Date post: | 16-Apr-2017 |
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Health & Medicine |
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Diaphragm Ultrasound as a
Novel Guide of Weaning from
Invasive Ventilation
Gamal Agmy , MD , FCCP Professor of Chest Diseases and respiratory ICU,
Assiut University, Assiut , Egypt
• Difficulties in weaning from
mechanical ventilation are
encountered in approximately 20%
of patients, and more than 40% of
the time passed in the intensive
care unit is spent to try to wean off
from mechanical ventilation
• Several indexes have been employed to assess the patient's ability to recover spontaneous breathing.
• Variables such as minute ventilation (Ve), maximum
inspiratory pressure (PImax), breathing frequency, rapid shallow breathing index (RSBI, i.e., respiratory
frequency/tidal volume), tracheal airway occlusion
pressure 0.1 s (P 0.1), and a combined index named CROP (compliance, rate, O2, pressure index) have
been used in common clinical practice
• Among the numerous parameters used
in clinical practice, the rapid shallow
breathing index is one of the most
accurate.
Objective
• The diaphragm thickening (DT)
measured by ultrasound was
evaluated as a weaning predictor
compared with the rapid shallow
breathing index.
• A prospective study included 78
patients with COPD exacerbation.
• All patients were ventilated in pressure
support through endotracheal tube.
• Both diaphragms were assessed by
chest ultrasound and those with
unilateral dusfunction were excluded
from study
.
• During spontaneous breathing trial
(SBT), the right diaphragm was
visualized in the zone of apposition
using a 7.5 MHz linear ultrasound
probe.
• The equipment used were ultrasound
apparatus (ALOKA – Prosound – SSD –
3500SV)
Diaphragm Thickness (DT)
• High frequency transducer 7.5
MHz
• Anterior axillary line
• Sagittal image at the intercostal
space between the 7th/8th , 8th /9th
ribs
• Visualization of both the pleural
and peritoneal membranes at all
times while imaging the diaphragm
for thickness measurements.
• Zone of apposition
• DT was calculated as percentage
from the following formula:
T end-inspiration − T end-expiration
T end-expiration
• It was recorded at total lung
capacity (TLC) and residual volume
(RV).
• The rapid shallow breathing index
(RSBI) was calculated.
• Weaning failure was defined as the
inability to maintain spontaneous
breathing for at least 48 h, without
any form of ventilatory support.
• A significant difference between
diaphragm thickness at TLC and RV
was observed both in patients who
succeeded SBT and patients who
failed.
• DT was significantly different between
patients who failed and patients who
succeeded SBT.
• A cutoff value of a DT >40% was
associated with a successful SBT with a
sensitivity of 88%, a specificity of 92%, a
positive predictive value (PPV) of 95%,
and a negative predictive value (NPV) of
82%.
• On the other hand , RSBI <105 had
a sensitivity of 95%, a specificity of
90%, a PPV of 96%, and a NPV of
92% for determining SBT success.
Accuracy of US and RSBI in
prediction of successful
weaning:
• DT assessed by ultrasound is an
excellent predictor of weaning
outcome in COPD patients
undergoing mechanical ventilation.