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462
PE
Volume removed
−
()
T. Ahmad and J.-T. Chen
Manometry
Manometry can be used as a safeguard to monitor
pleural pressures to help prevent complications
of thoracentesis such as pulmonary edema, chest
discomfort, and breathlessness, especially in
those with non-expanding lungs due to trapped
lung. Pressures lower than −20cm H2O are cited
as excessively negative based on early research
models, where pressures greater than this had the
lowest incidence of complications [11]. These
complications are more likely to occur in those
with lung entrapment or trapped lung. Manometry
can be performed in various ways by connecting
the pleural catheter to either a digital manometer,
a hemodynamic transducer with an ICU monitor,
or a column manometer. Your choice of monitor
is attached to the pleural catheter and measurements can be taken in intervals after removing
aliquots of uid. Measurements are taken during
expiration. Pleural elastance can be calculated by
taking an initial pleural pressure measurement,
subtracting the nal pleural pressure measurement after completing thoracentesis, and dividing
it by the amount of uid removed (calculated in
H2O/L).
Opening pressure Closing pressure
L
=
While manometry can assist in mitigating
complications, it is not commonly performed,
and often symptoms during thoracentesis are
used to guide the clinician’s removal of uid. A
2019 randomized single blinded study on the utilization of manometry during large volume thoracentesis to prevent related complications
demonstrated that its utilization did not lead to a
statistically signicant reduction in procedure
related chest discomfort [12]. There were some
limitations to the study, such as most patients had
1L of uid or less removed (60%), with fewer
patients having more than 1.2L of uid removed,
which questions whether the study ndings are
generalizable to those patients who have large
volume thoracentesis performed [13].
Procedural Complications
Complications during performance of thoracentesis and tube thoracostomy can occur. These
complications include pneumothorax, bleeding,
re-expansion pulmonary edema [5], as well as
pain, and procedure failure. Pneumothorax has a
higher incidence of occurrence when thoracentesis is performed without ultrasound guidance
[14]. Bleeding can manifest as puncture site
bleeding, intercostal blood vessel injuries resulting in hemothorax, and chest wall hematoma.
Use of ultrasound to identify vasculature prior to
procedure can assist in reducing the risk of bleeding. Finally, re-expansion pulmonary edema,
while uncommon, can occur after thoracentesis,
and manifests as hypoxemia and new inltrates
on chest X-ray within 24h of thoracentesis, usually within in the re-expanded lung.
The Need forChest X-Ray After
Thoracentesis
Some proceduralists may obtain a chest X-ray
post procedurally after a thoracentesis to conrm
the absence of a pneumothorax. Early literature
has suggested that thoracentesis had a considerable rate of pneumothorax ranging from 5.2% to
as high as 26% [14]. However, ultrasound guided
thoracentesis has shown to have signicantly
reduced this risk. A 1997 retrospective review of
ultrasound guided thoracentesis by Gervais etal.
found that out of 434 patients who underwent
thoracentesis (342 spontaneously breathing, 92
intubated), only 10 patients developed a pneumothorax (6in intubated patients, and 4in spontaneously breathing patients) [15]. In another
retrospective study of ultrasound guided thoracentesis by Cavanna etal. in 2014, among 445
patients with malignant pleural effusions who
underwent thoracentesis with and without ultrasound, pneumothorax occurred in less than 1% of
those guided with ultrasound (3/310), and in
8.89% of those without ultrasound guidance
39 Thoracentesis andThoracostomy Procedural Guidance
463
(12/135) [14]. Tube thoracostomy was required
in three patients only, and only in those who had
thoracentesis performed without ultrasound.
