Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / @xirurgi_2025 / @xirurgi_2025 - 442 - файл
.pdf
18 How to Teach Teamwork and Leadership Skills Eectively from Outside the Operating Room…
https://t.me/medicina_free
193
their thoughts regarding the intersection and
appropriate balance between being a leader
and working as part of a team.
Sixth Session: Assignment—Discuss how and
why teamwork is important and how to lead a
team to solve a problem. Then assign discus-
sion of a surgical complication, and ask the
group to focus on how to use teamwork to
solve a real-world problem. Ask learners how
they would approach the task of getting an
unwilling team member to buy into helping to
solve the assigned problem, even though he/
she may not be willing to do that. How would
they handle this dynamic?
Seventh Session: Assignment—Consider this as a
summary session. Have each learner prepare
and submit a summary of the main points
learned from the previous set of six virtual
exercises. Individuals should then each in turn
present the highlights that resonated with each
one and the reasons that it did. Facilitate a
robust discussion regarding these concepts
and welcome learner engagement. Summarize
the key points you, as the teacher, would like
to reinforce as conclusion and as a review.
Conclusion
In this section of the chapter, the authors have
attempted to outline concrete steps, which can be
taken to teach leadership and teamwork building
virtually. This is clearly a work in progress. The
seven sessions are a beginning that has proved
constructive but leaves much more that can be
done, especially within other cultural environments. There are already advanced degree programs on leadership that may be modied to the
surgeons purposes and utilized following the initial steps to start training leadership in a crosscultural context described in this second part of
our chapter.
References
1. Bass B, Bass R. The Bass handbook of leadership: theory, research, and managerial applications.
NewYork: Simon & Schuster; 2008.
2. Spaner SJ, Warkona GL. Brief history of endoscopy, laparoscopy, and laparoscopic surgery. J
Laparoendosc Adv Surg Tech A. 1997;7:369–73.
3. Asimov I, Shulman JA, editors. Isaac Asimov’s book
of science and nature quotations. NewYork: Grove
Press; 1990.
4. https://www.forbes.com/sites/forbescoachescoun-
cil/2021/12/09/tomorrows- ceos- are- shifting- fromheroic- to- humble/?sh=355279da2d31. Accessed on
5.15.2022.
5. https://www.cslewisinstitute.org/resources/pride-
and- humility/?gclid=EAIaIQobChMI9NqZzoqjAIVghXUAR2wJQCYEAAYAiAAEgLQqPD_BwE.
Accessed on 6.17.2022.
6. Steadman A.The military leader. Bloomington, IN:
Westbow Press; 2018.
7. www.paacs.org
8. Starzl TE.The puzzle people. Pittsburgh: University
of Pittsburgh Press; 2003.
9. Willink J, Babin L. Extreme ownership: how U.S.
navy seals lead and win. New York: St. Martin’s
Press; 2017.
10. Laeeq K.Video-based assessment of operative competency in endoscopic sinus surgery. Am J Rhin Aller.
2010;24:234–7.
11. https://www.facebook.com/groups/herniacollab/
about/
12. Prabhakaran K. Open tracheostomy for COVID19- positive patients: a method to minimize aerosolization and reduce risk of exposure. J Trauma.
2020;89:265–71.
13. Dhaliwal G. Teaching medicine to non-English
speaking background learners in a foreign country. J
Gen Intern Med. 2009;24:771–3.
How toOrganize andProvide ICU
https://t.me/medicina_free
Care inLow- andMiddle-Income
Countries
AnanyaAbateShiferaw, DeborahA.Haisch,
DawitKebedeHuluka, andDavidH.Chong
Some people want it to happen, some wish it would happen, others make it happen.
– Michael Jordan
19
Abbreviations
ER Emergency room
HICs High-income countries
ICU Intensive care unit
LMICs Low- and middle-income countries
SSA Sub-Saharan Africa
WHO World Health Organization
A. A. Shiferaw
Department of Anesthesiology, Addis Ababa
University College of health Sciences,
Addis Ababa, Ethiopia
D. A. Haisch
Pulmonary and Critical Care Division, Weill Cornell
Medical College, New York, NY, USA
e-mail: dah2020@med.cornell.edu
D. K. Huluka
Division of Pulmonary and Critical Care Medicine,
Department of Internal Medicine, School of
Medicine, College of Health Sciences, Addis Ababa
University, Tikur Anbessa Specialized Hospital,
Addis Ababa, Ethiopia
D. H. Chong (*)
Division of Pulmonary and Critical Care and Sleep
Medicine, CUNY School of Medicine, St. Barnabas
Health System/CUNY School of Medicine,
Bronx, NJ, USA
e-mail: dchong@sbhny.org
Introduction
Studies done in Africa show that the majority of
admissions to intensive care unit (ICU) are associated with surgical conditions such as sepsis from a
perforated viscous, multiple trauma, C-sections,
orthopedics, and neurosurgical procedures [1–3].
