Analysis of Cricoid Pressure Forceand Technique Among Anesthesiologists,Nurse Anesthetists, and Registered Nurses

Melissa Lefave, DNP, APRN, CRNA, Brad Harrell, DNP, APRN, ACNP-BC, CCRN,

Molly Wright, DNP, APRN, CRNA

Purpose: The purpose of this project was to assess the ability of anesthesi-

Melissa Lefave,

Nurse Anesthesia T

versity, Jackson, T

CCRN, Clinical As

Loewenberg Colle

Wright, DNP, APR

thesia Track in the

son, TN.

Conflict of intere

Address corresp

Dr., Brownsville, T

� 2016 by Ame

1089-9472/$36.

http://dx.doi.org

Journal of PeriAnesth

ologists, nurse anesthetists, and registered nurses to correctly identify

anatomic landmarks of cricoid pressure and apply the correct amount

of force.Design: The project included an educational intervention with one group

pretest-post-test design.Methods: Participants demonstrated cricoid pressure on a laryngotra-

cheal model. After an educational intervention video, participants were

asked to repeat cricoid pressure on the model.Findings: Participants with a nurse anesthesia background applied

more appropriate force pretest than other participants; however, post-

test results, while improved, showed no significant difference among pro-

viders. Participant identification of the correct anatomy of the cricoid

cartilage and application of correct force were significantly improved af-

ter education.Conclusion: This study revealed that participants lacked prior knowledge

of correct cricoid anatomyand pressure as well as the ability to apply cor-

rect force to the laryngotracheal model before an educational interven-

tion. The intervention used in this study proved successful in educating

health care providers.

Key Words: cricoid pressure, nurse, anesthesiologist, nurse anesthetist,

Sellick’s maneuver, cricoid anatomy.

� 2016 by American Society of PeriAnesthesia Nurses

CRICOID PRESSURE, OFTEN termed ‘‘Sellick’smaneuver,’’ is used for the prevention of regurgi-

tation of gastric contents during induction of

DNP, APRN, CRNA, Associate Professor,

rack in the School of Nursing Union Uni-

N; Brad Harrell, DNP, APRN, ACNP-BC,

sociate Professor, University of Memphis

ge of Nursing, Memphis, TN; and Molly

N, CRNA, Chair & Professor, Nurse Anes-

School of Nursing Union University, Jack-

st: None to report.

ondence to Melissa Lefave, 130 Woodland

N 38012; e-mail address: mlefave@uu.edu.

rican Society of PeriAnesthesia Nurses

00

/10.1016/j.jopan.2014.09.007

esia Nursing, Vol 31, No 3 (June), 2016: pp 237-244

anesthesia or during positive-pressure ventilation.This technique was described by Sellick1(p405) in

1961 as ‘‘backward pressure of the cricoid carti-

lage against the bodies of the cervical vertebrae.’’

Sellick, however, was the not the first to consider

the advantages of such a maneuver. William

Cullen2(p16) in 1774 wrote, ‘‘whether the blowing

in is done by a person’s mouth, or by bellows, Dr.

Munroe observes, that the air is ready to pass bythe gullet into the stomach; but that this may be

prevented, by pressing the lower part of the larynx

backwards upon the gullet.’’ In 1776, Hunter3(p419)

described how the larynx could be gently pressed

against the esophagus and spine while ‘‘blowing

air into the lungs’’ to ‘‘prevent the stomach and in-

testines being too much distended by the air.’’

237

238 LEFAVE, HARRELL, AND WRIGHT

Despite sporadic reports that cricoid pressure may

not be as effective as once thought, the ‘‘Sellickma-

neuver’’ remains an accepted practice that is used

worldwide.4-8 One author9(p94) even suggests that

the omission of cricoid pressure in patients withknown or suspected risk factors of aspiration

would be unethical ‘‘until there is conclusive evi-

dence to suggest otherwise.’’

Patients at Risk for Pulmonary Aspiration

Induction of anesthesia may cause gastroesopha-

geal contents to enter the pharynx and tracheal-

bronchial passages, leading to a life-threatening

aspiration.10 Although aspiration of gastric con-

tents accounts for only 3.5% of all anesthesia

malpractice suits, it is a major source of anesthesia

morbidity.11 When deciding on candidates forcricoid pressure, it is prudent to identify those at

a greater risk of regurgitation and pulmonary aspi-

ration because of pathology or physiology

(Table 1). Such persons have pre-existing factors

that may lead to the presence of gastric contents.