Pneumothorax can occur due to several reasons,
such as introduction of air during procedure into
the pleural cavity, direct lung puncture, and failure for the lung to expand after removal of uid,
known as pneumothorax ex vacuo. Pneumothorax
ex vacuo does not require treatment with a chest
tube. A review of the available literature suggests
obtaining a repeat chest radiograph after thoracentesis if the patient had multiple attempts, if
there was aspiration of air, if they are on a
mechanical ventilator, if large volume thoracentesis was performed, or if they have advanced
lung disease [16]. The decision to obtain a chest
radiograph should be guided by patient symptoms and clinical suspicion. Ultrasound should
also be utilized to check for post-procedural
pneumothorax after a thoracentesis and be used
to assess for residual pleural effusion in lieu of
chest X-ray and has the benet of preventing
additional radiation exposure. Outside of the
above, obtaining routine chest radiography to
rule out pneumothorax after a thoracentesis is not
required [3]. Obtaining a chest radiograph after
tube thoracostomy is a usual practice and should
be performed post procedurally.
Subpleural Mass Biopsy
Ultrasound has been shown to be safe and effective in ultrasound-guided needle biopsies of subpleural masses. A retrospective study by
Mychajlowycz etal. found that ultrasound and CT
guidance for subpleural biopsies have similar
safety and diagnostic adequacy but with the benet of shorter procedure times and wait times when
done under ultrasound guidance [17]. The lesions
biopsied in this study were noted to be larger than
those biopsied by CT, with an average axial diameter of 4.8cm (±2.6) compared to lesions biopsied
via CT with an average axial diameter of 3.2cm
(±1.9), and additionally demonstrated equivalent
sampling adequacy and similar rate of pneumothoracies. Biopsies were performed with a semi-automatic 18-gauge needle with a Menghini type tip.
Furthermore, a prospective analysis on the diagnostic accuracy of ultrasound guided subpleural
mass biopsies by Sperandeo etal. found that ultrasound guided biopsies were 93% accurate with
0.79% rate of pneumothorax, demonstrating that
ultrasound guidance is both safe and effective
compared to CT guidance [18]. Diagnostic accuracy in this study however depended on the size of
the subpleural mass, with masses greater than
5.0cm and smaller than 2.0 cm having a higher
rate of non-statistically signicant non-diagnostic
biopsies compared to masses with sizes between
2.0cm and 5.0cm.
Conclusion
Thoracentesis and tube thoracostomy are critical
procedures for clinicians to perform precisely and
safely. The use of ultrasound has allowed for
intensivists to mitigate the risk of pneumothorax
and organ injury. In addition, ultrasound can be
used to conrm lung re-expansion after chest tube
placement for pneumothorax and to re- assess the
pleural space after uid drainage, helping to
reduce the need for chest X-ray. Ultrasound is
used to interrogate the site of procedure for ndings that ensure safety, such as, largest area with
absence of lung sliding, and largest uid pocket
for pneumothoracies and pleural effusions,
respectively. Symptom monitoring during therapeutic thoracentesis is largely used over manometry. Finally, ultrasound is safe and effective in
obtaining subpleural biopsies, with the added
benet of shorter wait times for the procedure.
Summary Points
• Use ultrasound to interrogate the site of the
procedure to identify vital structures, vasculature, and to plan the approach for thoracentesis and tube thoracostomy for pneumothorax
and pleural uid drainage.
464
T. Ahmad and J.-T. Chen
• Use direct ultrasound guidance whenever possible to increase safety, success, and to help
prevent complications.
• Manometry is not used commonly during
pleural uid drainage but can be an additional
safeguard. Pleural drainage should be stopped
upon the patient experiencing chest
discomfort.
• Routine chest X-ray is not needed after thoracentesis, unless air has been aspirated, multiple attempts were made, the patient is on a
mechanical ventilator, or if the patient
becomes symptomatic. Use ultrasound to
check for pneumothorax after thoracentesis
instead.
• Ultrasound is safe for subpleural mass biopsies, has similar yield to CT guided biopsies,
and has benets of shorter procedure and wait
times.
Questions
1. A 40-year-old man with type 1 diabetes melli-
tus (DM1), hypertension, and interstitial lung
disease (ILD) is admitted to the ICU for respiratory failure due to inuenza A and Diabetic
Ketoacidosis (DKA). Bedsides, ultrasound
performed demonstrates a moderate left sided
pleural effusion adjacent to consolidated lung
with air bronchograms. Which of the following
after performing bedside thoracentesis would
necessitate performing a portable chest X-ray?
