Cop

Eur J Anaesthesiol 2013; 30:405–408

yr

FroDeGl

CoE-Pr

02

ORIGINAL ARTICLE

A simple epidural simulator

A blinded study assessing the ‘feel’ of loss of resistance in fourfruits

Diana Raj, Roy M. Williamson, David Young and Douglas Russell

CONTEXT Complex epidural simulators are now available,but these are expensive and not widely available. Simplesimulators using fruit have been described before.

OBJECTIVE To ascertain which easily available fruit wouldbest simulate the ‘feel’ of loss of resistance experienced inepidural insertion and be used as a teaching tool.

DESIGN A single blinded study using four different fruitshoused in a purpose-built box to conceal the identities of thefruits. The fruits were labelled A, B, C and D.

SETTING Two teaching hospitals in Glasgow, Scotlandbetween 2006 and 2007.

PARTICIPANTS Fifty participants consisting of consultantanaesthetists, specialist registrars and senior house officersall with previous epidural experience.

INTERVENTION Insertion of a Tuohy needle into the fourconcealed fruits (orange, banana, kiwi and honeydewmelon). Each participant then completed a questionnaire

ight © European Society of Anaesthesiology. U

m the Department of Anaesthesia and Intensive Care, Gartnavel General Hospital, Glpartment of Statistics and Modelling Sciences, University of Strathclyde, Glasgowasgow (DR), UK

rrespondence to Dr Diana Raj, MB, ChB, MRCP, FRCA, Gartnavel General Hospimail: diana.raj@ukgateway.netesented in part at the Annual Meeting of the Obstetric Anaesthetists’ Association i

This article is accompanied by the following Invited

Commentary:

Columb M. When comparing apples and oranges is

all bananas! Eur J Anaesthesiol 2013; 30:397.

65-0215 � 2013 Copyright European Society of Anaesthesiology

that included recording of the realism of the ‘feel’ of lossof resistance of each fruit.

MAIN OUTCOME MEASURES The ‘feel’ of loss of resist-ance for each fruit was scored on a 100-mm Visual AnalogueScale. A ‘0 mm’ represented ‘completely unrealistic feel’and ‘100 mm’ represented ‘indistinguishable feel from a realpatient’.

RESULTS A total of 62.6% of participants recorded thebanana as their first choice. This result was statisticallysignificant after taking into account the grades of theparticipants, their years of experience, the needle gaugeused and the participants’ chosen technique.

CONCLUSION The banana is a cheap and easily availabletraining tool to introduce novice anaesthetists to the feelof loss of resistance, which is best experienced before thefirst insertion of an epidural in a patient.

Published online 28 April 2013

Introduction

Lumbar epidural blockade is a commonly performed

procedure in anaesthesia. Junior anaesthetists tend to

gain their first experience of the technique of epidural

insertion in the obstetric population wherein almost one

in four labouring women requests an epidural.1 In a

survey by Wantman et al.,2 99% of obstetric and non-

obstetric lumbar epidurals within the UK were inserted

with Dogliotti’s technique3 of loss of resistance either

intermittently or continuously to 0.9% sodium chloride or

air. This technique depends on ‘feel’, which is difficult to

teach to novices without their hands on the needle, so for

most, the feel of the loss of resistance is appreciated

for the first time on a patient.

Epidural anaesthesia is not without its complications,

the incidence of which is higher among inexperienced

trainees.4 Any method of teaching trainees some idea

nauthorized reproduction of this article is prohibited.

asgow (DR), Department of Anaesthesia, Royal Alexandra Hospital, Paisley (RMW),(DY), Department of Anaesthesia and Intensive Care, Southern General Hospital,

tal, Glasgow, Scotland, UK

n Sheffield, UK, in June 2007.

DOI:10.1097/EJA.0b013e328361409c

Copyr

406 Raj et al.

Fig. 1

Front view of the epidural simulator.

of the feel of loss of resistance before they are exposed to

patients is therefore valuable. Various epidural simulators

have been developed over the years.5,6 Unfortunately,

these have limited availability and are expensive.