Table 1. Patients at Increased Risk ofRegurgitation and Pulmonary Aspiration1,2

Severe trauma

Parturient . 14-wk gestation

Hiatal hernia

Gastroesophageal reflux disease

Diabetes mellitus

Gastroparesis

Extremes of age

Increased intra-abdominal pressure

Obesity

Abdominal ascites

Gastrointestinal obstruction

Ileus

Difficult intubation

Patient who does not meet NPO criteria for anesthesia

, 8 h since heavy meal

, 6 h since light meal

, 2 h since clear liquid intake

Neurologic factors

Glasgow Coma Scale , 8

Parkinson disease

Multiple sclerosis

Bulbar palsy

Myotonia dystrophica

Cerebrovascular accidents

Increased intracranial pressure

Narcotic administration

NPO, nothing by mouth.

Undetermined gastric volume, gastrointestinal

dysfunction, and altered lower esophageal

sphincter tone are among indications for the utili-

zation of cricoid pressure during rapid sequence in-

duction of anesthesia or during positive-pressureventilation.12

Anatomy

The cricoid cartilage is a complete ring of hyaline

cartilage just inferior to the thyroid cartilage (ie,

Adam’s apple).13 Identification of correct cricoid

cartilage anatomy is crucial to the success ofcricoid pressure and prevention of pulmonary

aspiration. The thyroid prominence should be

visualized on the front of the neck. It is the most

prominent protuberance midline. During palpa-

tion of the thyroid prominence, movement of the

finger caudally (toward the patient’s feet) will iden-

tify a drop into the cricothyroid notch or mem-

brane. The next horizontal structure is thecricoid cartilage.14

Although the efficacy of cricoid pressure has been

debated, Rice et al15 confirmed Sellick’s 1961 pro-

posal that ‘‘cricoid pressure compresses the

conduit between the stomach and the pharynx

as intended.’’ However, the authors further empha-

size that cricoid pressure does not occlude theesophagus, as the esophagus does not lie behind

the cricoid cartilage. Rice et al15 state that cricoid

pressure compresses the anterioposterior diam-

eter of the hypopharynx.

Force

The degree of cricoid pressure force is an impor-tant element to consider. Too little force leaves

the airway susceptible to the possibility of regurgi-

tation and ensuing aspiration. Excessive force has

been documented to worsen the laryngeal view,

causing difficulty with laryngoscopy and even pul-

monary ventilation.16 Furthermore, rupture of the

esophagus has been reported after active vomiting

during the application of cricoid pressure.5

The optimal force of application of cricoid pressure

has been debated before it came into common use.

Sellick merely suggested that ‘‘firm’’ pressure be

applied without obstructing the patient’s airway.1

Wraight et al17 recommended the initial force of

44 Newtons (N) from a study of 24 elective

Figure 1. Life-sized adult airway model on an

EBSA-20 infant scale. This figure is available in color

online at www.jopan.org.

CRICOID PRESSURE FORCE AND TECHNIQUE 239

anesthesia cases in 1983. In 1999, Vanner and

Asai18 recommended 10 N for the conscious pa-

tient increasing to 30 N once unconscious. A gen-

eral consensus of 30 to 40 N is now accepted to

generate adequate pressure to occlude the esoph-agus and prevent gastroesophageal regurgita-

tion.9,19

Technique

A single-handed or double-handed technique can

be used for cricoid pressure. Furthermore, two

or three fingers can be used to exert pressure.When using two fingers, the provider places the

cricoid cartilage between the first and second fin-

gers applying downward force. The three-finger

technique stabilizes the cricoid cartilage between

the thumb and third finger with the index finger

applying force.

Purpose

Cognitive and clinical application deficits exist

among health care providers in the performance

of cricoid pressure. Improper and inconsistent

application may increase the patient’s risk forregurgitation and subsequent aspiration of gastric

contents. The clinical implications associated

with improperly applied cricoid pressure warrant

evaluation of the cognitive knowledge and applica-

tion technique of providers. The purpose of this

project was to assess the ability of perioperative

hospital personnel (anesthesiologists, nurse anes-

thetists, and registered nurses) to correctly iden-tify appropriate anatomic landmarks of cricoid

pressure and apply the correct amount of force.

The researcher aimed to alert health care providers

of incorrect practice and to evaluate further educa-

tional needs among various groups of providers.

Furthermore, post-test data allowed for evaluation

of the educational instrument.

