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ntensive and Critical Care Nursing (2008) 24, 359—365

RIGINAL ARTICLE

inimal occlusive volume cuff inflation: A surveyf current practice

ouise Rosea,∗, Leanne Redlb,1

Lawrence S. Bloomberg Faculty of Nursing, University of Toronto, 155 College Street,oom 276, Toronto, ON M5T1P8, Canada

Intensive Care Unit, The Royal Melbourne Hospital, Grattan Street,arkville, Melbourne, VIC 305

Accepted 14 May 2008

KEYWORDSEndotracheal intubation;Mechanical ventilation;Ventilator associatedpneumonia;Cuff inflation;Minimal occlusivevolume

∗ Corresponding author. Tel.: +1 416ax: +1 416 978 0665.

E-mail addresses: louise.rose@utoeanne.redl@mh.org.au (L. Redl).

1 Tel.: +61 3 9342 7209; fax: +61 3 9

964-3397/$ — see front matter. Crowoi:10.1016/j.iccn.2008.05.002

0, Australia

SummaryObjective: To describe the minimal occlusive volume (MOV) procedure used to mon-itor cuff inflation and identify practice variation.Research methodology: Self-administered questionnaire.Setting: Adult intensive care unit in an Australian university-affiliated hospital.Results: Survey response was 71% (80/113). Three methods of MOV were identified.Full cuff deflation, followed by reinflation, removal of 1 mL increments of air untila leak was detected, then restoration of cuff seal with 1 mL of air was the pre-ferred method (47/80 respondents, 59%) (Method 1). Full cuff deflation followed byincremental addition of air until the MOV was established was used by 25/80 (31%)respondents (Method 2). Two (2.5%) nurses established MOV without full cuff defla-tion (Method 3), five (6.25%) used more than one method and one (1.25%) nurse didnot perform cuff checks. Practice variation was identified for patient positioning,confirmation of cuff seal, and cuff leak management. Consistency of practice wasnoted in MOV procedure frequency, the number of nurses required, pre-oxygenationand oropharyngeal suctioning prior to cuff deflation.

Conclusion: Substantial practice variation for certain aspects of cuff managementwas noted. Evidence to support the efficacy of MOV procedural elements is requiredto limit practice variation and reduce risk to patients.Crown Copyright © 2008 Pu

978 3492;

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342 8812.

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blished by Elsevier Ltd. All rights reserved.

ntroduction

ndotracheal intubation is a life-saving procedurehat enables the application of mechanical ven-ilation. In adults, endotracheal tubes have aalloon-like cuff that when inflated seals the airway

y Elsevier Ltd. All rights reserved.

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enabling delivery of positive pressure ventilationwithout loss of tidal volume or aspiration of pha-ryngeal contents (Pierce, 2007). Over the last fourdecades, cuff design has evolved from a rigid rub-ber structure that rapidly caused tracheal epithelialdamage (Ganner, 2001) to high volume—low pres-sure cuffs that conform to tracheal contours atlow pressures resulting in less ischaemic damage(Guyton, 1990). More recently, third generationpolyurethane membrane cuffs have been developedthat enable better prevention of aspiration whilemaintaining low cuff pressure (Crimlisk et al., 1996;Sengupta et al., 2004).

To prevent complications associated with under-inflation (aspiration of pharyngeal contents and riskof ventilator associated pneumonia [VAP]) or over-inflation (tracheal ischaemic damage), the cuff ismonitored intermittently. Minimal occlusive volume(MOV) is one of the four methods used to monitorcuff inflation. This method involves the additionof sufficient air to abolish an air leak on inspira-tion determined by auscultation over the trachea(Pierce, 2007). Other methods include the minimalleak technique that allows a small cuff leak on inspi-ration, cuff pressure manometry, and pilot balloonpalpation.

