Petroleum Jelly as an Alternative Coupling
Medium in Focus Assessed Transthoracic Echocardiography (FATE)
C Smit* and A Breedt*
Department of Anaesthesiology and Critical Care, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa
Submission: November 15, 2021; Published: March 04, 2022
*Corresponding author: C Smit, Department of Anaesthesiology and Critical Care, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa, ORCID: https://orcid.org/0000-0002-8168-6416
A Breedt, Department of Anaesthesiology and Critical Care, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa, ORCID ID: https://orcid.org/0000-0002-5242-3684
How to cite this article: C Smit, A Breedt. Petroleum Jelly as an Alternative Coupling Medium in Focus Assessed Transthoracic Echocardiography
(FATE). J Anest & Inten care med. 2022; 11(5): 555825. DOI 10.19080/JAICM.2022.11.555825
Background:The use of ultrasound gel as a coupling medium has been the standard of practice for all ultrasound studies performed at most hospitals worldwide. This study aimed to introduce petroleum jelly [petrolatum] as an alternative coupling agent, specifically with regard to focus assessed transthoracic echocardiography [FATE], by comparing its use to conventional ultrasound gel.
Methods:A crossover, double-blinded, non-inferiority study was conducted to ascertain whether petroleum jelly scores equal to ultrasound gel in terms of image quality [depth, penetration, detail, and overall quality] and user experience [pressure applied, amount of gel used, user friendliness, and patient tolerance] using a General Electric [GE] Vscan Extend handheld ultrasound [HHU] device. The automated ejection fraction calculation was also noted and statistically compared.
Results:No significant difference was found between image quality or user experience in FATE scans performed with the conventional ultrasound gel and petroleum jelly. The automated ejection fraction calculation results obtained from scans with petroleum jelly showed minimal inter-user variability. Blinded sonographic review also did not rate the images obtained with either coupling medium significantly different in any measure. Finally, petroleum jelly is more cost effective than conventional ultrasound gel.
Conclusion:Petroleum jelly produces images of comparable quality to that obtained using conventional gel. The use of petroleum jelly as an alternative coupling medium could increase the practice of ultrasound in settings with resource limitations.
Keywords:ultrasound, echocardiography, point-of-care, critical care
Sonography has become a vital clinical tool in resource-limited settings due to reduced cost, increased patient comfort, ease of portability, real-time diagnosis capability, and lack of ionizing radiation . The World Health Organization (WHO) has described ultrasound as an effective, safe, versatile and low-cost clinical modality . One of the largest global healthcare organizations, Partners in Health, has studied the use of ultrasound in low-resource settings and found this modality to be a helpful skill that is teachable and “a critical component in global health delivery” . Throughout the world, point-of-care ultrasound has proven to be an ideal imaging modality in rural and resource-limited countries. Clinical predictive capability is made easier for most clinicians, including for anaesthetists, through modalities such as transthoracic echocardiography (TTE). Focus assessed transthoracic echocardiography (FATE), which is a TTE protocol that focusses on obvious pathologies, provides important diagnostic information that changes perioperative patient management. The FATE protocol principally aims to exclude obvious cardiac and pleural pathologies . Moreover, perioperative case series reports, and multiple clinical studies have shown that FATE can prevent adverse events and have a direct clinical impact on patient mortality [5-7], which is why several academic societies now advocate focused TTE as a mandatory skill for critical care physicians [8,9].
Image acquisition, however, needs to be precise, and the correct views must be obtained in a short amount of time, all of which is contingent upon user experience and, importantly, the coupling medium used. Indeed, using an appropriate coupling medium is crucial in ultrasonography to improve the conduction
of the ultrasound waves between the probe and the patient’s tissue
. Limited access to ultrasound coupling gel in low-resource
settings can significantly hamper the clinical application of FATE.
This study aims to introduce petroleum jelly as a cost effective and
readily available alternative coupling medium.
The primary objective of this study was to compare petroleum
jelly to conventional ultrasound gel as an alternative coupling
medium during FATE by having medical staff at the Faculty of
Medicine and Health Sciences at Stellenbosch University rate the
quality of the petroleum jelly-and conventional gel-based images,
as well as their user experience whilst scanning an anatomical
model. Secondarily, the automated ejection fraction calculation
during each scan and the clinical acceptability of the images
obtained using both mediums was assessed and compared by
having an expert echocardiographer blindly review the images.
Lastly, the cost effectiveness of using petroleum jelly instead of
conventional gel was also calculated and compared.