In addition, all the simulators may not be ideal for the

practice of all the available techniques. In the era of

three-dimensional computer simulation and other high

technology teaching methods, we investigated the use of

an innovative, inexpensive and low-technology epidural

simulator. There has been anecdotal evidence of fruit

being used for the purpose of epidural simulation.7,8

We present a blinded study carried out to establish the

best fruit for simulation of the feel of loss of resistance.

MethodThis study was discussed informally with a member of

our local ethics committee but because no patients or

patient information was involved, formal ethical approval

was not required. All participation was voluntary.

A frame (hereafter referred to as the ‘epidural simulator’)

measuring 55� 25� 14 cm, with a base 35 cm wide, was

constructed from chipboard. We stacked four equally

sized cardboard boxes, each with a circular hole in the

outward face, into the frame. The front of the epidural

simulator had a narrow strip of chipboard attached by a

hinge to the top of the frame with four holes reflecting the

holes in the boxes. Each of the holes was covered by two

layers of opaque tape, which acted as a false skin and

hid the identity of the fruit. The hinge at the top of

the epidural simulator enabled the narrow strip to be

released from the clasp at the bottom of the frame for the

purposes of changing the tape and ensuring that the fruits

remained flush against the tape (Fig. 1).

The back of the epidural simulator consisted of a remo-

vable piece of wood attached by clasps. This piece

of wood was fitted after all the boxes were closed with

the respective covers. The fruits were secured firmly in

place within the boxes by foam. The frame had a broad

base, which was clamped on to a sturdy surface. This

represented a patient sitting up in bed.

This was a single blind study because the fruits had to be

rotated and changed at regular intervals by the authors.

The fruits were chosen for their general availability, low

cost, differing textures and lack of a central hard core.

The four fruits were kiwi, banana, honeydew melon and

orange. We randomly allocated the fruits a letter A to D,

which corresponded with the holes of the epidural

simulator. We tried to ensure that we used fruits of the

same variety, country of origin and approximately the

same degree of ripeness. The fruits were all bought from

the same supermarket. They were rotated after every two

to three participants and the smaller and juicier fruits

(being the kiwi fruit and the orange) were changed

every four to five attempts. The banana was rotated

and changed every six attempts. The honeydew melon

ight © European Society of Anaesthesiology. UnEur J Anaesthesiol 2013; 30:405–408

was simply rotated and repositioned to expose untrau-

matised parts of the fruit.

Each participant completed a form detailing his or her

grade (consultant, specialist registrar or senior house

officer), years of experience (0 to 4, 5 to 9 or more than

10), needle gauge used (16G or 18G) and the participant’s

choice of 0.9% sodium chloride or air. The form also

contained four 100 mm Visual Analogue Scales (VAS) on

which 0 mm represented a completely unrealistic ‘feel’

and 100 mm represented a ‘feel’ which was indistinguish-

able from a real patient. We recruited anaesthetists of

all grades with established epidural experience from

two hospitals in Glasgow. Prior to their participation,

we informed each participant that it was a lumbar epi-

dural simulator so as to ensure similar angles of needle

insertion. We also reiterated that simply the ‘feel’ of loss

of resistance was being scored and not the feel of the

different layers of skin and ligaments. All participants

were free to opt out of participating in this study at any

time.

authorized reproduction of this article is prohibited.

Cop

A simple epidural simulator 407

Fig. 2

Sco

re

KiwiHoneydewBananaOrange

70

60

50

40

30

Interval plot of fruit scores95% CI for the mean

Results from the Visual Analogue Scale (mm) depicting the feel of lossof resistance from the four fruits in the study. CI, confidence interval.

Statistical analysis was carried out using Minitab version

15 (Minitab Inc., State College, PA) with a significance

level of 5%. The scores for each fruit were compared

using a repeated measures general linear model, which

consisted of the grade of assessor (consultant, specialist

registrar or senior house officer), years of experience (0 to

4, 5 to 9 or more than 9), gauge size (16 gauge, 18 gauge)

and technique (0.9% sodium chloride air). Comparisons

between fruits were made using the Bonferroni correc-

tion factor.

