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NON
CARDIAC TRANS THORACIC
ULTRASONOGRAPHY IN SLOTH BEARS-Bear’s-BLUE

Abstract

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As
like the Trans abdominal ultrasonography examination technique used to examine
the visceral organs in the abdominal cavity; this non cardiac-trans thoracic ultrasonography
technique will help
to examine the lung
which is located inside the thoracic cavity of all mammals. The lung is the
only organ in the body always filled with air normally. The ancient belief was that the lung is
not optimal for ultrasonography imaging because the aerated lungs creates insurmountable obstacles.
So, people concentrated more on Trans abdominal, Trans rectal and Trans thoracic echo
cardiography and
the same got well established in human medicine and it got gradually adopted in veterinary
practice too. Thus, the ultrasonography examination of pulmonary system remains
as a grey area. But the advanced development in medical science broken the impossible and
proved that the
ultrasonography is a
excellent diagnostic modality in all mammalian species. Rantanen NW was the first
Veterinarian who used the
ultrasound technique
to diagnose pulmonary diseases in horse and successfully diagnosed pneumothorax
in 1986. After that more
awareness happened in the field, resulted in development of Bed side Lung
Ultrasound Examination (BLUE) protocol and Vet-BLUE protocol establishment in human
and small animal veterinary medicine respectively. But these advanced
technologies are not effectively utilized or further established in wild animal
medicine as it was in small
animal veterinary practice globally except in few research institution and teaching universities.
So, adopting those advanced diagnostic procedure is sine qua non for providing
ultimate care in captive wildlife.   In this article we clearly documented the
examination of pulmonary system of sloth bears by adopting non cardiac trans thoracic
ultrasonography technique which include patient preparation, positioning, probe selection and
also recorded the ultrasonography
image of normal as well as abnormal lung and also  radiograph
of lung with
interpretation for better understanding. Thus, we developed BLUE protocol for bears
(Bear’s-BLUE). The aim of this article is to disseminate the knowledge of bear’s lung
ultrasonography practice to wildlife veterinarians at field level and also encourage
the neophytes to adopt this practice and improve their diagnostic ability for
providing better care to the animals which are under care by making effective
therapeutic plan accordingly.

Key words:
Bear’s-BLUE, Lung ultrasonography, Trans thoracic ultrasonography, Sloth bear, Wild life,  Pulmonary system.

1. Introduction

The
classical belief was that the lung is not optimal for ultrasonography imaging,
this overriding belief perpetuate lung ultrasound’s delayed use in human and veterinary medicine.  So, people concentrated more on Trans abdominal, Trans rectal
and Trans thoracic echo cardiography and the same got well established
in human medicine and it
got gradually adopted in veterinary practice too thus, the ultrasonography examination of pulmonary
system remain as a grey
area. But the recent advanced development in medical science eliminated those
impossible huddles and proved that the ultrasonography is a excellent diagnostic modality in all species including
humans. Lung ultrasound has higher sensitivity than lung auscultation and
supine chest radiography for many acute and potentially life-threatening
respiratory conditions in people2,5,13,24,28. Rantanen NW was the first
Veterinarian who used the ultrasound technique to diagnose pulmonary diseases
in horse and successfully diagnosed the pneumothorax in 198623, followed this; same technique used to describe the
Pneumothorax in human medicine. Roy Philly dubbed the ultrasound probe as ‘modern
stethoscope’ in 1988. Thus
the remarkable foresight made unbelievably few decades ago. In 2011,
Moor dubbed the ultrasound probe the “visual stethoscope” because lung ultrasound artefacts are
objectively and clearly discernible independent of patient or ambient noise. In
2008 ,Thoracic FAST
called TFAST was first
standardized abbreviated ultrasound exam of the thorax in small animals that
include the chest tube site for lung surveillance for detection of pneumothorax(PTX)17 .The
recently established Vet-BLUE19,20,  the regionally –based lung ultrasound exam protocol for small
animals(dog & cats) further enhanced the utilization of lung ultrasound to
examine the complete pulmonary system and finding the all kinds of lung pathology such as lung oedema,
consolidation, pleural effusion and pneumothorax. The Vet BLUE consists totally
8 regional sites(4 on each side),which are /include the caudodorsal lung lobe region(Cd),the perihilar
lung lobe region(Ph), the middle lung lobe region (Md), and the cranial lung
lobe region (Cr).Though the lung ultrasound procedure is well established in smalls animals and equine
medicine, it’s not
much adopted in wild animal medicine due to various reason including restraining  issues to lake of knowledge to implement the same in different species .However little
information about lung ultrasonography in wild animals is documented22,
there is no much information about the same particularly for sloth bears which belongs to
family Ursidae . Hence
the authors took efforts to implement those existing advanced lung
ultrasonography techniques with few modifications in sloth bears to examine the
normal lung & lung
pathology as well and
documented the same in the name of Bear-BLUE protocol.   

