Our discussion below assumes that physicians have addressed metabolic, inflammatory,
and infectious conditions that may be present and have corrected them to the
extent possible. As soon as the condition that caused respiratory failure has started
to improve, the transition from full ventilatory support to spontaneous breathing
may be initiated. This transition requires sufficient respiratory-muscle strength to
sustain breathing and maintain acceptable gas exchange. In most patients, this
transition also includes the removal of the endotracheal tube. In patients with
prolonged respiratory failure, the term “weaning” may be apropos, since it describes
a gradual process of improving the strength-to-load ratio of the respiratory
system to enable spontaneous respiration. Unfortunately, although this term
is widely used, it is somewhat misleading in the vast majority of patients with
acute respiratory failure. “Liberation” from mechanical ventilation is a better description,
since it implies rapid removal of a burden that is no longer necessary.