The World Health Organization (WHO) mandates
that ICU capacity be available in hospitals providing surgical services [4]. Postoperative patients,
who made up the majority of critical care admissions in ve sub-Saharan countries in a 2007 study,
were found to have the greatest survival benet
from an ICU admission, highlighting the importance of critical care for postoperative patients in
low- and middle-income countries (LMICs) [1].
Improving the availability and quality of critical care is essential for reducing the burden of
preventable deaths in LMICs [5]. Currently, the
overall high costs restrict access to ICU care in
LMICs. There exists an urgent need to develop an
affordable critical care model [5]. The substantial
proportion of critical care costs in LMICs are due
to stafng and xed equipment costs as opposed
to medication and laboratory testing costs [6].
The conventional high-income country model,
based on resource-intensive units with expensive
monitoring and life support equipment and large
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023
M. A. Hardy, B. R. Hochman (eds.), Global Surgery, https://doi.org/10.1007/978-3-031-28127-3_19
195
196
https://t.me/medicina_free
A. A. Shiferaw et al.
numbers of highly trained staff, is unlikely to be
an effective and sustainable model in LMICs settings [5].
Establishing Critical Care:
TheEthiopian Experience
Back in early 1990s, foreign anesthesiologists
established the idea of creating a surgical ICU
when the rst anesthesiology residency program
was started in Ethiopia at Addis Ababa
University. These anesthesiologists engaged
with hospital administration and other key
stakeholders and reached a consensus on a plan
to start and grow a critical care program. Using
a collaborative approach, a ward was created to
accommodate six patients located in close proximity to the operating room that eventually was
transformed into an ICU. The evolution to an
ICU included constructing a nursing station,
mounting monitors, and installing an infrastructure to connect oxygen tanks in a small room
next to the ICU. Donations were solicited for
the major essential ICU equipment; such purchases included four mechanical ventilators, six
patient monitors, and six suction machines.
Other equipment including a debrillator, and
intravenous pumps were procured. The foreign
anesthesiologists trained the anesthesiology residents and nurses, thus completing the ICU care
model. As the ICU progressed, the nurses and
the resident physicians gradually developed,
through supervision and training, the skills to
independently manage critically ill surgical
patients. The surgical ICU (SICU) program
helped advance the capabilities of a medical
ICU, which has been established earlier but
were not able to provide mechanical ventilation
support. Postgraduate residency training in critical care was expanded to other departments
such as internal medicine, surgery, pediatrics,
and gynecology as trainees came to the anesthesia managed SICU for a one- to three-month
rotations. The SICU also provided rotations of
other postgraduate students from all over the
country and provided an opportunity to participate in a critical care training. Over time, the
Ethiopian anesthesiology graduates grew to
supervise and lead the teaching service and to
they continue to expand critical care education.
The program continued to expand and to
strengthen, thereby improved the quality of critical care. This led to the development and creation
of a need-based adult critical care medicine curriculum. Invited foreign anesthesia faculty continued to visit for three-month rotations to deliver
hands-on skill training and up-to-date teaching,
in addition to virtual didactic lectures throughout
the year. Partner institutions provided resources
for faculty recruitment and helped cover travelrelated costs. The SICU continues to be a hub for
quality care and education for the SICU and other
departments as well as outside teaching institutions locally, nationally, and internationally to
advance critical care in all of Ethiopia and beyond
(especially in sub-Saharan Africa (SSA)). Due to
the high cost of ICU equipment and supplies,
critical care in Ethiopia and many other LMICs
continue to rely on foreign donations.
