My Presentation at a conference at Max Hospital, Saket, New Delhi

1. Ultrasound can replace Chest X-ray
in care of the Emergency Obese

2. Why do we need a better bedside test?
Significant flaws, particularly supine AP CXR
Prompt recognition/exclusion of thoracic trauma
Possible motion artifacts in a distressed patient
Rapid and accurate determination of the cause of
dyspnea
Post-procedural assessment
Risk to children and pregnant women

3. Thoracic USG??
Air would not allow useful ultrasound images to be
generated !!!
TRUE

4. BUT…
Intrathoracic air and water are intimately mixed.
From this mingling arise artifacts.
Lung ultrasound is mainly based on these artifact
analysis

5. Obese v/s Average population
Obese patients are suitable candidates since the
air/water impedance gradient enables satisfactory
analysis
Some ultrasound attenuation does occur across fat,
because of differences in velocities of ultrasound.
But that is true for CXR images as well!!

6. Ultrasound energy is attenuated by fat tissue at
higher frequencies.
Thoracic ultrasound typically utilizes the low
frequency range (1-5MHz)
Feature of Tissue Harmonic Imaging in USG
machines, eliminates echos arising from the main
ultrasound beam, increasing the quality of the image,
also reduces the scattering and distortion from the
body wall

7. Attenuation can be minimized by correct placement of
the transducer, and modifying patient position
Most studies showing ultrasound attenuation have been
performed on Abdominal USG while Thoracic USG
which is mainly of the upper anterior chest and the
axilla have lesser fat-pad than the abdomen in the obese

8. Speckle Reduction Imaging
Eliminates weak signals and enhances and brightens
the stronger signals

9. COMMON EMERGENCY
CONDITIONS
 Pleural effusion
 Static sign/“quad sign,” ie the effusions’ borders are regular
 Dynamic sign/the sinusoid sign, ie inspiratory decrease of
effusion thickness, confirmed in M-mode.

10.  93% sensitivity and specificity
(Bedside CXR has only 39% sensitivity)
Lichtenstein D, Goldstein I, Mourgeon E, et al. Comparative diagnostic performances of
auscultation, chest radiography and lung ultrasonography in acute respiratory distress
syndrome. Anesthesiology 2004; 100:9–15.
 “When the gold standard is withdrawal of pleural
fluid, specificity is 97%”
Lichtenstein D, Hulot JS, Rabiller A, et al. Feasibility and safety of ultrasound-aided
thoracentesis in mechanically ventilated patients. Intensive Care Med 1999; 25:955–958

11. What can Thoracic USG tell us?
 Volume (even as little as 15-30ml)
Collins JD, Burwell D, Furmanski S, et al. Minimal detectable pleural effusions. Radiology
1972; 105:51–53.
 Nature - Transudates anechoic, exudates echoic
Mobile particles (the plankton sign) or
septa - hemothorax or pyothorax.
Lichtenstein D, Goldstein I, Mourgeon E, et al. Comparative diagnostic performances of
auscultation, chest radiography and lung ultrasonography in acute respiratory distress
syndrome. Anesthesiology 2004; 100:9–15.

12. Optimum location for thoracentesis, preventing
subcutaneous placement in obese patients (success rate
97%, and complications nil to 1.3%)
Lichtenstein D, Hulot JS, Rabiller A, et al. Feasibility and safety of ultrasound-aided
thoracentesis in mechanically ventilated patients. Intensive Care Med 1999; 25:955–958.

13. “Considering the shorter time delay necessary to
have a final medical report from an ultrasound scan
compared with the standard radiographic
examination, without patient exposure to ionizing
radiations, chest ultrasonography could replace
standard chest radiography as the first routine
imaging modality used in patients with dyspnea
admitted to the ED”
Zanobetti M. Can chest ultrasonography replace standard chest radiography for evaluation of
acute dyspnea in the ED? Chest.
2011 May;139(5):1140-7. doi: 10.1378/chest.10-0435

14. “When compared directly to the supine chest x ray,
USG is shown to be more sensitive at detecting the
presence of traumatic haemothorax and is at least as
specific and accurate. It also has the added advantage
of being able to be performed in much less time”
PJ Boyle Ultrasound to detect haemothorax after chest injury
Emerg Med J. 2007 August; 24(8): 581–582.

15.  Pneumothorax
Can ultrasound detect gas (the main hindrance to
ultrasound) within a gas-containing organ?
Yes, with a better accuracy than radiography!

16.  Abolition of lung sliding Pnuemothorax can be discounted in a matter of
seconds
Sensitivity and negative predictive value 100%
Lichtenstein D, Menu Y. A bedside ultrasound sign ruling out pneumothorax in the
critically ill: lung sliding. Chest 1995; 108:1345–1348.
BUT, Specificity is 91%.....LOW?
Addition of the other two signs easily bypasses this
“issue”.