A. Mechanical ventilation
B. History of interstitial lung disease
C. Multiple attempts during thoracentesis
D. Aspiration of free air during the
procedure
E. All of the above
Answer: E
2. Which of the following statements is true
regarding the use of ultrasound in performing
thoracentesis and tube thoracostomy?
A. Tube thoracostomy under ultrasound
guidance does not lead to fewer subdiaphragmatic chest tubes.
B. The incidence of pneumothorax is the
same after thoracentesis and tube thoracostomy with and without ultrasound
guidance.
C. Landmark based tube thoracostomy place-
ment leads to the same incidence of iatrogenic injury when compared to ultrasound
guided placement.
D. Ultrasound-guided thoracentesis has a lower
incidence of post-procedural pneumothorax.
Answer: D
References
1. Kalanjeri S, Pastores SM.Thoracentesis. In: Oropello
JM, Pastores SM, Kvetan V, editors. Critical care.
McGraw-Hill Education.
2. Kollef MH, Isakow W, Burks AC, Despotovic V,
Burks AC, Chen AC.Thoracentesis. The Washington
manual of critical care. 3rd ed. Wolters Kluwer; 2018.
p.695–700. Chapter 81
3. Havelock T, Teoh R, Fau-Laws D, Laws D, FauGleeson F, Gleeson F.Pleural procedures and thoracic
ultrasound: British Thoracic Society Pleural Disease
Guideline 2010. (1468–3296 (Electronic)).
4. Shechtman L, Shrem M, Kleinbaum Y, Bornstein G,
Gilad L, Grossman C.Incidence and risk factors of
pneumothorax following pre-procedural ultrasoundguided thoracentesis. J Thorac Dis. 2020;12(3):942–8.
https://doi.org/10.21037/jtd.2019.12.39.
5. Cantey EP, Walter JM, Corbridge T, Barsuk
JH. Complications of thoracentesis: incidence, risk
factors, and strategies for prevention. Curr Opin Pulm
Med. 2016;22(4):378–85. https://doi.org/10.1097/
MCP.0000000000000285.
6. Taylor LA, Stenberg R, Tozer J, etal. Novel approach
to ultrasound-guided thoracostomy. J Ultrasound
Med. 2022;41(3):743–7. https://doi.org/10.1002/
jum.15759.
7. Gray EJ, Cranford JA, Betcher JA, et al. Sonogram
of safety: ultrasound outperforms the fth intercostal
space landmark for tube thoracostomy site selection.
J Clin Ultrasound. 2020;48(6):303–6. https://doi.
org/10.1002/jcu.22851.
8. Zisis C, Tsirgogianni K, Lazaridis G, etal. Chest drainage systems in use. Ann Transl Med. 2015;3(3):43.
https://doi.org/10.3978/j.issn.2305- 5839.2015.02.09.
9. Rahman NM, Maskell NA, West A, etal. Intrapleural
use of tissue plasminogen activator and DNase in
pleural infection. N Engl J Med. 2011;365(6):518–26.
https://doi.org/10.1056/NEJMoa1012740.
10. Watson GAHB.E12: chest tube placement, care, and
removal. In: Texbook of critical care. 7th ed. Elsevier;
2016.
11. Light RW, Jenkinson SG, Minh VD, George
RB.Observations on pleural uid pressures as uid
is withdrawn during thoracentesis. Am Rev Respir
Dis. 1980;121(5):799–804. https://doi.org/10.1164/
arrd.1980.121.5.799.
39 Thoracentesis andThoracostomy Procedural Guidance
465
12. Lentz RJ, Lerner AD, Pannu JK, et al. Routine
monitoring with pleural manometry during therapeutic large-volume thoracentesis to prevent
pleural- pressure-related complications: a multicentre, single-blind randomised controlled trial.
Lancet Respir Med. 2019;7(5):447–55. https://doi.
org/10.1016/s2213- 2600(18)30421- 1.
13. Krenke R, Grabczak EM. Pleural manometry and
thoracentesis—is the issue resolved? Lancet Respir
Med. 2019;7(5):374–6. https://doi.org/10.1016/
s2213- 2600(19)30033- 5.