ResultsFifty anaesthetists (29 consultants, 12 specialist registrars

and nine senior house officers) completed the study. The

anaesthetists were free to choose their normal epidural

technique and their preferred method of loss of resist-

ance. Thirty-four anaesthetists chose a 16 gauge (Sims-

Portex, Kent, UK) Tuohy needle. Of these, 27 (79%)

used 0.9% sodium chloride in the loss of resistance

syringe; the remaining seven used air. Sixteen anaes-

thetists used an 18 gauge needle. Fourteen (88%) of

these used 0.9% sodium chloride and two used air.

The data from the study are shown in Table 1. The

mean VAS scores and 95% confidence intervals for the

fruits are shown in Fig. 2.

There were no significant differences between fruits

chosen by grade of anaesthetist (P¼ 0.505), experience

(P¼ 0.640), needle gauge (P¼ 0.794) or technique

(P¼ 0.751). There was a significant difference between

the realism of the fruits (P< 0.001), with the banana

having the highest ratings. The results of the paired

comparisons are shown in Table 2. There were no

significant differences between the honeydew melon

and banana, the kiwi and honeydew melon or the orange

and kiwi.

DiscussionThe banana emerged as the most realistic fruit for simu-

lating the feel of loss of resistance, and is a very cheap and

easy makeshift simulator for every anaesthetic depart-

ment. We now encourage our junior trainees to practise

yright © European Society of Anaesthesiology. U

Table 1 Visual Analogue Scales (mm) for each fruit in the categories of

Orange Ban

All anaesthetists 38.8 (22.4) 62.6Grade

Consultant 42.1 (21.5) 64.6Specialist registrar 29.3 (19.1) 58.8Senior house officers 41.1 (27.8) 61.3

Needle gauge

16 gauge 39.1 (23.6) 63.718 gauge 38.3 (20.2) 60.5

Loss of resistance technique

0.9% sodium chloride 37.2 (23.7) 63.4Air 43.2 (15.1) 59.0

Values are mean (SD).

on bananas to ascertain the feel of ‘loss of resistance’ prior

to their first epidural insertion in a patient. The honey-

dew melon came a close second with the kiwi and the

orange placed third and fourth, respectively. There was

consensus among all the grades for the first and second

places of the banana and the honeydew melon.

Consultants, however, considered that the orange should

be placed third, in contrast to the trainees, who gave the

kiwi fruit third place.

There are some problems inherent in this study. The

most important issue was the inability to ensure

the constant state of ripeness and thus consistency of

the fruits. To alleviate this problem, we bought all the

fruits from the same supermarket and made sure of

the consistency of their variety and country of origin.

Only one author was designated purchaser of the fruits on

all occasions to ensure some uniformity and the fruits

used in the study were always freshly purchased.

nauthorized reproduction of this article is prohibited.

grades of anaesthetist, needle gauge used and technique practised

ana Honeydew melon Kiwi

(20.2) 52.1 (21.5) 44.1 (22.5)

(19.6) 50.4 (22.2) 42.9 (22.0)(25.2) 53.2 (23.0) 43.8 (23.1)(16.1) 56.2 (18.8) 49.1 (25.4)

(17.3) 50.0 (20.8) 46.5 (21.5)(25.9) 57.0 (23.0) 39.4 (24.7)

(20.4) 53.9 (20.9) 44.5 (22.2)(20.4) 44.4 (24.1) 43.0 (25.3)

Eur J Anaesthesiol 2013; 30:405–408

Copyr

408 Raj et al.

Table 2 The statistical analysis of comparisons between all thefruits in pairs adjusted using the Bonferroni method

Comparison

Mean

difference (mm) 95% CI P valueM

Honeydew-banana �10.5 (�21.8 to 0.8) 0.08Kiwi-banana �18.5 (�29.7 to �7.2) <0.001Orange-banana �23.7 (�35.0 to �12.5) <0.001Kiwi-honeydew �8.0 (�19.2 to 3.3) 0.36Orange-honeydew �13.2 (�24.5 to �2.0) 0.01Orange-kiwi �5.3 (�16.5 to 6.0) 1.00

CI, confidence interval. M Adjusted.