17.  A-line sign: no B line is visible – 100% sensitive
for the diagnosis, with a 60% specificity
Lichtenstein D, Meziere G, Biderman P, Gepner A. The comet-tail artifact, an
ultrasound sign ruling out pneumothorax. Intensive Care Med 1999; 25:383–388.
 Lung point: probe moves laterally until it finds a
location showing sudden inspiratory visualization
of lung sliding or B lines
An all-or-nothing law, Specificity 100%
Lichtenstein D, Meziere G, Biderman P, et al. The lung point: an ultrasound sign
specific
to pneumothorax. Intensive Care Med 2000; 26:1434–1440.

18. “Many are radio-occult on CXR, even if under
tension. Excessive search leads to overirradiation
and extra costs, and loss of valuable time, whereas an
overlooked pneumothorax is a clinical risk”
Hill SL, Edmisten T, Holtzman G, et al. The occult pneumothorax: an increasing
diagnostic entity in trauma. Annals Surg 1999; 65:254–258.

19. “The sensitivities of ultrasound and plain chest
x-ray for diagnosing traumatic pneumothorax
were 57% and 40%, respectively”
Ku BS et al. Clinician-performed bedside ultrasound for the diagnosis of traumatic
pneumothorax. West J Emerg Med 2013 March

20. Pulmonary Embolism
 Lung USG
Sensitivity 94%, Specificity 87%
Positive predictive value 92%, Negative
predictive value 91%
Accuracy 91%
Also can be used to look for DVT in lower limbs
Sevda Sener Comeret The role of thoracic ultrasonography in the diagnosis of
pulmonary embolism Ann Thorac Med. 2013 Apr-Jun; 8(2): 99–104.

21.  CXR
Sensitivity 70%, Specificity 59%
Greenspan RH, Ravin CE, Polansky SM, McLoud TC. Accuracy of the chest
radiograph in diagnosis of pulmonary embolism. Invest Radiol 1982; 17 (6): 539- 43

22.  Pneumonia
 Lung ultrasound: sonographic air bronchograms,
subpleural lung consolidation
Sensitivity 98%, Specificity 95%
 CXR
Sensitivity 67%, Specificity 85%
Francesca Cortellaro et al. Lung Ultrasound is an Accurate Diagnostic Tool for the
Diagnosis of Pneumonia in the ED Emerg Med J. 2012;29(1):19-23.

23.  Pulmonary Edema
 Sonographic anterior bilateral B lines –
96% specificity and 95% sensitivity
M. Ghanem et al Diagnostic accuracy of trans-thoracic chest ultrasonography in patients
with acute respiratory failure. Annual Congress Barcelona 2013

24.  USG comet-tail sign
100% sensitivity, 95% specificity
100% negative predictive value, 96% positive
predictive value
Gregor Prosen et al. Combination of lung ultrasound (a comet-tail sign) and N-terminal probrain natriuretic peptide in differentiating acute heart failure from chronic obstructive pulmonary
disease and asthma as cause of acute dyspnea in prehospital emergency setting. Critical Care
2011, 15:R114 doi:10.1186/cc10140

25. CXR
Among all signs ONLY cardiomegaly has a
sensitivity >50%
Specificity, for Cardiomegaly (71%),
Cephalisation (93%)
Kerley B lines
(96%)
Nicole Mueller-Lenke, et al Use of chest radiography in the emergency diagnosis of acute
congestive heart failure. Heart. 2006 May; 92(5): 695–696.

26. “CXR is only moderately accurate in the diagnosis of
CHF in patients presenting with acute dyspnoea to
the emergency department. Radiographic findings of
CHF are specific but only moderately sensitive”
Nicole Mueller-Lenke, et al Use of chest radiography in the emergency diagnosis of acute
congestive heart failure. Heart. 2006 May; 92(5): 695–696.

27.  Other Uses
Assessing tracheal trauma
Point of care USG:
USG Guided intubation
Post intubation confirmation

28. Percutaneous Tracheostomy - In obese patients
 Laryngeal and tracheal cartilages can be
identified
 Depth of the trachea from the skin
 Thickness of pretracheal fascia or tracheal
deviation
 Avoiding injury to an aberrant vessel

29. BLUE Protocol
Algorithmic approach (Bedside Lung Ultrasound in
Emergency)
Diagnostic accuracy 90.5%, in 3 minutes
Evaluated: Cardiogenic pulm edema
Pneumonia
Pulmonary embolism
Pnuemothorax
D Lichtenstein Lung USG in acute resp failure an introduction to BLUE protocol.
Minerva Anestesiol. 2009 May;75(5):313-7

30. Learning Curve!
Yes, But that's common to both modalities
“Physicians with minimal exposure to lung
ultrasound may be able to recognize pulmonary
edema on lung ultrasound more accurately than
with chest radiograph”
Martindale JL Diagnosing pulmonary edema: lung ultrasound versus chest
radiography.
Eur J Emerg Med. 2013 Oct;20(5):356-60

31. Conclusion
Provided minor limitations and rigorous training
are accepted, in addition to the well-known
advantages of ultrasound, one can add the major
advantage of simplicity
It Symbolizes for some the stethoscope of tomorrow
Greek: stethos (the chest wall) and scopein (to
observe)

32. THANK YOU