14. Cavanna L, Mordenti P, Bertè R, et al. Ultrasound
guidance reduces pneumothorax rate and improves
safety of thoracentesis in malignant pleural effusion:
report on 445 consecutive patients with advanced cancer. World J Surg Oncol. 2014;12(1):139. https://doi.
org/10.1186/1477- 7819- 12- 139.
15. Gervais DA, Petersein A, Lee MJ, Hahn PF, Saini
S, Mueller PR. US-guided thoracentesis: requirement for postprocedure chest radiography in
patients who receive mechanical ventilation ver-
sus patients who breathe spontaneously. Radiology.
1997;204(2):503–6. https://doi.org/10.1148/
radiology.204.2.9240544.
16. Mirrakhimov AE, Barbaryan A, Ayach T, Canepa
Escaro F, Talari G, Gray A. Is chest radiography
routinely needed after thoracentesis? Cleve Clin J
Med. 2019;86(6):371–3. https://doi.org/10.3949/
ccjm.86a.17058.
17. Mychajlowycz M, Alabousi A, Mironov
O. Ultrasound- versus CT-guided subpleural lung
and pleural biopsy: an analysis of wait times, procedure time, safety, and diagnostic adequacy. Can
Assoc Radiol J. 2021;72(4):883–9. https://doi.
org/10.1177/0846537120939073.
18. Sperandeo M, Maiello E, Graziano P, et al.
Effectiveness and safety of transthoracic ultrasound in guiding percutaneous needle biopsy in the
lung and comparison vs. CT scan in assessing morphology of subpleural consolidations. Diagnostics
(Basel). 2021;11(9):1641. https://doi.org/10.3390/
diagnostics11091641.
Ultrasound During Intubation
YouyouDuanmu andErinJ.Liang
40
Learning Objectives
1. Recognize sonographic ndings of tracheal
and esophageal anatomy
2. Identify sonographic ndings of tracheal intubation and esophageal intubation
Anatomy andTechnique
Ultrasound has been proposed as an adjunct for
visualizing and conrming endotracheal intubation in the acute care setting in conjunction with
video laryngoscopy, capnography, lung auscultation, and chest X-ray. The high-frequency linear
probe is most commonly used to visualize airway
anatomy under ultrasonography, the curvilinear
probe can be used in patients with greater neck
soft tissue depth. Place the probe above the suprasternal notch in the transverse plane with the
indicator to the patient’s right. Identify the proximal wall of the trachea and the esophagus. When
viewed under ultrasonography the trachea is a
midline, curved hyperechoic structure with posterior shadowing. The esophageal is located pos-
Y. Duanmu (*)
Department of Emergency Medicine, Stanford
University School of Medicine, Palo Alto, CA, USA
e-mail: yduanmu@stanford.edu
E. J. Liang
Department of Emergency Medicine, Kaiser
Permanente San Diego, San Diego, CA, USA
terior and lateral, most often to the patient’s left,
of the trachea and appears as a smaller oblong
structure. Move the probe laterally if unable to
identify the esophagus as it may be underlying
the trachea shadow. The carotid arteries will also
appear lateral to the trachea. Do not mistake the
carotid artery for the esophagus, the carotid
artery will be a more lateral, round-walled,
hypoechoic and pulsating structure [1, 2]
(Fig.40.1).
For real-time assessment of endotracheal tube
(ETT) placement, the trachea and esophagus
should be identied prior to intubation and
dynamic monitoring of the trachea and esophagus should continue as the endotracheal tube is
being advanced during intubation. Successful tracheal intubation will result in increased mucosal
air artifact and shadowing of the trachea as the
tube enters. The sonographer should simultaneously assess for signs of esophageal intubation. If
an esophageal intubation occurs, a second round
structure with a hyperechoic anterior rim and
hypoechoic shadowing appears just lateral and
behind the trachea, almost appearing as if there is
a second trachea (“double-tract” sign) [3].