Following review and approval from the Stellenbosch
University Health Research Ethics Committee (ref #S21/03/039),
a double-blinded, non-inferiority trial was performed using
participants from the medical staff from the Department of
Anaesthesiology and Critical Care, Faculty of Medicine and Health
Sciences, Stellenbosch University. This specific sample population
was chosen as medical personnel from this department uses
FATE daily for critical patient care and perioperative patient
evaluation and would benefit the most by the research being conducted. All participants performed FATE scanning on an
anatomical model with a clinically normal cardiac anatomy
using a handheld ultrasound device (GE Vscan Extend). This
handheld ultrasound (HHU) device is a digital smart device that
gives specific instructions on how to perform a FATE scan using
an application called “Scan Coach”. These user instructions
give specific information regarding the probe positioning for
every view that needs to be obtained during the FATE scan. The
participants were blinded, mediums unlabelled, and the sequence
of mediums used randomised using a computer program. A scanprotocol
was completed by participants for each coupling medium
individually. The study participants acquired images that were
then saved and uploaded onto the device. The participant was able
to access reference ultrasound images of a normal anatomy and
examples of common pathologies for each scanning plane whilst
performing the FATE scan. Furthermore, the participant could
also review 3D animations that showed the relationship between
the probe positioning and resulting ultrasound images, with
annotated schematics of the anatomical landmarks to acquire the
The LVivo EF application on the GE Vscan Extend HHU was also
utilized during each scan to calculate the ejection fraction using a
modified Simpson’s method. This application does automatic edge
detection of the left myocardial wall with use of apical 4-chamber
views to calculate the end-diastolic volume, end-systolic volume,
and ultimately the ejection fraction. The participants were asked
to score the ultrasound images obtained from the two separate
scans on a 5-point Likert scale in terms of 7 criteria (Table 1) (See
The images obtained during every scan were also evaluated
blindly by a cardiac physiologist using a Likert scale. An image
pair was compared individually for each image parameter. Images
were scored out of 10 in terms of image quality, depth, and
penetration, and whether the image could be used clinically or not
During digital evaluation, a grayscale tablet was used to
evaluate the echo density in the muscle areas and echo-free areas
in multiple regions of interest of each image (Figure 1). Muscular
areas appear whiter on the scale and blood appears darker. A
difference of 3 or more tones indicates an artifact and the quality
of an image was judged by the number of artifacts present.
Statistical analysis was done using Microsoft Excel® (Microsoft
Corp, Redmond, WA, USA). and IBM SSPS Statistics Version 25 
and was based on a mixed linear model. Participants as well as the
reviewer completed a digital online questionnaire. All data was
collected and processed using RedCap (Research electronic data
capture) software  hosted by Stellenbosch University.
A paired means power analysis of the 2x2 crossover design
was done using Design and Analysis of crossover trials by Jones
and Kenward [12,13] that estimated a power of 82% using a
sample size of 34 from a population of 45 with an alpha of 0.05
and a beta of 0.17836. This would detect a mean paired difference
of 1.0 with an estimated standard deviation of 4.5 and with a
significance level (alpha) of 0.05 using a one-sided paired t-test.
We set our non-inferiority margin as a difference of less than 1
unit (20%) on the respective Likert scales used. Discussions with
clinicians and radiologists revealed that a difference of more than
1 unit on a 5-point Likert scale would be clinically significant. As
the variance was unknown beforehand, we calculated a sample size that would be more than adequate to prove non-inferiority
and were able to recruit 37 participants.
The automated ejection fraction obtained during each scan
was recorded using an Excel spreadsheet, and a chi-squared
McNemar’s test was done using the binomial distribution to
determine whether the inter-user variance obtained met the set
standard of 5% .
Data was collected over a period of 8 weeks at the Department of
Anesthesiology and Critical Care (DACC), Stellenbosch University.
All participants met the inclusion criteria: medical staff members
from the Anesthesiology department and surgical Intensive Care
Unit who had never used petroleum jelly as a coupling medium
during FATE ultrasound. The participant group consisted of 28
doctors from the DACC and 9 doctors from the Intensive Care Unit;
this included 7 consultants, 21 registrars, and 9 medical officers,
respectively. From this group, 7 had 3–5 years of experience with
FATE ultrasound, 15 less than 3 years, and 15 little to none.
The rating of the overall image quality for images obtained
using petroleum jelly as the coupling medium compared to the
rating of the overall image quality for images obtained using
traditional ultrasound gel amongst participants was non-inferior:
paired mean diff.(participants) = -0.16 (95% CI: -0.65; 0.33) (Table2). In comparison, the radiological reviewer found that the images
obtained from petroleum jelly were statistically superior in terms
of detail (p=0.04) as well as depth and penetration (p=0.04),
however not clinically superior as the paired difference did not
exceed a value of one unit (Table 3).
experience whilst comparing the two mediums from the questions
asked. Both mediums were comparatively easy to use; paired mean
difference = 0.06; 95% CI (-0.59; 0.48). Relatively similar amounts
of both mediums were used for either scan; paired difference = 0.32; 95% CI (-0.77; 0.73). The average amount of pressure
applied during each scan with either medium was also similar;
paired mean difference =0.24 (-0.24; 0.72). There was, however,
a statistically significant assessment that conventional ultrasound
gel is better tolerated by the patient than petroleum jelly; paired
mean difference=-0/22; 95%CI (-0.41; -0.04) (p=0.02).
