Verlag 1998 REVIEW