Page 552 - Clinical Application of Mechanical Ventilation

518 Chapter 16

Weaning Success

Weaning success is defined as absence of ventilatory support 48 hours following
weaning success: Absence of
ventilatory support 48 hours the extubation (Boles et al., 2007). While the spontaneous breaths are unassisted
following the extubation. by mechanical ventilation, supplemental oxygen, bronchodilators, pressure support
ventilation, or continuous positive airway pressure may be used to support and
maintain adequate spontaneous ventilation and oxygenation.
Success Rate. Not all patients can be weaned from mechanical ventilation suc-
cessfully. One retrospective review of six studies reports that a combined 79% of
2,486 patients passed the initial SBT and the weaning success rate was 68.8%.
Thirteen percent of the patients who had passed the initial SBT required reintuba-
tion (Boles et al., 2007). The duration needed to wean a patient from mechanical
ventilation may also vary greatly. One study shows 15% of mechanically ventilated
patients required more than 7 days to be weaned successfully (Nett et al., 1984).
Since medical patients
often have coexisting prob- The success rate of weaning attempts is partly dependent on the patient popula-
lems, they usually take more tion. It is generally more difficult to predict the weaning outcome of patients with
time to complete the weaning
process than surgical patients. medical conditions. Since these patients often have coexisting or chronic medical
problems, they usually take more time to complete the weaning process than surgi-
cal patients (Yang et al., 1991).

weaning in progress: An
intermediate category (between Weaning in Progress
weaning success and weaning
failure) for patients who are
extubated but continue to receive Weaning in progress is an intermediate category (between weaning success and
ventilatory support by noninvasive
ventilation (NIV). weaning failure) for patients who are extubated but continue to receive ventilatory
support by noninvasive ventilation (NIV) (Boles et al., 2007). NIV is defined as me-
chanical ventilation without an artificial airway. With different NIV interfaces (e.g.,
Weaning failure is facial mask, nasal mask) NIV may be used to support a patient’s ventilatory require-
defined as either the failure
of spontaneous breathing ment following extubation. Use of NIV allows early weaning attempts and minimizes
trial (SBT) or the need for complications associated with prolonged mechanical ventilation and artificial airway.
reintubation within 48 hours
following extubation.
Weaning Failure

Weaning failure is more difficult to define than weaning success. This is because
weaning failure: Failure of
spontaneous breathing trial whenever a patient is placed back on the ventilator, the weaning attempt has failed
(SBT) or the need for reintuba- in one form or another. In most studies, weaning failure is defined as either the
tion within 48 hours following
extubation. failure of spontaneous breathing trial (SBT) or the need for reintubation within
48 hours following extubation. Patients who fail the SBT often exhibit the fol-
lowing clinical signs: tachypnea, tachycardia, hypertension, hypotension, hypox-

Patients who fail emia, acidosis, or arrhythmias. Physical signs of SBT failure may include agitation,
the SBT often exhibit the distress, diminished mental status, diaphoresis, and increased work of breathing
following clinical signs:
tachypnea, tachycardia, (Boles et al., 2007).
hypertension, hypotension, Failure to remain extubated and the need for reintubation impose another problem
hypoxemia, acidosis, or
arrhythmias. in the overall weaning process. Weaning becomes more challenging in patients with
an earlier failed attempt. Excessive secretions, hypercapnia, prolonged mechanical

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