In the literature there is little consensus onthe best method for monitoring ongoing cuff infla-tion, the frequency, or most appropriate patientposition for monitoring to be performed (Crimlisket al., 1996; Ganner, 2001; Sole et al., 2003).Certain aspects of the MOV technique also lack evi-dence or clear rationales. This lack of consensusmay result in practice variation and uncertaintyin clinical practice. Improper and inconsistentcuff management practices may increase the riskfor complications associated with inappropriatecuff inflation including VAP and ischaemic dam-age to the trachea. The aim of the currentstudy was to describe the application of the MOVprocedure and identify practice variation in anintensive care unit (ICU) that uses MOV as thesole method of cuff inflation and ongoing monitor-ing.

Methods

Participants and setting

This survey was conducted at the ICU of The Royal

Melbourne Hospital, Victoria, Australia. This ICU isa 24-bed adult, combined medical—surgical unit ina university-affiliated teaching hospital. Approxi-mately, 100 patients per month receive treatmentwith mechanical ventilation in this ICU. All nursing

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taff employed in the ICU were eligible to partici-ate.

thical considerations

pproval for this survey was obtained from the Insti-utional Review Boards of Melbourne Health andMIT University. The return of a completed ques-ionnaire was considered indicative of consent.

nstrument

o inform the study and generate questionnairetems, we conducted a detailed search of Med-ine, Proquest, PubMed, and CINAHL using theerms endotracheal cuff, cuff pressure, trachealube, airway management and ventilator asso-iated pneumonia searched individually and inombination. Additionally, nursing clinicians withxpertise in cuff management were consulted todentify procedures relevant to the MOV technique.

process of item reduction designed to minimiseedundancy and completion time and maximiseesponse rate resulted in a two-page questionnaire.his questionnaire was then tested for clinical sen-ibility to detect inappropriate, redundant itemsr important omissions and determine the claritynd face validity by a team of senior medical andursing staff.

The questionnaire sought information on nurseemographics, technical aspects of the MOV tech-ique, the frequency of ongoing cuff monitoring,anagement of a cuff leak, and cuff managementrocedures prior to extubation. Questions relatingo the participant’s conduct of the MOV techniqueere formatted using a three-item ordinal scale

always, sometimes, never). Participants were alsosked to comment on perceived advantages and dis-dvantages of the MOV technique.

ata collection

he survey was distributed to staff on each nursinghift over 2 weeks. Surveys were hand deliveredo staff members by senior nursing clinicians notirectly involved in the study. This method of sur-ey distribution was selected as nurses were knowno check hospital mail (both paper and electronic)nfrequently. All surveys were returned to a sealedox located in the ICU to maintain the confidential-ty of responses.

ata analysis

ategorical data (including demographic and proce-ural information) were expressed as proportions.

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or analytical purposes, participants were cate-orised as senior clinicians (those with more thanve years ICU experience) and junior cliniciansthose with less than five years ICU experience).esponses for cuff check procedures by these tworoups were then compared using chi square orisher’s exact tests as appropriate. A p-value of0.05 was considered statistically significant and allests were two-tailed. All analyses were performedsing Minitab 14 (Minitab, 2003).

Comments on the perceived advantages andisadvantages of the MOV technique were anal-sed using content analysis to identify themesBurns and Grove, 2001). The data were coded ini-ially for key phrases such as ‘minimise trachealamage’ or ‘increased risk of aspiration and ven-ilator associated pneumonia’ and then examinedor repetition, characteristics and dimensions thatdentified and confirmed categories. Two review-rs coded the data independently. Discrepanciesn coding were discussed until a consensus waseached. Percentages were then calculated for theumber of responses to each identified theme.

esults

emographics

f the 113 surveys distributed, 80 were returnedresponse rate 71%). Table 1 shows the demographic

Table 1 Status and experience of nurse respondents(N = 80)

Characteristic n (%)

Position heldSenior management (associate

nurse manager, nurse educator)9 (11)

Clinical nurse specialist 30 (37.5)Critical care nursea 27 (33.5)Student critical care nurse 7 (9)Registered nurse 7 (9)