Static ultrasonography can also be used to
conrm endotracheal tube placement after intubation has already occurred. Ultrasound following successful tracheal intubation will show a
single, midline air-mucosal interface with shadowing representing the trachea with ETT in
place. Conversely if esophageal intubation has
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2025
M. J. Lanspa, A. T. Levinson (eds.), Echocardiography and Ultrasonography in the ICU,
Respiratory Medicine, https://doi.org/10.1007/978-3-031-80038-2_40
467
468
a b
Y. Duanmu and E. J. Liang
Fig. 40.1 (a) The linear ultrasound transducer is placed
1–2cm above the suprasternal notch in the transverse orientation. (b) The trachea is a supercial, midline structure
with a hyperechoic anterior arch with posterior shadowing
occurred, two rounded air-lled artifacts or the
“double-tract” sign is seen. A gentle side-to-side
rotation of the ETT while visualizing the above
structures on ultrasound can help conrm its
location by the presence of motion artifact [4].
Lung ultrasound has been utilized in many
clinical settings for the detection of lung expansion with respiration, which is reected as movement at the junction of the visceral and parietal
pleura. This motion at the pleural line is lost in
the presence of pneumothorax, lung scarring,
pulmonary bleb, or in the absence of mechanical
ventilation in intubated patients. To assess for
expansion of each lung, the linear transducer is
placed in the sagittal orientation between the second and third rib in the midclavicular line. Each
rib is delineated by a thin anterior hyperechoic
arch with dark posterior shadowing and the
hyperechoic pleural line is seen between and
slightly posterior to the ribs. Lung sliding movement seen at the pleural line bilaterally indicates
tracheal intubation, while lack of lung sliding of
one lung suggests either ipsilateral pneumothorax or mainstem bronchial intubation of the contralateral side.
and anked by the thyroid gland (Th). The esophagus
(Esoph) is a muscular-walled ovoid structure slightly lateral and posterior to the trachea. The carotid arteries (c)
may be visible lateral to the trachea and esophagus
Evidence
The utility of ultrasonography to conrm ETT
placement was summarized in a 2020 metaanalysis of 30 studies involving over 2500
patients. The majority of studies took place in the
emergency department, four were performed in
the critical care setting. There were 28 prospective observational studies and two randomized
controlled trials. Ultrasound showed good accuracy for differentiating between tracheal and
esophageal intubation with a pooled specicity
of 98.2% and a pooled specicity of 95.7% [5].
There is emerging evidence to expand the use
of ultrasound for ETT conrmation and to predict the difculty of intubation as well as intubation depth. While color doppler has been proposed
as an adjunct for dynamic monitoring of ETT
placement, studies comparing color doppler with
B-mode ultrasound have not shown superior
accuracy for visualizing tracheal vs esophageal
intubation [6, 7]. Ultrasound has also been studied as a tool for predicting challenging ETT
placement. Measurements such as increased distance from skin surface to the hyoid bone or
40 Ultrasound During Intubation
469
epiglottis (as measured in the transverse plane),
and increased hyomental distance (as measured
in the sagittal plane with probe placed below the
mandible) have been associated with difcult
intubation [8, 9].
For assessing depth of intubation, one study
showed that ultrasound to assess for anterior lung
sliding had superior sensitivity (93 vs. 66%) and
specicity (96 vs. 59%) for differentiating tracheal from bronchial mainstem intubation relative
to lung auscultation [10]. In the pediatric population, lling the ETT balloon with saline and evaluating for its presence at the sternal notch has
been proposed to aid in the assessment of intubation depth, while measuring the subglottic trachea
diameter has been used to predict proper ETT size
[11, 12]. Further validation may be required for
these emerging airway ultrasound techniques.
Limitations
Monitoring for tracheal intubation requires identifying pertinent ultrasound anatomy prior to the
procedure. The visibility of normal trachea and
esophageal landmarks can vary between patients.
Esophageal intubation can be difcult to identify
if the esophagus is directly underlying the trachea. Therefore, it is helpful to identify the collapsed esophagus prior to intubation, and to
attempt a more lateral view if it is not visible
from the midline transverse probe orientation.
Summary Point
• Ultrasound shows good accuracy for differen-
tiating between tracheal and esophageal
intubation.