Pivoting toAddress COVID
inEthiopia
The Ethiopian COVID response included having
dedicated healthcare facilities and hospitals for
COVID care, repurposing non-health facilities
for COVID care, and devoting some health facilities to non-COVID essential services. The latter
required an isolation center for COVID cases to
stay until referral to a COVID treatment center or
until recovery. Finally, COVID ICUs were established to help care for the most critically ill; ICU
equipment like mechanical ventilators, monitors,
and suction machines were procured or were
obtained by donation specically for the COVID
response. Short-term ICU and COVID-specic
training was established for all healthcare professionals involved in all the COVID centers. The
COVID response increased the capacity of hospitals in terms of critical care service delivery
as compared to pre-pandemic time. Importantly,
COVID highlighted the need for more critical care capacity and training and has brought
much needed attention to these requirements for
19 How toOrganize andProvide ICU Care inLow- andMiddle-Income Countries
https://t.me/medicina_free
197
adequate healthcare delivery to the local leaders and to the regional and national leaders and
administrators.
What Does It Take toSet UpanICU
inLMICs?
The four major components that are vital to establish an ICU are (1) infrastructure, (2) equipment
and supplies, (3) education and training, and (4)
establishing best practice models. Related discussion may be also found in Chaps. 12 and 14
which address the use of different types of iCU’s.
(1) and(2) Infrastructure, Equipment
andSupplies
An ICU should have adequate space so that it can
accommodate the essential equipment for providing mechanical ventilation, monitoring, suctioning, and resuscitation. Even though it is difcult
to construct a new space in LMICs, it is possible
to identify and reconstruct adequate available and
appropriate space within a hospital setting.
According to international standards, there needs
to be a minimum, 12m2 peran ICU bed [7]. The
ICU should also be located close to the operating
theatres, or at least on the same oor, and relatively close to the radiology site, ER, and laboratory, if possible [7]. Easy means of patient
transport such as a dedicated hallways and/or an
elevator must be available whenever the ICU is
located farther from these essential areas.
Uninterrupted supply of electricity is mandatory for safe delivery of critical care [8]. LMICs
need to have a backup electricity system for ICUs
(such as generators or a backup battery system)
to protect patients for electricity interruption,
which is not uncommon in many LMICs.
Alternative sources of energy, like solar energy as
needed, should be considered. A protocol on how
to handle electricity interruptions must be put in
place [7, 8]. Availability of water is also essential
and challenging in most LMICs. Looking for
alternative sources of water and a water conservation strategy must be implemented to safely
deliver critical care. Hand hygiene infrastructure
and assurance of environmental hygiene is absolutely essential for safe ICU care in LMICs [8].
Finally, an adequate and consistent oxygen
supply is a crucial component of any ICU [8].
ICUs in LMICs need to choose the type of oxygen supply based on both availability and needs.
A plan to procure a sustainable supply to ensure
adequate oxygen delivery should be well developed and tested for efciency, before setting up
an ICU. A centralized distribution system for
oxygen is recommended wherever mechanical
ventilators are to be used [8].
Also ICU budgets and protocols should be
developed and rened to maximize resources and
focus on the purchase and maintenance (hospital
staff and/or contract with the company) of essential ICU equipment. Whether that equipment is
purchased or obtained by donation, maintenance
is of utmost importance. Trained biomedical engineers should be on site to help with machine troubleshooting and xing malfunctioning devices.
The ICU team should also be trained on how to
clean, utilize, and store equipment. Hospitals
should dedicate a budget for maintenance, training of staff, and purchase of machine accessories
such as ventilator circuits, monitor accessories,
etc. The ICU leadership should work very closely
with the hospital’s administration, the ministry of
health, and other stakeholders to assist with adequate resource allocation and planning.
A continuous education model for staff and
providers for best proactive protocols must be
provided. An education plan is essential for the
successful implementation and sustainability of a
successful ICU program.
(3) and (4) Education and Training,
and Interdisciplinary Best Practice
Models
Beyond the initial infrastructure and curriculum
components of building an ICU, leveraging
national and international resources can provide
key support to ongoing education and initial
research efforts in this context. These resources
can provide additional specialist training,
198
https://t.me/medicina_free
A. A. Shiferaw et al.
continuing medical education, mentorship,
instruction in the conduct of research, methodology for data collection, and opportunities for
development of collaborative interactions. An
interdisciplinary team composed of physicians,
surgeons, clinical pharmacists, gastroenterologists, internists, public health experts, nutritionists, nurses, and biomedical professionals should
be established to facilitate development of protocols for (1) the management of common ailments, (2) utilization of equipment, (3)
management of nutrition, (4) prevention and
management of infection, etc.; it is critical to
have regular planning and performance evaluation sessions to identify any gaps and to efciently address any issues to establish a best
practice model for delivery of ICU care.
