Introduction
Many cases of infection and death have been reported due to the coronavirus disease
2019 (COVID-19) pandemic. As of January 2021, more than 85 million cases of infection
have been confirmed and the number of deaths has surpassed 1.8 million worldwide.
COVID-19 can develop in individuals infected by severe acute respiratory syndrome
coronavirus 2 (SARS-CoV2), which is an RNA virus that belongs to the broader family
of coronaviruses. The viruses that caused severe acute respiratory syndrome (SARS)
and Middle East Respiratory Syndrome (MERS) were also coronaviruses [1]. SARS-CoV2 is thought to be transmitted mainly by contact infection and droplet
infection, but the precise mechanisms are unknown. Recent reports have suggested the
possibility of aerosol infection, and thus, more careful infection control measures
are considered necessary [2]
[3]
[4]. Wearing masks and disinfecting the hands are effective for preventing infection,
and medical institutions are also implementing various infection control measures.
There is currently no established treatment, but the effectiveness of various antiviral
drugs has been reported [5]
[6]. Vaccine development is being carried out all over the world, and further development
is expected in the future [7]
[8]
[9]
[10]
[11]
[12].
Endoscopic procedures carry a risk of infection because there is a risk of exposure
to the patient’s respiratory secretions and digestive juices. For this reason, many
academic societies have proposed infection control measures for endoscopic procedures
[13]
[14]
[15]
[16]
[17]. When performing endoscopy, it is necessary for endoscopists to wear adequate personal
protective equipment (PPE), disinfect their hands, and clean the endoscopy room. In
addition to these steps, new steps for infection control that shield patients and
prevent the spread of contaminants are considered necessary.
Many cities around the world have been placed on lockdown to slow the spread of the
COVID-19 pandemic, which has had serious economic consequences. The pandemic has also
affected endoscopic practice, making it difficult to perform conventional endoscopic
examinations [18]
[19]. In response, we are developing the new “Shielding Device for Endoscopic Procedures”
as part of the Save the Endoscopy Project (STEP by STEP). Here, we report the current
status of the project and report a preliminary evaluation of the feasibility and utility
of STEP.
Patients and methods
Device description
We are developing STEP in collaboration with Olympus Medical Systems Co., Ltd. and
an otolaryngologist. STEP consists of a mask ([Fig. 1a]) worn by the patient and a tubular drape ([Fig. 1b]) that covers the endoscope. On the side of the mask, there is a small hole for air
inflow and a suction port for suction of aerosols generated by the patient. The drape
connects to a hole at the tip of the mask and the endoscope is inserted into the drape.
There is also a valve-like structure in the hole that prevents droplets from escaping
when the patient coughs.
Fig. 1 STEP (“Shielding Device for the Endoscopic Procedures”). a Mask part, b drape part, and c endoscope before the examination. The drape was taped to the base of the endoscope
(yellow arrow). d Simulated endoscopy using STEP. A suction tube was connected to the mask (red arrow)
and aerosols generated from the patient were continuously sucked. e Simulated endoscopy using STEP. The mask part covered the patient’s nose and mouth.
How to use
The use of STEP is shown in [Fig. 1c], [Fig. 1d], [Fig. 1e]. First, the endoscope is inserted into the tubular drape, which is then taped to
the base of the endoscope. After pharyngeal anesthesia, the mask is placed on the
patient’s face and the patient is positioned in the left lateral position as usual.
The suction tube is attached to the suction port. Next, the tip of the tubular drape
is connected to the hole in the mask. The endoscopist operates the endoscope through
the vinyl tubular drape. Because the endoscope is located inside the tubular drape
and mask, the endoscopist does not come into direct contact with the patient’s saliva
or digestive juices. When the endoscopic procedure is completed, the endoscope is
stored inside the tubular drape and the tubular drape is detached from the mask.
Given that the hole in the mask has a valve-like structure, it is difficult for droplets
inside the mask to escape. The contaminated endoscope remains in the tubular drape
while it is transported to the washing room.