2. Materials and Methods

The
study was carried out at Agra Bear Rescue Facility (ABRF), which is the home for 190
rehabilitated dancing sloth bears and managed by Wildlife SOS (a non-profitable
NGO) at Agra, Utter
Pradesh, India. Since, these bears were rescued from the street performers with poor health and
undergoing rehabilitation at ABRF; providing the maxim possible veterinary care by adopting recent
advancement in the field of veterinary medicine is an absolute must to diagnose
and treat the conditions as well as stabilize the health of those animals. The sloth bears are more
prone for various kind of pulmonary disorders, range from pneumonia to pulmonary tuberculosis.
Hence, the Lung
ultrasound is superior and less time consumable than chest radiography, we adopted lung
ultrasonography procedure for the evaluation of pulmonary system in sloth bears
as mentioned below

 

2.1 Patient preparation

However
the wild animals are under captivity for long time, their behaviours are not
much predictable, so choosing proper restraining method plays a pivotal role in
implementing any diagnostic producers
in animals such as sloth bears. By considering the safety of the veterinarian,
animal keepers and instruments we performed
chemical immobilization by using xylazine + ketamine to achieve hassle free restraining and also implement the
diagnostic procedure effectively to examine the lungs. The immobilized bear was
kept in supine position on the table. The hairs
on each side hemithorax
were trimmed by using hair clipper to get a better quality image by making perfect cupping
between probe and the skin after the application of ultrasound gel. The long
fur and dust on the fur coat will
create interference/disturbance for the ultrasound beam penetration. All the necessary
locations;4 zones in each side for
examinations were marked in
each side of hemithorax28 as mentioned in the figure.

2.2 Organ Anatomy

The
exact knowledge of organ anatomy and its topography is more essential for the
sonographer to proceed the
diagnostic techniques efficiently and quickly within the stipulated time. In
the absence of such anatomic knowledge or past experience, identification of pathologic changes may
not always be possible.  The lung anatomy
of the bears
resembles as close as
to human lungs. The multi
lobulated lung (2 lobes on right + 3 lobes on left + one
mediastinal lobe) located inside the thoracic cavity and poses well
developed visceral and partial pleura.so we fallowed lung ultrasonography
examination and nomenclature as described by the previous authors in human15
and small animals19,20  with slight
modification.

2.3 Instrument & Probe selection

Selection
of good quality
ultrasound machine which has compatibility with the phased array, curved linear and linear
probes is a prerequisite for getting enhanced performance. (probe pic)

We
used GE logq-E
machine and all the above
mentioned probes and the images were recorded to understand better. However,
the image quality differs based on the probe. The high frequency linear probe we used to evaluate the
pleural line/visceral-parietal pleural interface (VPPI) and pneumothorax, as
this probe has higher resolution. The low frequency curved linear and phased
array probe were used to diagnose Alveolar interstitial syndrome (CHF/ARDS),
pleural effusion, consolidation, pulmonary oedema and pneumonia, as this probe has better penetration than the high
frequency linear probe.

2.4 Probe orientation

Cranio –caudal
(probe marker towards head) is the standard orientation consisted of the observation of the previously
described “gator sign (alligator)” represented by two rib heads (the gator’s
eyes) with an interposed intercostal space (gator’s bridge of nose) likened to
a partially submerged alligator (gator) peering over the water at the
sonographer3,19 (Fig. ).This can also
be  called as a “Bat sign”15.

2.5 Ultrasound modes

The
commonly used ultrasound modes in lung ultrasonography is “B mode” and “M mode”.

Ø  B-Mode, or Brightness
Modulation, is the display of 2D map of B-Mode data, and is the most common
form of ultrasound imaging. Unlike A-Mode, B-Mode is based on brightness with
the absence of vertical spikes. Therefore, the brightness depends upon the
amplitude or intensity of the echo.

Ø  M-Mode
, or Motion Mode (also called Time Motion or TM-Mode), is the display of a
one-dimensional image that is used for analysing moving body parts commonly in
cardiac and foetal cardiac imaging. This can be accomplished by recording the
amplitude and rate of motion in real time by repeatedly measuring the distance
of the object from the single transducer at a given moment. The single sound
beam is transmitted and the reflected echoes are displayed as dots of varying
intensities thus creating lines across the screen.

The
typical M-mode imaging of normally aerated lung look like Sky-ocean-Beach
(linearity on top and granularity on bottom) but Lung with pneumothorax or
consolidation will reveal barcode sign (complete linearity in both top and
bottom) or “stratosphere ” appearance.The M-mode also helps in record the “Lung
point”10. The Lung Point is the position along the thorax where collapsed
lung recontacts the chest wall. The finding of the Lung Point increases the
sensitivity of Pneumothorax .