Specialist Training Models
Multiple models for medical education have been
used to train specialists in countries without a
dedicated cadre of experienced staff on site. Most
use a combination of foreign faculty with that of
the local institution to develop an effective curriculum. Ideally, teaching should be on-site, but
there are varying degrees of ongoing in-country
training as well as in remote options.
One teaching model of an emergency medicine program was started with a initial needs
assessment invited by the Ethiopian Ministry of
Health’s taskforce, which was performed in collaboration with a partner institution. These data
included information about stafng, patient ow,
and logistics concerning the emergency department where all training was to occur; the data
also provided information on trainee education
prior to residency and the availability and usefulness of the existing educational infrastructure
including simulation, journal clubs, and bedside
teaching. Finally, other factors were identied
such as learner barriers and a needs assessment in
the context of the existing framework for the
learner environment. An assessment of disease
burden and a survey of trainee ability to manage
specic presentations was also considered. This
granular data led to the formulation of program
goals and of the resultant curriculum (including
content and delivery plans). The plan was developed by the partner institution, with an outside
visiting teaching attending physician invited for
threemonths per year to implement this curriculum, which focused on fullling the previously
formulated didactic and bedside teaching goals.
In addition, an iterative feedback process allowed
curriculum revisions after each month review,
when the visiting attending was present. This
feedback process eventually included “distancebridging initiatives,” including a formalized faculty-resident mentorship program and monthly
videoconferences.
Similarly, a dedicated 2-year pulmonary and
critical care fellowship training program (Eastern
Africa Training Initiative) was developed in
Ethiopia under the direction of one of the major
medical schools in Addis Ababa. As with other
programs, an initial needs assessment provided
critical data to design the next steps. This program included an agreement by the school of
medicine to recruit and pay fellow salaries, while
a group of external invited volunteer faculty who
would develop the curriculum and commit to be
on-site for 80% of teaching and supervision during the initial years of the program. Currently,
majority of the lectures are done remotely via
Zoom, and internal attendings include previous
graduates of the program. Additional training
beyond the clinical scope includes training in
research methodology (experimental design, data
collection, statistical evaluations, etc.). The program culminated with a month-long observership
in the United States at three major teaching hospitals to allow trainees to observe practices that
might not be standard in their local setting (e.g.,
interdisciplinary intensive care unit rounds with
respiratory therapy and nursing). This rotation
also helped create networking opportunities for
future collaborations. The program also helped
the rotating fellows create research opportunities
and the design an ICU database. Abstracts were
submitted with joint authorships to major international conferences, and funds were solicited
for fellows and attendings to attend and present
their research. Fellows were also asked to successfully pass American Board-type annual
examination to evaluate their and the program’s
effectiveness. To date, fteen specialists have
19 How toOrganize andProvide ICU Care inLow- andMiddle-Income Countries
https://t.me/medicina_free
199
been trained in adult and pediatric pulmonary
and critical care to serve throughout the region
and country. Many of the graduates have been
appointed to major hospitals throughout Ethiopia,
consistent with their previous agreements with
the Ministry of Health. Many are now leaders and
department chairs in their home institutions. Two
of those graduates are from other East African
nations, Tanzania and Rwanda, and went back to
their countries where they are actively serving
their communities.
A similar training approach has been applied
to other specialties and could also be applied in
areas such as respiratory therapy, as well as in
nursing. This type of approach to joint training
could be employed to advance an education
mechanism to implement high-quality intensive
care delivery.
Impact of National
andInternational Societies
Participation in regional and international professional societies and formation of relevant professional societies within countries may be important
not only for accessing continuing education and
research collaboration but may contribute signicantly to the coordination of efforts and to setting
public health agendas across regions and countries. The Society of Critical Care Medicine and
the European Critical Care Society have created
courses to help certify non-critical care practitioners to improve their care for these patients.