Experiment
In this study, we conducted experiments to investigate the feasibility and utility
of STEP in the upper gastrointestinal endoscopy.
For the feasibility study, we used an EVIS Lucera Elite Gastrointestinal Videoscope
(GIF-H290Z; Olympus Medical Systems Corp., Tokyo, Japan) and an upper gastrointestinal
endoscopy training model (LM-103; Koken Co., Ltd., Tokyo, Japan). Three endoscopists
performed a total of 18 endoscopic examinations on the training model, alternating
between using and not using STEP. The endoscopic examination was performed on the
pharynx, the upper middle and lower esophagus, and the stomach. The stomach was observed
by the screening method proposed by Yao et al. [20]. Then, the duodenal bulb, descending portion, and Vater’s papilla were observed.
The procedure time from insertion to removal was compared between the groups using
and not using STEP. In addition, three endoscopists who were blinded to the study
evaluated endoscopic images of the pharynx/esophagus, the body of the stomach in the
retroflex position, the body of the stomach in the straight position, the antrum of
the stomach, and the duodenum. The images were evaluated using a visual analog scale
(VAS), with scores ranging from 0 (“not observed at all”) to 100 (“completely observed”).
For the utility study, we created models simulating contact, droplet, and aerosol
infection.
In the simulated contact infection model, 20 mL of indigo carmine pigment was sprayed
throughout the stomach of the training model. Then, the three endoscopists, who were
wearing white gloves, performed the above-mentioned examination ([Fig. 2]). The ratio of the area of the pigment attached to the white gloves (the area of
the attached pigment / the total area of the glove × 100) was measured using image
J.
Fig. 2 Simulated contact infection model. After spraying indigo carmine pigment into the
training model, the endoscopist put on a white glove and performed an endoscopic screening
examination. The proportion of the area of the white glove to which the indigo carmine
pigment was attached was measured.
In the simulated droplet infection model ([Fig. 3]), a sheet of paper was hung on a wall 10 cm in front of a sprayer installed in the
mouth of a polystyrene foam head model, and 0.2 mL of India ink was sprayed [21]. The paper onto which the India ink was sprayed was then imaged and binarized to
divide each pixel into black and white. The experiment was performed three times under
the same conditions and the average number of black pixels was compared between trials
using and not using STEP.
Fig. 3 Simulated droplet infection model. A sprayer was installed in the mouth of the head
model (yellow arrow) and ink was sprayed. The paper onto which the ink was sprayed
was imaged, and the number of pixels that became black after binarization was measured.
In the simulated aerosol infection model [22]
[23], an airway management training model (AirSim Advance Bronchi X; TruCorp., Lurgan,
UK) and an electronic cigarette (FLEVO; GIEX, Tokyo, Japan) were used ([Fig. 4]). The airway management training model was placed inside a plastic case to create
a stable environment. The vaporized liquid from the electronic cigarette was sprayed
from outside the plastic case as a simulated aerosol for 0.9 seconds and then injected
into the respiratory tract through a tube. Using a particle counter (MET ONE HHPC
6 + ; Beckman Coulter, Brea, California, United States), the total number of particles
0.3 to 10 μm in size was measured for 120 seconds. The experiment was performed three
times under the same conditions and the average total number of particles was compared
between trials using and not using STEP. In the trials using STEP, suction was performed
from the suction port of the mask with a pressure of −40 kPa and a flow rate of 40 L/min.
Fig. 4 Simulated aerosol infection model. The airway management training model was placed
inside the plastic case and the vaporized liquid from an e-cigarette was sprayed through
a tube from outside the plastic case (yellow arrow). The number of aerosol particles
diffused into the plastic case was measured with a particle counter (red arrow).
Statistical analysis
Data were analyzed using the unpaired t-test, Chi-squared test, Fisher’s test, or
Mann-Whitney U-test as appropriate. P < 0.05 was considered significant. All statistical
analyses were performed using SPSS version 20 (SPSS IBM statistics).