2.6 Artifact analysis/interpretation

Basic principles of lung ultrasound
in acute respiratory conditions generally centre around the observation of
ultrasonographic artifacts based on the dry lung (A-lines with a glide sign or
lungsliding) versus wet lung (ultrasound lung rockets or B-lines) concept. At the surface of the lung, the
prominent element is air. Its acoustic impedance is 0.0004 3 105 gp/cm2
s 26, which is very different
from that of bone (7 3 105 gp/cm2 
s), parenchyma (1.65 3 105 gp/cm2 . s), and water (1.48 3 105
gp/cm2 . s). The movement of the lung toward the chest wall is
characteristic. The ribs are identifiable by their acoustic shadow, Between two
ribs, a hyperechogenic line, behind which only airy artifacts are present, is
always visible14.The inability of ultrasound to penetrate air
–filled structures precludes its use for the examination of normal lungs, thus
ultrasounds image is herein exclusively composed of artifacts, but in disease
states where the normally air –filled lung is collapsed, consolidated  or replaced by fluid or mass lesions, ultrasound
waves can penetrate the thorax and the examination may provide valuable
information to complement the radiographic findings.

Skill in lung ultrasonography obviates the need for
most radiographs and CTscans in helping physicians to diagnose pleural
effu-sion, interstitial syndrome, and pneumothorax7.The diagnosis of
alveolar consolidation has been in practice for many years,and the ultrasound
signs are now standardized9.

Ø  A-lines: Equidistance, horizontal, repetitious lines below
pleural line .The Normal aerated lungs always produce A-lines (A=Air Artifact=Normal
lung).A lines are horizontal reverberation atifacts indicating a normal lung
surface.

Ø  Glide sign/ lung
sliding: 
Is a to and fro dynamic of the pleural line; its also can be called as
‘lung wall interface’14, indicating movement of the visceral pleura
past  the parietal pleura from the
respiratory craniocaudal excursion of the lung.

Ø  B-lines
: Vertical, hyper echoic rays projecting from pleural line(ring down artifact)1
, extend to the bottom of screen without fading as like a laser beam  and oscillate in synchronization with
inspiration and expiration3,8,13,18,19,23,28 .
Presence of B-lines always suggests sub pleural interstitial edema / wet lung6,12,18.
B-lines (lung rockets) are vertical reverberation artifact / comet tail
artifact29. Ultrasound lung rockets are thought to be the
radiographic equivalent of Kerley B-lines12,13,25. The number of
ultrasound lung rockets(ULRs) and the distance between each lung rockets is
directly correlates with the degree of lung edema in humans8,11,12,21,25,28
.When the ULRs blend into one another becoming confluent is called as
‘white lung’ and mentioned as ‘infinity-?’

Ø  Z-lines: It is vertical comment tail artefact but
differ from B-lines .Because they are less echogenic than the pleural lines,
ill defined, usually taper off at after 2to 4 cms, not erasing the A-lines and
not moving with lung sliding12.

Ø  O-lines: The
possible pattern of O line is absence
of any horizontal or vertical artefact. A slight movement of the probe often
brings out A-lines. This pattern should be considered having the same meaning
as of A-line12 .

Ø 
Air  bronchograms : These
are  punctiform  or 
linear  hyper echoic  artifacts 
within  the  consolidation. Dynamic
air bronchogram was the term used for the centrifugal inspiratory dynamic of
air bronchograms . Movement 1mm was required. Alveolar consolidation was
defined as an image yielding two signs. The first sign is a tissue-like image
arising from the pleural line or the lung line plus tissular behavior of this
image with no dynamic in the depth-surface axis. The second is the shred sign,
which is a shredded deep border of the tissular image, as in a connection with
aerated lung13. Both
signs yield 90% sensitivity and 98% specificity for the diagnosis of alveolar consolidation9.

3. Result & 
discussion

Zone
1,2,5 and 6 is suitable area for examination of pneumothorax in supine position
, zone 3,4 ,7 and 8 is suitable for plural effusion diagnosis because air
lighter than fluid so air always settled on top ,fluid  will settle at down. All the zones are
suitable to examine for any lung pathology like lung oedema, consolidation,
pneumonia and other nodular lesions due to carcinoma or tuberculosis. Small
surface probes of 3.0 and 3.5 MHz were quite suitable for this application, but
2.5-, 5-, and 7.5-MHz probes were equally effective4 . Our findings
of the normal lung pattern which is characterized by roughly horizontal,
parallel lines(A lines) and  Alveolar interstitial
syndrome yields roughly vertical, parallel lines(B lines ) is co inside with
finding of Lichtenstein D (1997)4.In the over 5400 extant mammalian
species, a wide variety of anatomic features have evolved, making knowledge
gained on one species not always applicable to another in a straightforward
manner. The ideal, which is still lacking for many species, is to have a clear
anatomic picture of the species involved before attempting to apply
ultrasonography. The vast differences among species dictate the selection of
ultrasonography technique to be applied and the quality of images obtained22.
.

4. Conclusion

The simplicity and high feasibility of
ultrasound makes it an attractive and easy-to-use diagnostic tool at the
bedside for lung ultrasound examination .so it has to be to incorporated as an
integral part of diagnosis for  the  intensivist as well as in  routine health evaluation protocol in bears.
Unlike other regions (heart, intra-abdominal organs), the surface of the lung
can be easily visualized using ultrasound. “The artifact” was quickly detected.
A simple portable unit (without Doppler) was sufficient.  The skill needed to recognize “the artifact”
was easily learned. Lung ultrasonography’s utility has been confirmed
by a growing number of studies and is simple to perform, provided one thinks
differently27

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