For example, during the COVID-19 pandemic, the Ethiopian professional societies
which previously focused on pulmonary and
critical care were the obvious source for muchneeded guidance for Ethiopia’s Ministry of
Health in creation of management guidelines
and ongoing education. The Ethiopian Thoracic
Society and others helped guide the ministry
with COVID management guidelines and
assisted nationally with policy changes to (1)
organizational structure; (2) record-keeping; (3)
stafng and human resource capacity; (4) training and curriculum programs and practice guidelines (for physicians and nurses); and (5) existing
relationships and collaborations, regionally and
nationally.
Critical Care Improves Outcomes
In 2015, Dr. Paul Farmer’s group conservatively
estimated that 4.8 billion people in the world had
no access to surgery. Ninety-ve percent of the
population in south Asia and central, eastern, and
western sub-Saharan Africa did not have access
to surgical care. In stark contrast, less than 5% of
the population in Australasia, high-income North
America, and western Europe lack access [9].
Approximately 16.9 million people die from conditions that require surgical care each year, the
vast majority of them in low- and middle-income
countries (LMICs) [10]. But even when patients
can get surgery, the perioperative mortality after
surgery is high, especially in Africa. The reasons
are numerous; patients in LMICs often present
late when the disease processes are more
advanced. In one study, 57% of operations were
for emergency indications, compared with around
25% emergency operations in cohorts from highincome countries (HICs) [11]. In the same study,
the patients that were routinely admitted to a
critical care unit immediately after surgery had a
2.4% mortality as compared to those who were
admitted to a critical care unit to treat subsequent
complications, which then led to a mortality
which was in excess of four times at 9.7%.
However, crucial resource challenges hamper the
safe delivery of surgical and critical care in
Africa. A quarter of hospitals do not have a reliable oxygen source, a third do not have reliable
electricity, 70% do not have pulse oximeters, and
47% do not have a dedicated postoperative or
critical care unit [12, 13]. In these studies in
LMICs, the average provider-to-population density of specialist surgeons, anesthetists, and
obstetricians was approximately thirty times
lower than the recommended global minimum.
The case for delay in expansion of surgical care
and critical care in LMICs is primarily nancial.
It may also be delayed by insufcient total number of trained physicians, and especially specialists, complicated by signicant “brain drain”
200
https://t.me/medicina_free
A. A. Shiferaw et al.
because of poor physician income compared to
that in HICs. Many essential surgical interventions such as C-sections, orthopedics, general
surgery, and even hydrocephalus surgery are very
cost- effective in resource-poor countries [14].
But the needs remain great. A 2020 review of
critical care in the African continent reported an
average of 0.3 ICU beds per 100,000 people [15].
A recent, on-the-ground study in Ethiopia conrmed only 0.3 public ICU beds per 100,000
populations [ 16]. Although higher than the rate
of 0.1 reported for Uganda, this is far lower than
the 8.9 previously reported in South Africa [17]
and inadequate to meet the needs of Ethiopia. In
contrast, the United States has 20–31.9 ICU beds
per 100,000 people [18].
Summary
This chapter briey summarizes the needs for
ICU care in LMICs, especially for trauma and
postoperative care to improve the overall survival outcomes. It addresses the stafng, the
construction, the equipment, and the leadership
required to establish well-functioning and effective ICUs in LMICs, using Ethiopia as an example. It also emphasizes the absolute need for
multi-specialist collaboration and the need for
specialist nurse training for the ICU to provide
optimal care. Self- evaluation and periodic audits
are needed to maintain and establish high standards of an ICU.
References
1. Towey RM, Ojara S. Intensive care in the developing world. Anaesthesia. 2007;62:32–7. https://doi.
org/10.1111/j.1365- 2044.2007.05295.x.
2. Okech UK, Chokwe T, Mung'ayi V.East Afr J Med.
2015;92(2).
3. Abebe K, Negasa T, Argaw F.Surgical admissions
and treatment outcomes at a tertiary hospital intensive care unit in Ethiopia: a two-year review. Ethiop
J Health Sci. 2020;30(5):725. https://doi.org/10.4314/
ejhs.v30i5.11.
4. World Health Organization. WHO, surgical care at
the district hospital; 2003. https://apps.who.int/iris/
bitstream/handle/10665/42564/9241545755.pdf;jsess
ionid=6FC140F238332BF9FC34289BEBA60C23?s
equence=1. Accessed 15 Aug 2020.