Years of ICU experience≤2 years 8 (10)>2 years to ≤5 years 22 (27.5)>5 years to ≤10 years 27 (33.5)>10 years 23 (29)

Years of employment in participating ICU≤2 years 11 (14)>2 years to ≤5 years 44 (55)>5 years to ≤10 years 12 (15)>10 years 13 (16)a RN with postgraduate level critical care specialty quali-

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haracteristics of the nursing respondents. Fiftyercent of the nurses surveyed had greater thanve years experience in the ICU specialty.

uff check procedure

articipants were given three options to bestescribe the method they used to ascertain MOV.he majority of respondents (47/80, 59%) alwaysetermined MOV by full cuff deflation to establishhe volume of air in the cuff, followed by rein-ation with the volume of air removed. Air washen removed in 1 mL increments until a leak wasetected. The MOV was then restored with theddition of 1 mL of air (Method 1). An alternativeethod (Method 2), used by 25 (31%) of respondentsas full deflation of the cuff to establish the vol-me of air followed by incremental addition of airntil the MOV was established. Two (2.5%) respon-ents established MOV by incremental removal ofir without performing full cuff deflation (Method). Five (6.5%) respondents reported they used aariety of methods, and one respondent did not per-orm cuff checks. More junior nurses stated theylways used Method 1 compared to experiencedurses (p = 0.004). Choice of MOV method was notssociated with prior employment in another ICUp = 0.4).

requency of procedure

f the 79 respondents who performed cuff checks,9/80 (87%) performed a MOV procedure once perursing shift (both 8 and 12 h shifts are availablen this ICU). No nurses reported conducting morerequent cuff checks. Six (8%) nurses reported cuffhecks were performed once per 24 h and four (5%)urses only checked the cuff based on an assesseduff leak.

atient positioning

he MOV technique was performed in the semi-ecumbent position (defined as 30—45◦ head of bedlevation) by 36/79 (46%) respondents, though aumber of other patient positions were consideredcceptable (Fig. 1).

ssociated procedures

ll 79 respondents suctioned the oropharynx prior

o cuff deflation. Other aspects of the procedure,erformed by the majority of respondents, includedse of two nurses to perform the technique, andre-oxygenation prior to cuff deflation (Table 2).he majority of nurses did not perform aspiration

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Figure 1 Patient positioning during MOV procedure. Nochange indicates the cuff check procedure was per-

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formed without changing the patient’s position. ‘Other’was selected by three respondents though the alternativeposition was not described.

of the nasogastric tube prior to cuff deflation rou-tinely. Aspiration of the nasogastric tube prior tocuff deflation was not associated with the nurse’slevel of ICU experience (p = 0.3) or prior employ-ment in another ICU (p = 0.7). Few nurses reportedusing a manual inspiration when confirming a cuffseal during the MOV technique.

Cuff seal

To assess adequacy of cuff seal between MOVprocedures, auscultation over the trachea as thesole method (23/79, 29%), or in combination withassessment of expired tidal volume measured bythe ventilator (27/79, 34%) were used most fre-quently. Other methods included manual inspiration

via the ventilator (14/79, 18%) or palpation of thepilot balloon in combination with other methods(15/79, 19%). No respondent used balloon palpationexclusively.

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Table 2 Minimal occlusive volume technique (N = 79)

Technique Always, n (%) Someti

Suction oropharynx priorto cuff deflation

79 (100) 0 (0)

Two nurses to performprocedure

76 (96) 3 (4)

Pre-oxygenation prior tocuff deflation

74 (94) 4 (5)

Aspirate nasogastric tubeprior to cuff deflation

11 (14) 36 (46)

Manual inspiration toconfirm cuff seal

1 (1) 17 (21.5

L. Rose, L. Redl

udible cuff leak

o manage an audible cuff leak, 28/79 (35%) respon-ents continued cuff inflation to obtain a sealrrespective of the volume of air required. A fur-her 13/79 (16.5%) respondents continued cuffnflation and also notified medical staff. Twenty-hree (29%) respondents would attempt a rangef troubleshooting techniques including assessmentnd manipulation of endotracheal tube insertionength and patient position. Notification of medi-al staff was the first course of action for 12/7915%) respondents. Two (2.5%) nurses assessed cuffressure using a manometer. Only one respondentccepted an ongoing cuff leak.