Results
A total of 18 endoscopic procedures were performed using STEP without problem. The
procedure time was 126.3 ± 11.6 seconds with STEP and 122.3 ± 10.0 seconds without
STEP; no significant difference was observed between the two groups. The VAS scores
for the evaluation of endoscopic images taken in the STEP group were as follows: pharynx/esophagus,
91.7 ± 9.0; body of the stomach in the retroflex position, 91.2 ± 9.2; body of the
stomach in the straight position, 88.5 ± 12.3; antrum of the stomach, 91.0 ± 9.5;
and duodenum, 91.0 ± 11.3. The VAS scores for the non-STEP group were as follows:
pharynx/esophagus, 90.9 ± 9.3; body of the stomach in the retroflex position, 91.1 ± 8.8;
body of the stomach in the straight position, 87.7 ± 13.7; antrum of the stomach,
90.9 ± 9.0; and duodenum, 91.7 ± 10.4. The results were equivalent for the STEP and
non-STEP groups ([Table 1]).
Table 1
Results of the feasibility study
|
STEP group
(n = 9)
|
Non-STEP group
(n = 9)
|
P value
|
|
Procedure time, s ± SD
|
126.3 ± 11.6
|
122.3 ± 10.0
|
N.S.
|
|
VAS score
|
|
|
|
|
All images
|
90.7 ± 10.1
|
90.4 ± 10.0
|
N.S.
|
|
Pharynx/esophagus
|
91.7 ± 9.0
|
90.9 ± 9.3
|
N.S.
|
|
Body of stomach in retroflex position
|
91.2 ± 9.2
|
91.1 ± 8.8
|
N.S.
|
|
Body of stomach in straight position
|
88.5 ± 12.3
|
87.7 ± 13.7
|
N.S.
|
|
Antrum of stomach
|
91.0 ± 9.5
|
90.9 ± 9.0
|
N.S.
|
|
Duodenum
|
91.0 ± 11.3
|
91.7 ± 10.4
|
N.S
|
Data are shown as the mean ± standard deviation.
STEP, ; N.S., not significant; VAS, visual analog scale.
In the contact infection model, the proportion of the area of the white gloves onto
which the indigo carmine pigment adhered was 4.9 ± 1.4 % in the non-STEP group and
0 % in the STEP group.
In the droplet infection model, the number of pixels that became black after binarization
was 351 418 ± 90 735 in the non-STEP group and 0 in the STEP group.
In the aerosol infection model, the average total number of particles in the plastic
case was 346 837 ± 9485 in the non-STEP group and was significantly reduced to 222 ± 174
in the STEP group ([Table 2]).
Table 2
Results of the utility study
|
STEP group
(n = 3)
|
Non-STEP group
(n = 3)
|
P value
|
|
Contact infection model
Proportion of area of the white glove to which the indigo carmine pigment adhered
(% ± SD)
|
0
|
4.9 ± 1.4
|
P < 0.05
|
|
Droplet infection model
Number of pixels that became black after binarization (pixels ± SD)
|
0
|
351 418 ± 90 735
|
P < 0.05
|
|
Aerosol infection model
Total number of particles in the plastic case (number ± SD)
|
222 ± 174
|
346 837 ± 9485
|
P < 0.05
|
Data are shown as the mean ± standard deviation.
SD, standard deviation.
Discussion
Endoscopic procedures, especially upper gastrointestinal endoscopy, carry a risk of
contact, droplet, and aerosol infection, and thus appropriate infection control measures
are required. Current infection control consists of the following three steps: before
the procedure, the endoscopy staff disinfects their hands; during the procedure, the
endoscopy staff wears PPE; after the procedure, the endoscopy staff cleans the endoscope
and endoscopy room and disinfects their hands [24]. However, once contaminants are diffused by coughing or vomiting, it is difficult
to completely clean and disinfect objects they come into contact with. Therefore,
these three steps are considered to be insufficient as infection control measures.