Design

This study was an educational intervention with a

group pretest–post-test design. Using nonprob-

ability purposive sampling, study participantsincluded anesthesiologists, nurse anesthetists,

preoperative registered nurses, intraoperative

registered nurses, postoperative registered nurses,

and registered nursesworking in the intensive care

unit at a 635-bed tertiary care hospital. Periopera-

tive and intensive care registered nurses were

included because oftentimes anesthesia providers

need their help in applying cricoid pressure during

induction of anesthesia, emergency intubation, or

during bag-mask ventilation. Exclusion criteriaincluded participants unable to speak English.

Sample size was limited to consenting participants

actively working at the hospital during the study

dates.

The institutional review board of an affiliated uni-

versity approved the study protocol and required

the inclusion of a human subjects consent form.Study approval was also obtained from the hospi-

tal’s institutional review board. Permissions were

also obtained from the hospital’s chief nursing offi-

cer, nursing unit directors, and nurse anesthesia

administrators.

Instrument

The use of a plastic laryngotracheal model placed

upon an infant scale with a digital display was uti-

lized for data collection (Figure 1). A towel covered

the digital display during the intervention to pre-

vent the participant from viewing their forceapplied to the model before and after the test. The

model was a life-sized upper airway with clearly

defined airway anatomy including cricoid cartilage.

An electronic baby scale, EBSA-20, infant scale with

a digital display of 0 to 20 kg, with 0.01 kg incre-

ments, was used.

This instrument has been used and validated byother researchers. Herman, et al.20(p862) described

it as ‘‘an effective and easy model for instructing,

practicing, and refreshing the recommended force

240 LEFAVE, HARRELL, AND WRIGHT

to apply andachieveesophageal occlusionusing the

Sellick maneuver’’ allowing ‘‘one to better obtain a

morequantifiable and reproduciblemeansof assess-

ing effort.’’ Beavers et al9 used this toolwith success.

May and Trethewy21(p208) used a less descriptivelaryngeal model mounted on a self-calibrating digi-

tal postage scale stating, ‘‘the use of such devices

for this purpose has been validated.’’

Methods

Participants were presented an informed consent

to participate in the study. If needed, explanation

Figure 2. Data collection

was provided by the investigator, and questions

were answered. A string of alphanumeric identi-

fiers were used to maintain participant anonymity.

After verbal consent was obtained, the partici-

pants were asked to complete an initial demo-graphic data form delivered via electronic survey

(Figure 2). This instrument was used to collect

baseline demographics including gender, hand

dominance, occupation, years of application of

cricoid pressure, cricoid pressure training within

the previous 12 months, and knowledge of the

amount of cricoid force required during cricoid

pressure.

form. ID, identification.

CRICOID PRESSURE FORCE AND TECHNIQUE 241

The participant was then asked to apply pressure

to the laryngotracheal model pretest with the dig-

ital display covered by the towel. The investigator

assessed and documented the anatomic applica-

tion, technique, hand used, and force applied tothe model. Force was measured by instructing

the participant to alert the investigator when

they applied adequate force to the model. Next,

an educational intervention in the form of a 2-min-

ute video via laptop was given to the participants,

allowing two times to practice cricoid pressure on

the laryngotracheal model during the intervention

while viewing the digital display of force on thescale. The video was published by the researcher,

Figure 3. Postintervention educational handout. This fi

describing the indications, anatomy, technique,

force, and contraindications of cricoid pressure.

After the intervention, participants were asked to

reapply cricoid pressure on the laryngotrachealmodel with the digital display of force covered.

Again, the investigator assessed and documented

the anatomic application, technique, hand used,

and force applied to the model. On completion

of the study, participants were notified of their pre-

test and post-test results and provided an educa-

tional handout (Figure 3) describing the

significance, indications, and technique of cricoidpressure.

gure is available in color online at www.jopan.org.

242 LEFAVE, HARRELL, AND WRIGHT

Statistical Analysis

Descriptive statistics were calculated for the three

continuous variables of force pretest, force post-test, and years of cricoid pressure application.

Descriptive statistics for discrete variables

including yes and no questions were reviewed.

Wilcoxon signed rank test determined if there

were significant differences between the identifi-

cation of cricoid anatomy pretest and post-test.

A Kruskal-Wallis test was used to determine if pre-

test and post-test differences were significantlydifferent among the various participant occupa-

tions. Pearson correlation analysis determined if

the pretest and post-test forces were related to

the participant’s years of cricoid pressure applica-

tion. Nominal by interval cross tabulation of

continuous data (pretest and post-test force) and

discrete data (nominal yes or no data) determined

whether pretest and post-test forces were depen-dent on gender or hand dominance.