Participants were asked to identify the maximumolume of air acceptable for MOV. The most fre-uent response was 12 mL (34/79, 43%). Fifteenilliliter was the maximum volume accepted by

2/79 (28%) nurses, 10 mL by 15/79 (19%) nurses and0 mL by 3/79 (4%) nurses. A further five respon-ents did not answer this question.

xtubation

rior to extubation, 57/79 (72%) participants rou-inely checked cuff volume to assess airwayedema. This procedure was not restricted toenior nurses (p = 0.9) or to those nurses whose ICUxperience was limited to the participating institu-ion (p = 0.6). Detection of a reduced cuff volumeas considered an appropriate reason to defer theecision to extubate by 50/79 (63%) respondents.

dvantages and disadvantages

f the 79 respondents, 73 made comment on the

erceived advantages and disadvantages of regularuff monitoring using MOV. Five advantages weredentified: to minimise damage to the tracheal wall56% of respondents), to detect airway oedema

mes, n (%) Never, n (%) Did not answer, n (%)

0 (0) 0 (0)

0 (0) 0 (0)

1 (1) 0 (0)

31 (39) 1 (1)

) 59 (75) 2 (2.5)

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49%), to provide an adequate seal to prevent aspi-ation (15%), to facilitate pressure area care for therachea (13%) and to enable delivery of mechanicalentilation (4%).

Perceived disadvantages of the MOV procedurencluded: increased risk of aspiration and VAP dueo full cuff deflation during the procedure (93%f respondents), loss of positive end expiratoryressure (PEEP) and interference with mechanicalentilation (21%), increased risk of tube migrationr extubation (12%), patient discomfort (12%) andnaccuracy of the technique (5%). The MOV proce-ure was considered resource intensive comparedo cuff pressure manometry by 15% of respondents.

iscussion

o our knowledge, this survey is the first to providen in-depth description of the MOV procedure andssociated clinical processes in an ICU setting. Theesults of this survey indicate considerable practiceariation. Substantial differences were noted in theethod used to achieve MOV, patient positioninguring the procedure, the most appropriate methodor confirming cuff seal, and management of auff leak. Practice differences were only partiallyxplained by the level of ICU experience. Juniorursing staff were more likely to use Method 1, aechnique which theoretically decreases the risk ofspiration as the cuff is deflated for a shorter time.his method is advocated by the unit’s nurse edu-ators whose role is to provide clinical educationo junior staff members completing a postgraduateiploma in the critical care specialty. Other prac-ice variation was not associated with nurse senior-ty or exposure to other ICU clinical environments.

Little evidence is available that identifies theost appropriate method for ongoing monitoring

f cuff inflation. Moreover detailed description ofethods, associated processes, and evidence of

fficacy are lacking. Step-by-step description ofow to ascertain MOV in a cuff that is alreadynflated is required. Mechanical ventilation andritical care texts primarily describe the MOV tech-ique for initial cuff inflation with cuff pressureonitoring (CPM) recommended for ongoing cuffonitoring (AACN, 2005; Pilbeam and Cairo, 2006;

ierce, 2007). However, practice surveys conductedn the United Kingdom suggest CPM is used infre-uently (Spittle and Beavis, 2001; Vyas et al., 2002).

urrently, there are no studies that confirm theuperiority of CPM over the MOV technique for ongo-ng monitoring of cuff inflation.