It is necessary to shield the patient in order to prevent as much as possible the
spread of contaminants to the surrounding environment. Accordingly, we have developed
the STEP shielding device for endoscopic procedures.
Several methods for shielding patients during endoscopy have previously been reported
[25]
[26]
[27]
[28]
[29]
[30]
[31], including a transparent plastic box and a vinyl sheet, both of which cover the
patient. However, these devices need to be cleaned and disinfected if they are reused.
Therefore, disposable items are desirable and we developed a solution consisting of
a disposable mask and drape. In addition, it was considered that the operability of
the endoscope may deteriorate when the patient is covered with a shield during the
procedure. We were similarly concerned that STEP might also affect the operability
of the endoscope. However, although the upper gastrointestinal endoscopy took several
seconds longer when using STEP, no significant difference was observed between the
STEP and non-STEP groups. In addition, the evaluation of endoscopic images produced
nearly identical results between the STEP and non-STEP groups. It was considered that
the effect of STEP on the operability of the upper endoscopy was minimal.
The primary purpose of shielding is to prevent contact with droplets from the patient’s
mouth and nose. However, saliva and digestive juices attached to the endoscope can
also be a source of infection. STEP’s tubular drape is attached to the endoscope and
prevents direct contact with saliva and digestive juices. In addition, given that
the endoscope can remain inside the tubular drape while being carried to the washing
room, it is possible to prevent contamination of the surrounding environment and medical
staff after the examination. In other words, STEP can play an important role not only
during but also after the endoscopic procedure. In this experiment, there was zero
contact with simulated contaminants in the STEP group in both the contact infection
and droplet infection models. Endoscopic procedures are also considered to pose a
risk of aerosol infection. COVID-19 can be spread by aerosol infection as well as
contact and droplet infection. To prevent aerosols from spreading, a suction port
was added to the mask. Continuous suction during the procedure significantly reduced
the amount of simulated aerosols released into the surrounding environment.
This study has several limitations. First, it is unclear how many droplets and aerosols
are generated during actual endoscopic procedures and how infectious they are. In
this experiment, an electronic cigarette was used as a simulated aerosol, but there
are no data on aerosol generation in clinical practice. In the future, we plan to
measure droplets and aerosols the clinical setting and investigate the extent to which
they can be contained by STEP. Second, if the patient’s oxygen saturation level drops,
it is necessary to remove the mask and apply a nasal cannula for supplemental oxygen.
At this time, the patient might cough or sneeze and spread droplets and aerosols.
Therefore, nasal cannulas should be applied before the start of the procedure when
administering sedative agents. In addition, it is considered important to monitor
the oxygen saturation level during an endoscopic procedure performed with STEP. It
is expected that the patient might feel some discomfort from wearing the mask during
the procedure. Moreover, saliva and vomiting may also collect in the mask, which an
increase the patient’s discomfort and affect the breathing. Therefore, before introducing
STEP into clinical practice, we plan to prospectively evaluate patient discomfort
and oxygen saturation level. Third, STEP’s tubular cover may affect the operability
of the endoscope slightly. In this experiment, no significant difference was observed
between screening endoscopy performed with and without STEP, but it is necessary to
investigate whether STEP affects operability when used in therapeutic endoscopy. Finally,
major issues are cost and the question of whether to use STEP for all examinations
and treatments or for only patients at high risk of infection. It is also important
to evaluate the time required to prepare and dispose of the STEP when introducing
it into clinical practice. Therefore, it will be necessary to evaluate the advantages
and disadvantages of STEP, including its cost and time.
Conclusions
In this study, we developed STEP in collaboration with Olympus Medical Systems Co.,
Ltd. and an otolaryngologist. When using STEP, the operability of the upper gastrointestinal
endoscope and the quality of the obtained endoscopic images were equivalent to the
conventional method without STEP. In addition, the use of STEP made it possible to
reduce the spread of contaminants in simulated models of contact, droplet, and aerosol
infection, suggesting that STEP may be useful for infection control in upper gastrointestinal
endoscopy.