Findings

A total of 61 participants were involved in thisstudy including two anesthesiologists, 17 nurse

anesthetists, 7 preoperative registered nurses, 15

intraoperative registered nurses, 10 postoperative

registered nurses, and 10 intensive care nurses

(Figure 4). The recommended cricoid pressure

was 3 to 4 kg (30 to 40 N). Descriptive analysis

revealed a mean pretest force of 2.47 kg, mean

post-test force of 3.78 kg, and amean of 10.66 yearsof experience applying cricoid pressure. Seventy-

Figure 4. Participant demographic distribution according

able in color online at www.jopan.org.

seven percent of participants were female and

23% male. Hand dominance analysis revealed

88.5% of participants were right handed, and

11.5% were left handed. Only 14 of the 61 partici-

pants gave responses for the data collectionquestion regarding their pre-existing knowledge

of the recommended force of cricoid pressure.

Of the 14, only 2 participants answered correctly

within the range of 3 to 4 kg (30 to 40 N).

Twelve participants (19.7%) identified correct

cricoid cartilage pretest, whereas all participants

correctly identified the anatomy post-test. TheWilcoxon signed rank test revealed that there

was a significant difference (Z 5 27.000,

P 5 .000) between the participants’ identification

of correct cricoid cartilage post-test versus pre-

test (Figure 5).

The Kruskal-Wallis test determined that there was

a significant difference (P 5 .010) between theoccupation of the participant and the force

applied before the test. None of the anesthesiolo-

gists, 10 nurse anesthetists, 1 preoperative nurse,

2 intraoperative nurses, 2 postoperative nurses,

and 1 intensive care nurse applied correct cricoid

pressure force pretest. However, there was no sig-

nificant difference (P5 .111) between the occupa-

tion of the participant and the force applied afterthe test. One anesthesiologist, 11 nurse anesthe-

tists, 4 preoperative nurses, 11 intraoperative

nurses, 6 postoperative nurses, and 9 intensive

care nurses applied correct cricoid pressure force

post-test (Figure 6). Pearson correlation analysis

to occupation. RN, registered nurse. This figure is avail-

Figure 5. Correct identification of cricoid anatomy

in percentage by participants. Preop, preoperative;

RN, registered nurse; Intraop, intraoperative; Postop,

postoperative; ICU, intensive care unit. This figure is

available in color online at www.jopan.org.

CRICOID PRESSURE FORCE AND TECHNIQUE 243

determined that the pretest (r 5 0.214, P 5 .098)

and post-test (r 5 20.074, P 5 .573) forces were

not related to the participant’s years of cricoid

pressure application.

Nominal by interval cross tabulation determined

pretest (Eta 5 .142) and post-test (Eta 5 0.026)forces were not dependent on gender. Likewise,

nominal by interval cross tabulation determined

pretest (Eta 5 0.080) and post-test (Eta 5 0.058)

forces were not dependent on hand dominance.

Conclusions

The clinical importance of cricoid pressure in the

prevention of regurgitation and aspiration of

Figure 6. Mean force applied in kilograms pretest

and post-test by participants. Three kilogram to 4 kg

is the correct amount of cricoid pressure required.

Preop, preoperative; RN, registered nurse; Intraop,

intraoperative; Postop, postoperative; ICU, intensive

care unit. This figure is available in color online at

www.jopan.org.

gastric contents has been established throughout

history. It is prudent to ensure that the medical

community practices the techniquewith accuracy.

This study revealed that participants lacked prior

knowledge of correct cricoid anatomy and pres-sure as well as the ability to apply correct force

to the laryngotracheal model before an educa-

tional intervention. The intervention used in this

study proved successful in educating medical pro-

viders. A greater percentage of participants were

able to successfully apply 3 kg to 4 kg of force to

the model post-test, and 100% of participants iden-

tified correct cricoid anatomy post-test.Sellick1(p405) said ‘‘the nurse or midwife accompa-

nying the patient can be shown in a few seconds

how to do it [apply cricoid pressure].’’ This was

accomplished in this study within 2 minutes using

the educational video.

Specifically, it is important to note that as one

intraoperative registered nurse applied force tothe model, no force was detected on the digital

display by the investigator. On checking with

the nurse if she was applying pressure, she

stated that she was indeed applying pressure.

She further stated that she always squeezes the

throat and would never push down because

that would obstruct the view of the person intu-

bating. This nurse had been applying cricoidpressure incorrectly for 38 years. Fortunately,

she applied a post-test pressure of 2.98 kg.

This single participant’s experience alone ver-

ifies the significance of education and training

of cricoid pressure.

Acknowledgments

The authors thank Linn M. Stranak, DA, at Union University for

his statistical help and expertise.

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