5. Turner HC, Van Hao N, Yacoub S, Hoang VMT,
Clifton DA, Thwaites GE, Dondorp AM, Thwaites
CL, Chau NVV. BMJ Global Health. 2019; https://
doi.org/10.1136/bmjgh- 2019- 001675.
6. Agrawal A, Gandhe M, Gandhe S, et al. Study
of length of stay and average cost of treatment in
medicine intensive care unit at tertiary care center. J Health Res Rev. 2017;4:249. https://doi.
org/10.4103/2394- 2010.199329.
7. Rungta N, Govil D, Nainan S, Munjal M, Divatia
J, Jani CK. ICU planning and designing in India –
guidelines; 2010.
8. Papali A, Schultz MJ, Dünserr MW. Recommendations on infrastructure and organization of adult ICUs
in resource-limited settings. Intensive Care Med.
2018;44:1133–7. https://doi.org/10.1007/s00134-
017- 4972- 0.
9. Alkire BC, Raykar NP, Shrime MG, Weiser TG,
Bickler SW, Rose JA, Nutt CT, Greenberg SL, Kotagal
M, Riesel JN, Esquivel M, Uribe-Leitz T, Molina
G, Roy N, Meara JG, Farmer PE. Global access
to surgical care: a modelling study. Lancet Glob
Health. 2015;3(6):e316–23. https://doi.org/10.1016/
S2214- 109X(15)70115- 4.
10. Shrime MG, Bickler SW, Alkire BC, Mock C.Global
burden of surgical disease: an estimation from the provider perspective. Lancet Glob Health. 2015;3(Suppl
2):S8–9.
11. International Surgical Outcomes Study group. Global
patient outcomes after elective surgery: prospective
cohort study in 27 low-, middle- and high-income
countries. Br J Anaesth. 2016;117:601–9.
12. Meara JG, Leather AJ, Hagander L, et al. Global
surgery 2030: evidence and solutions for achieving
health, welfare, and economic development. Lancet.
2015;386:569–624.
13. LeBrun DG, Chackungal S, Chao TE, etal. Prioritizing
essential surgery and safe anesthesia for the post-2015
development agenda: operative capacities of 78 district hospitals in 7 low- and middle-income countries.
Surgery. 2014;155:365–73.
14. Chao TE, Sharma K, Mandigo M, Hagander L,
Resch SC, Weiser TG, Meara JG.Cost-effectiveness
of surgery and its policy implications for global
health: a systematic review and analysis. Lancet Glob
Health. 2014;2(6):e334–45. https://doi.org/10.1016/
S2214- 109X(14)70213- X.
19 How toOrganize andProvide ICU Care inLow- andMiddle-Income Countries
https://t.me/medicina_free
201
15. Craig J, Kalanxhi E, Hauck S. National estimates
of critical care capacity in 54 African-countries.
medRxiv. Published online July 6, 2020. https://doi.
org/10.1101/2020.05.13.20100727. Accessed 3 June
2021.
16. Kie F, Boru Y, Tamiru HD, Sultan M, Walelign
Y, Demelash A, Beane A, Haniffa R, Gebreyesus
A, Moore J. Intensive care in sub-Saharan Africa:
a national review of the service status in Ethiopia.
Anesth Analg. 2022;134(5):930–7. https://doi.
org/10.1213/ANE.0000000000005799.
17. Dünser MW, Baelani I, Ganbold L. A review and
analysis of intensive care medicine in the least developed countries. Crit Care Med. 2006;34:1234–42.
18. Prin M, Wunsch H. International comparisons of
intensive care: informing outcomes and improving
standards. Curr Opin Crit Care. 2012;18(6):700–6.
https://doi.org/10.1097/MCC.0b013e32835914d5.
How toUse Surgical Ultrasound
https://t.me/medicina_free
inResource-Limited Settings
BethA.Schrope, ChristopherCassim,
ShamirO.Cawich, AyemoethuMa,
CatherineMcManus, RobbieA.Rampersad,
andRoshniRao
The very rst step towards success in any occupation is to become interested in it.
