Page 566 - Clinical Application of Mechanical Ventilation

532 Chapter 16

Early signs of weaning failure include tachypnea, use of accessory muscles, and
Patients may hyperven- paradoxical abdominal movements (Cohen et al., 1982). It is important to evalu-
tilate due to hypoxia, pain,
anxiety, or inappropriate ven- ate and apply clinical data in conjuction with the patient’s clinical presentations.
tilator settings. It is a grave Patients may hyperventilate due to hypoxia, pain, anxiety, or inappropriate ventila-
mistake to reduce ventilatory
support simply because the tor settings. It is a grave mistake to reduce ventilatory support simply because the
PaCO 2 shows hyperventilation. PaCO shows hyperventilation.
2
Other indications that the patient cannot maintain the work of breathing may
include dyspnea, chest pain, chest-abdomen asynchrony, diaphoresis, and delirium
Early signs of weaning (Ely et al., 2004; Jabour et al., 1991). Some specific indicators of weaning failure
failure include: tachypnea, are listed in Table 16-7.
use of accessory muscles and
paradoxical abdominal move- If the patient does not tolerate the weaning procedure, the patient should be re-
ments, dyspnea, chest pain, turned to full ventilatory support and be allowed to rest. The patient should then be
chest-abdomen asynchrony,
and diaphoresis. reassessed in order to determine the cause of weaning failure. Appropriate therapies
may then be applied before attempting the weaning process again.

TABLE 16-7 Indicators of Weaning Failure

Indicators Examples

Blood Gases Increasing PaCO (.50 mm Hg)
2
Decreasing pH (,7.30)
Decreasing PaO (,60 mm Hg)
2
Decreasing SpO (,90%)
2
Decreasing PaO /F O (,150 mm Hg)
2
2
I
Vital Signs Changing blood pressures (20 mm Hg systolic
or 10 mm Hg diastolic)
Increasing heart rate (by 20/min, or .110/min)
Abnormal ECG (presence of arrhythmias)

Respiratory Decreasing V (,250 mL)
T
Parameters
Increasing f (.30/min)
Increasing f/V (.100 breaths/min/L)
T
Decreasing MIP (,220 cm H O)
2
Decreasing static compliance (,30 mL/cm H O)
2
Increasing V /V (.60%)
D
T
(Data from Burton et al., 1997; Girault et al., 1994; Jabour et al., 1991; Jubran & Tobin, 1997; MacIntyre, et al., 2001;
Tobin et al., 1990; Yang et al., 1991.)
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