Question
1. What qualities distinguish the trachea from
the esophagus on ultrasound?
A. The esophagus has a posterior air shadow
behind it.
B. The trachea has a hyperechoic anterior
border.
C. The trachea is generally lateral and poste-
rior relative to the esophagus.
D. The esophagus may contain lines parallel
to the anterior border due to
reverberation.
Answer: B
Explanation: The trachea can be differenti-
ated from the esophagus on ultrasound by its
hyperechoic anterior border with posterior
shadowing. Parallel hyperechoic lines may
also be seen posterior to the trachea border
reecting reverberation artifact from the air
mucosal interface of the trachea.
Conicts of Interest The authors have no real or potential conicts of interest related to the manuscript.
References
1. Chou EH, Dickman E, Tsou PY, etal. Ultrasonography
for conrmation of endotracheal tube placement: a
systematic review and meta-analysis. Resuscitation.
2015;90:97–103.
2. Das SK, Choupoo NS, Haldar R, etal. Transtracheal
ultrasound for verication of endotracheal tube placement: a systematic review and meta-analysis. Can J
Anesth. 2015;62(4):413–23.
3. You-Ten KE, Siddiqui N, Teoh WH, et al. Point-ofcare ultrasound (POCUS) of the upper airway. Can J
Anesth. 2018;65(4):473–84.
4. Gottlieb M, Nakitende D, Sundaram T, et al.
Comparison of static versus dynamic ultrasound
for the detection of endotracheal intubation. West J
Emerg Med. 2018;19(2):412–6.
5. Sahu AK, Bhoi S, Aggarwal P, et al. Endotracheal
tube placement conrmation by ultrasonography: a
systematic review and meta-analysis of more than
2500 patients. J Emerg Med. 2020;59(2):254–64.
6. Gildea TH, Anderson KL, Niknam KR, et al. The
utility of color doppler to conrm endotracheal
tube placement: a pilot study. West J Emerg Med.
2020;21(4):870–5.
7. Gottlieb M, Holladay D, Serici A, etal. Comparison
of color ow with standard ultrasound for the detection of endotracheal intubation. Am J Emerg Med.
2018;36(7):1166–9.
8. Alessandri F, Antenucci G, Piervincenzi E, et al.
Ultrasound as a new tool in the assessment of airway
difculties: an observational study. Eur J Anaesthesiol.
2019;36(7):509–15.
470
Y. Duanmu and E. J. Liang
9. Abraham S, Himarani J, Mary Nancy S, et al.
Ultrasound as an assessment method in predicting
difcult intubation: a prospective clinical study. J
Maxillofac Oral Surg. 2018;17(4):563–9.
10. Ramsingh D, Frank E, Haughton R, etal. Auscultation
versus point-of-care ultrasound to determine endotracheal versus bronchial intubation. Anesthesiology.
2016;124(5):1012–20.
11. Tessaro MO, Arroyo AC, Haines LE, etal. Inating
the endotracheal tube cuff with saline to conrm
correct depth using bedside ultrasonography. Can J
Emerg Med. 2015;17(1):94–8.
12. Shibasaki M, Nakajima Y, Ishii S, Shimizu F, Shime
N, Sessler DI. Prediction of pediatric endotracheal tube size by ultrasonography. Anesthesiology.
2010;113(4):819–24.
Transcutaneous Laryngeal Ultrasonography: Vocal Fold Ultrasound
AkivaLeibowitz andAchikamOren-Grinberg
41
Introduction
Multimodal ultrasound has been recognized as a
potentially useful tool for noninvasively evaluating the airways and vocal folds, with the
increasing availability of this tool for use by
bedside clinicians since the 1980s [1–3].