Conventional ultrasound gel is purchased by Tygerberg
Hospital from Health and Beyond suppliers at R11.31 per 250
mL bottle and white petrolatum at R7.50 per 250 mL jar .
Approximately 2–5 mL of conventional gel as well as petroleum
jelly was used, respectively, on average among participants to
perform a scan, which would mean that petroleum jelly use would
save this institution R3.81 per bottle, 10 cents per mL, and 50
cents per scan.
The inter-user variability for ejection fraction determination
during scans done using ultrasound gel and petroleum jelly were
both found to be 1%. Using petroleum jelly during automated
ejection fraction determination is thus comparable to using ultrasound gel and meets the criteria for acceptability considering
a set acceptable inter-user variability of 5% .
The sonographic reviewer was asked at the end of each
evaluation to ascertain whether the images from the individual
scans could be deemed “clinically usable” in their opinion.
A Chi Squared McNemar’s test of independence was performed
and showed no significant association between the coupling
medium used and the determination of clinical acceptability by
the sonographic reviewer; (p=1) meaning that the exact same
percentage of scans using petroleum jelly were deemed clinically
usable to make a clinical diagnosis as were using conventional
ultrasound gel (29.7%).
Although ultrasound is an increasingly necessary and useful
diagnostic tool, most resource-limited settings do not have the
adequate funding for this technology nor the necessary coupling
mediums to make use of this resource. In most urban and large
hospital settings, commercial ultrasound gel is used for this
purpose. Unfortunately, the availability of commercial ultrasound
gel in low-resource settings is scarce and usually expensive.
Commercial ultrasound gel is manufactured locally but needs to
be imported in most other parts of Africa. For many rural and
deprived communities, the cost and availability of ultrasound
gel imposes a significant constraint on the quality and number
of scans that are available to clinicians, even in settings where
reliable ultrasound scanners are available . Moreover, the
gel that needs to be imported is sold at a higher price locally due
to inclusion of importation duties and profits that local vendor
make from procurement. Although these expenses might seem
trivial in a developed country where resources are abundant, in
an impoverished setting, this expense is far too big and one of the
first of the clinical resources to be sacrificed.
These costs are invariably transferred to the patients that make
use of health facilities and places extra financial constraints on
health departments. Furthermore, for the sake of gel conservation,
some establishments have gone as far as to ration the amount
of coupling medium used for a scan to inadequately small
amounts, which compromises the quality of the scans . These
developments are indeed very alarming, especially considering the
high mortality and morbidity reported in deprived communities
in trauma and obstetric cases, where ultrasound is a cornerstone
of clinical management and patient treatment . Thus, a need
exists for alternative coupling mediums A multitude of alternatives
to commercial gel have been suggested and tried, unfortunately with limitations and severe paucity in the literature—olive oil
being expensive and unavailable in most settings, corn-starch
having a manufacturing process that is complex and expensive,
and the suggested WHO recipe of ethylenediaminetetraacetic,
trolamine, propylene glycol, and carbomer being difficult to source
and producing poor images .
A study by Engelbrecht and Palma in 2015  showed that
petroleum jelly could be used as a coupling agent for ocular
ultrasound in an Emergency Department. However, Engelbrecht
and Palma reported solely that the petroleum jelly did not damage
the ultrasound probe, so there are no comparative data regarding
the quality of the ultrasound images obtained with the respective
This study clearly demonstrates that using petroleum jelly
as a coupling medium produces sonographic images that are
comparable and non-inferior to those produced by conventional
ultrasound gel. Image quality was not negatively affected using
petroleum jelly as a coupling medium, as proven by the blinded
participants as well as a blinded reviewer. Participants also found
petroleum jelly comparatively easy to use, with no difference in
amount of pressure applied during the scan using equal amounts
of both coupling mediums. Although patient tolerance showed
a comparatively statistically significant difference, a clinically
significant difference could not be proven. Inferential analysis of
the automated ejection fraction calculation obtained during scans
using either medium show that the calculation obtained from scans
using petroleum jelly as a coupling medium showed an acceptable
inter-user variability of less than 5% , a result identical to the
variability amongst calculations using conventional ultrasound
gel. Lastly, the blinded sonographic reviewer deemed the same
ratio of scans clinically acceptable from the pooled scans using
either of the mediums.
There is no evidence in the literature regarding the effect
of petroleum jelly on ultrasound probes. This study was also
conducted in a single center. Furthermore, performing and rating
an ultrasound image depends on the subjective opinion of the
sonographer, which can vary according to experience and personal
bias towards the coupling medium used. Finally, ultrasound is a
highly dynamic investigation, which can be very user dependent.
Petroleum jelly is an inexpensive, widely available, simpleto-
use resource that produces images of similar quality to
that of conventionally produced ultrasound gel. As we have
formally demonstrated the non-inferiority of petroleum jelly in
comparison to conventional ultrasound gel in FATE ultrasound,
the ideal is to promote the use of this medium in settings that are
resource-limited, attempting to increase the capacity for the use
of ultrasound for diagnostic purposes, screening, and monitoring,
as well learning.