All these steps, however, may have not been adequate to

ensure the consistency in texture, which was a crucial

factor in the comparison process.

Second, 82% of participants used the loss of resistance

to 0.9% sodium chloride as their technique of choice.

The infusion of 0.9% sodium chloride into the fruit

posed two additional problems: fluid shift within the fruit

due to osmotic forces and the waterlogging that changed

the ‘feel’ of the fruits, leaving them ‘boggy’. The

honeydew melon posed a different problem because

the 0.9% sodium chloride that was infused pooled in

the central core, thereby altering the feel and risking a

simulated dural tap! The banana had the least problems

with waterlogging. We circumvented this problem by

changing the fruits frequently.

Third, with regard to the blinding of the whole process,

some of the fruits had very distinct scents and many

participants did manage to identify the fruit, which may

have led to some bias in the results.

Fourth, we used the VAS because such a scale is mainly

used to measure a characteristic or opinion across

a continuum wherein a precise value is not directly

measurable. This has been most widely validated in

the assessment of pain, but has been used previously

for measuring participants’ perception of realism in a

simulation setting.9,10

There are only a few reports in the literature relating to

the realism of epidural simulator devices, despite the

presence of a number of these devices on the market.

Anderson et al. tested a force-feedback simulator for

realism using a 7-point scale (in which 1¼not realistic

ight © European Society of Anaesthesiology. UnEur J Anaesthesiol 2013; 30:405–408

and 7¼ extremely realistic).6 The average score for the

feel of the procedure in their study was 4.8 which, when

converted to a percentage, equated to 68.6%. This score

is not much higher than the mean VAS score of 62 mm

obtained for the banana in our study. It is regrettable that

such simulators are released on to the market without any

objective measurement of their realism. We suggest that

the VAS may form an easily reproducible way of assessing

the realism of many simulator devices in future studies.

We have shown that a banana can be a cheap and easily

acquired simulator for the purpose of teaching the feel of

loss of resistance for epidural insertion. This may improve

safety profiles among junior anaesthetists.

AcknowledgementsAssistance with the study: the authors would like to thank

Mr Samuel Frickleton Small for his invaluable contribution in

the manufacture of the epidural simulator and all the participating

anaesthetists from the Victoria Infirmary and the Southern General

Hospital, Glasgow.

Financial support and sponsorship: none declared.

Conflicts of interest: none declared.

References1 Burnstein R, Buckland R, Pickett JA. A survey of epidural analgesia for

labour in the United Kingdom. Anaesthesia 1999; 54:634–640.2 Wantman A, Hancox N, Howell PR. Techniques for identifying the epidural

space: a survey of practice amongst anaesthetists in the UK. Anaesthesia2006; 61:370–375.

3 Dogliotti AM. A new method of block anesthesia. Segmental periduralspinal anesthesia. Am J Surg 1933; 20:107–118.

4 Paech MJ, Godkin R, Webster S. Complications of obstetric epiduralanalgesia and anaesthesia: a prospective analysis of 10995 cases. Int JObstet Anesth 1998; 7:5–11.

5 Dang T, Annaswamy TM, Srinivasan MA. Development and evaluation of anepidural injection simulator with force feedback for medical training. StudHealth Technol Inform 2001; 81:97–102.

6 Anderson BD, Macgill JC, Anderson GB, et al. A novel epidural simulator.Anesthesiology 2003; 99:A538.

7 Cloote AH, Parke TJ, Kinsella SM. An analysis of three different loss ofresistance techniques using the ‘greengrocer’s’ epidural simulator. Int JObstet Anesth 1995; 4:182–183.

8 Leighton BL. A greengrocer’s model of the epidural space. Anesthesiology1989; 70:368–370.

9 Price DD, McGrath PA, Rafii A, Buckingham B. The validation ofvisual analogue scales as a ratio scale for chronic and experimental pain.Pain 1983; 17:45–56.

10 Devitt HD, Kurrek MM, Cohen MM, Cleave-Hogg D. The validity ofperformance assessments using simulation. Anesthesiology 2001;95:36–42.

authorized reproduction of this article is prohibited.