– William Osler
20
Abbreviations
ACR American College of Radiology
AIUM American Institute of Ultrasound in
Medicine
ATA American Thyroid Association
CME Continuing medical education
dB Decibels
FAST Focused abdominal sonogram for
trauma
FNA Fine-needle aspiration
MHz Megahertz
B. A. Schrope (*) · C. McManus · R. Rao
Department of Surgery, Columbia University Vagelos
College of Physicians and Surgeons,
New York, NY, USA
e-mail: bs170@cumc.columbia.edu;
cm3304@cumc.columbia.edu;
rr3181@cumc.columbia.edu
C. Cassim · R. A. Rampersad
Department of Radiology, Eric Williams Medical
Sciences Complex,
Champ Fleur, Trinidad and Tobago
S. O. Cawich
Department of Surgery, University of the West Indies,
St. Augustine Campus, Trinidad and Tobago
A. Ma
Department of Surgery, University of California, San
Francisco- East Bay, Oakland, CA, USA
TGC Time gain compensation
TI-RADS Thyroid imaging reporting data
system
USAID United states agency for interna-
tional development
USES UltraSound essentials for surgeons
W Watts
Background
Ultrasound Physics
andInstrumentation
Critical to optimal utilization of ultrasound in
clinical practice is a fundamental understanding
of basic ultrasound physics. What follows is a
concise review of the physical principles of ultrasound, correlated with practical applications to
hands-on imaging techniques, modalities, and
image interpretation. Finally, general recommendations for learning and practicing ultrasound are
provided. Specialty-oriented training is also covered in the organ system sections.
An acoustic wave is a longitudinal, mechanical wave travelling through a medium, with alternating compression and rarefaction (expansion).
Understanding the waves’ behavior is facilitated
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023
M. A. Hardy, B. R. Hochman (eds.), Global Surgery, https://doi.org/10.1007/978-3-031-28127-3_20
203
204
λ
v
f
-zer
pressure minimum
LONGITUDINAL
https://t.me/medicina_free
B. A. Schrope et al.
by a sinusoidal or transverse representation, with
energy (both positive, compression, and negative,
rarefaction) represented on the vertical axis and
time on the horizontal axis (Fig.20.1). Waves are
described by their wavelength, frequency, propagation velocity, amplitude, and phase.
Wavelength is dened as the distance a wave
travels per one complete cycle. Frequency is
inversely proportional to wavelength and is dened
as the number of cycles per second; 1 cycle/s is
1 Hz. Wavelength (λ, in meters) and frequency
(f, in Hertz) are related by the speed of sound (v,
meters per second) through a medium, which is a
variable that is specic to the medium itself:
=
The speed of sound through different biologic
soft tissues varies slightly, but for the purposes of
ultrasound imaging, an accepted speed used for
calculations is 1540m per second. For practical
purposes, a smaller wavelength, and thus a higher
frequency, results in better resolution or ner
detail in the nal image. Ultrasound is dened as
acoustic energy with frequencies higher than that
achievable with human hearing, about 20kHz.
Typical frequencies used in medical ultrasound
imaging are in the range of 2.5 to 20MHz. Note
though that for reasons to be discussed forthwith,
there are limitations on frequency selection that
preclude just selecting the highest frequency possible for best resolution.
There are several descriptors of wave magnitude: amplitude, power, and intensity. The amplitude of the acoustic wave, measured in decibels
(dB), corresponds to the amount of pressure in
the medium as the wave propagates. Power is the
amount of energy generated per unit time and is
measured in Watts (W). Intensity is the power
density within a given area and is expressed in W/
m2. In practical terms, these variables are manipulated by adjusting the power on the ultrasound
equipment.
Phase describes the temporal location in the
wave cycle and is measured in radians or degrees.
It is difcult to appreciate absolute phase in the
high frequencies of ultrasound, but the relationships between multiple waves can aid in interpretation of images. Two waves (incident and echo,
perhaps) that are 180 degrees out of phase, for
example, will cancel each other out.
With a basic understanding of the acoustic
wave properties, we are now able to explore the
behavior of the acoustic wave as it propagates
through the medium, which is the essence of
creating the image. Energy in any form is never
lost but simply transformed. As ultrasound waves
travel through a medium, they may be transmitted, refracted, reected, scattered, or absorbed
(Fig.20.2). Initially, an acoustic wave is gener-
Fig. 20.1 An acoustic
wave is a longitudinal
wave travelling through
a medium. It may be
represented by a
sinusoidal wave to more
easily understand its
properties
Propagation
WAVE
TRANSVERSE WAVE
o
Compression
Rarefaction
pressure maximum
Соседние файлы в папке @xirurgi_2025