B-mode ultrasound can be used to identify glottic structures and their dynamic movements,
while spectral doppler can be utilized to evaluate motion and vibration. Some vocal movement
disorders such as bilateral vocal cord paralysis,
paradoxical vocal fold motion movement abnormalities, arytenoid dislocation, and laryngeal
edema may be the underlying pathologies causing respiratory distress and stridor. Laryngeal
nerve injury has been reported during thyroid,
anterior cervical spine, esophageal, and mediastinal surgical procedures in the surgical patient
population. The reported incidence is 2.3%
among patients following cardiac and great vessel surgery [4], 3.9% following initial thyroid
surgery [5], and 45.3% following radical esoph-
Supplementary Information The online version contains supplementary material available at https://doi.
org/10.1007/978- 3- 031- 80038- 2_41.
agectomy [6]. Paradoxical vocal motion abnormalities occur when vocal cords close (adduct)
rather than abduct when they should be opening
(mostly on inspiration) and may present with
inspiratory stridor and respiratory distress [7].
Hence, early identication of these abnormalities may have a role in the management of
patients presenting with respiratory distress or
in those developing post-extubation respiratory
failure in the ICU.The mainstay for diagnosis
of vocal cord motion abnormalities remains
clinical exam and indirect beroptic laryngoscopy (IFL) [8], which may be replaced in certain instances with less invasive Transcutaneous
Laryngeal Ultrasonography (TLUS). Ultrasound
has been used for the identication of important
laryngeal landmarks (Thyroid cartilage, cricothyroid membrane, laryngeal rings, vocal folds,
arytenoid cartilage, and vascular structures) as
well as delineating functionality (vocal fold
movement, vocal cord palsies). The unique
characteristics of the larynx, particularly the
presence of air in the laryngotracheal space,
encased by cartilaginous structures—present
unique challenges when assessing the airway
with ultrasound.
A. Leibowitz (*) · A. Oren-Grinberg
Department of Anesthesia, Critical Care and Pain
Medicine, Harvard Medical School, Beth Israel
Deaconess Medical Center, Boston, MA, USA
e-mail: aleibow1@bidmc.harvard.edu
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2025
M. J. Lanspa, A. T. Levinson (eds.), Echocardiography and Ultrasonography in the ICU,
Respiratory Medicine, https://doi.org/10.1007/978-3-031-80038-2_41
471
472
A. Leibowitz and A. Oren-Grinberg
Ultrasound Anatomy oftheVocal
Cords
A standard linear high-frequency probe
(6–13MHz) may be used for the visualization of
laryngeal structures. Low-frequency curvilinear
probes (2–5 MHz) may be used as well, albeit
with some loss of resolution. The vocal cords are
composed of mucous membrane infoldings
attached anteriorly at the angle on the interior
surface of the thyroid cartilage and project posteriorly to the arytenoid cartilages on either side
[9]. The true vocal cords overlie hypoechoic
muscle, whereas the false cords contain echoic
fat. The tissue air interface appears on ultrasound
as a bright white line, for which anything behind
it will be considered an artifact. The vocal folds
are visualized by placing the transducer transversely over the thyroid cartilage, slightly tilting
Fig. 41.1 (a)
Ultrasound anatomy of
anterior neck, at level of
thyroid cartilage. Image
obtained with a
curvilinear, low
frequency probe. (b)
Ultrasound anatomy of
anterior neck, at level of
thyroid cartilage. Image
obtained with a linear,
high frequency probe.
Red dotted line:
Thyroid cartilage, Blue
lines: Vocal cords, with
apex at anterior
commissure, Tr:
Trachea, AC: Arytenoid
cartilage, FVF: False
vocal folds, SM: Strap
muscle, STA: Superior
thyroid artery
a
b
the probe cephalad (Fig.41.1). A study with 24
healthy volunteers showed that the thyroid cartilage provides the best acoustic window [2], with
the operator able to identify true and false vocal
cords in all participants. Calcied thyroid cartilage and male gender have been associated with
impaired ability to adequately visualize the vocal
cords [10]. However, in individuals with calcied
thyroid cartilages, the vocal cords and the arytenoid cartilages can still be seen by combining the
scanning from just cranially to the superior thyroid notch angled caudally and scanning from the
cricothyroid membrane in the midline and on
each side with the transducer angled 30° cranially [1]. A lateral approach, with the transducer
placed at a 30° angle—has been shown to
improve overall vocal cord visualization rate
compared to the midline approach (93.3 vs.
82.2%, p = <0.001), especially for males (75.0