chest usg vs cxr in emergency obese

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

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

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Page 1: Chest USG vs CXR in Emergency Obese

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

Page 2: Chest USG vs CXR in Emergency Obese

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

Page 3: Chest USG vs CXR in Emergency Obese

Thoracic USG??

Air would not allow useful ultrasound images to be generated !!!

TRUE

Page 4: Chest USG vs CXR in Emergency Obese

BUT…

I

Intrathoracic air and water are intimately mixed.

From this mingling arise artifacts.

Lung ultrasound is mainly based on these artifact

analysis

Page 5: Chest USG vs CXR in Emergency Obese

Obese v/s Average population O

Obese patients are suitable candidates since the

air/water impedance gradient enables satisfactory

analysis

S

Some ultrasound attenuation does occur across fat,

because of differences in velocities of ultrasound.

B

But that is true for CXR images as well!!

Page 6: Chest USG vs CXR in Emergency Obese

UUltrasound energy is attenuated by fat tissue at higher frequencies.

Thoracic ultrasound typically utilizes the low frequency range (1-5MHz)

FFeature 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

Page 7: Chest USG vs CXR in Emergency Obese

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

Page 8: Chest USG vs CXR in Emergency Obese

SSpeckle Reduction Imaging

EEliminates weak signals and enhances and brightens the stronger signals

Page 9: Chest USG vs CXR in Emergency Obese

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.

Page 10: Chest USG vs CXR in Emergency Obese

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

Page 11: Chest USG vs CXR in Emergency Obese

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.

Page 12: Chest USG vs CXR in Emergency Obese

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.

Page 13: Chest USG vs CXR in Emergency Obese

“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

Page 14: Chest USG vs CXR in Emergency Obese

“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.

Page 15: Chest USG vs CXR in Emergency Obese

Pneumothorax

Can ultrasound detect gas (the main hindrance to

ultrasound) within a gas-containing organ?

Yes, with a better accuracy than radiography!

Page 16: Chest USG vs CXR in Emergency Obese

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”.

Page 17: Chest USG vs CXR in Emergency Obese

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.

Page 18: Chest USG vs CXR in Emergency Obese

“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.

Page 19: Chest USG vs CXR in Emergency Obese

“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

Page 20: Chest USG vs CXR in Emergency Obese

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.

Page 21: Chest USG vs CXR in Emergency Obese

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

Page 22: Chest USG vs CXR in Emergency Obese

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. 

Page 23: Chest USG vs CXR in Emergency Obese

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

Page 24: Chest USG vs CXR in Emergency Obese

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 pro-

brain 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

Page 25: Chest USG vs CXR in Emergency Obese

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.

Page 26: Chest USG vs CXR in Emergency Obese

“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.

Page 27: Chest USG vs CXR in Emergency Obese

Other Uses

Assessing tracheal trauma

Point of care USG:

USG Guided intubation

Post intubation confirmation

Page 28: Chest USG vs CXR in Emergency Obese

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

Page 29: Chest USG vs CXR in Emergency Obese

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

Page 30: Chest USG vs CXR in Emergency Obese

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

Page 31: Chest USG vs CXR in Emergency Obese

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)

Page 32: Chest USG vs CXR in Emergency Obese

THANK YOU