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

http://www.youtube.com/watch?v=bFcYP8xDRmM

• 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.