Disadvantages associated with the MOV tech-ique include interruption of positive pressure

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entilation resulting in loss of PEEP and hypox-emia, risk of aspiration and hyperinflation onuff reinflation, and damage to the pilot valvehrough repetitive use (St John, 1999). Disadvan-ages of CPM include a sensitivity to changes inead, patient and tube position, coughing, lungompliance, airway and intrathoracic pressuresCrimlisk et al., 1996; Vyas et al., 2002; Pierce,007). Pressure readings taken prior to a positionhange or altered lung compliance may not accu-ately reflect cuff pressure. Additionally, patientsith high intrathoracic or airway pressures require

ncreased cuff pressure to maintain an adequateeal and may be at increased risk of ischemic injury.lternatively, maintenance of pressure within theecommended range will predispose these patientso aspiration (Bouvier, 1981; Guyton et al., 1997).

In this survey, the maximum frequency ofonitoring cuff inflation was once per shift.his practice is congruent with recommendations

n mechanical ventilation texts (MacIntyre andranson, 2001; AACN, 2005; Pilbeam and Cairo,006) and practice survey reports (Sole et al., 2002,003; Rose and Redl, in press). Failure to monitoruff inflation at least once per nursing shift maylace the patient at increased risk of aspiration andubsequent ventilator associated pneumonia dueo underinflation or tracheal mucosal damage inhe presence of overinflation. Patients at increasedisk of complications associated with cuff inflationnclude those with airway oedema, variable lungompliance and airway pressures (Guyton et al.,997), and hypotension due to low perfusion pres-ure in the trachea (Pilbeam and Cairo, 2006).

Cuff monitoring procedures should be performedn the semi-recumbent position to reduce stimula-ion of the gag reflex and risk of aspiration (AACN,005; Metheny et al., 2006). Though the major-ty of respondents in the current survey used thisosition, some practice variation was noted.

During cuff monitoring procedures, the ability ofhe cuff to seal the airway is decreased while aspi-ation risk is increased due to stimulation of gagnd cough reflexes associated with oropharyngealnd tracheal suctioning. Large residual volumesithin the gut further increase the risk of aspiration

Metheny et al., 2006). Aspiration of nasogastricontents prior to cuff deflation is another interven-ion that may reduce the risk of aspiration of gastricontents. Surprisingly this procedure was routinelyerformed by only 14% of the survey respondents.

During the inspiratory phase of a positive pres-ure breath the airways expand resulting in a drop inressure (St John, 1999). To ensure appropriate cuffnflation, the cuff seal should be assessed duringnspiration using a positive pressure breath prefer-

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ably via the ventilator using either a sigh breathor manual inspiration function (AACN, 2005). In thecurrent survey few respondents used this techniqueto confirm cuff seal during the MOV procedure, or toascertain cuff seal between cuff checks. Similarly,few ICUs identified this practice in a recent surveyof cuff management in Australia and New Zealand(Rose and Redl, in press).

Loss of cuff volume and/or pressure is a commonoccurrence that increases the risk of aspiration ofpharyngeal contents and VAP (Rello et al., 1996;Valencia et al., 2007). Notably, there is an absenceof information in the literature to guide manage-ment of an audible cuff leak once the recommendedvolume or pressure has been reached. In the cur-rent study, the majority of nurses stated they wouldcontinue cuff inflation to obtain a seal irrespec-tive of the volume of air required indicating greaterconcern for the risk of aspiration than trachealdamage. Nurses cited maximal acceptable cuffinflation volumes ranging from 10 to 20 mL. Man-ufacturers of modern high volume, low-pressurecuffs do not provide guidelines as to the recom-mended maximum cuff volume.

Severe consequences of cuff overinflationincluding tracheal rupture, tracheo-carotid arteryerosion and tracheal innominate artery fistulasare now rare due to widespread use of thesecuffs (Sengupta et al., 2004). Nurses, however,need to remain mindful of the consequences ofoverinflation when large volumes of air are used.Conversely, VAP remains an important cause ofmorbidity and mortality in the critically ill (ATS,2005). Respondents also perceived full cuff defla-tion during the MOV procedure increased the risk ofaspiration and VAP. Currently there are no studiesto demonstrate an increased risk of aspiration withMOV compared to other methods of cuff monitoringsuch as cuff pressure manometry or the minimalleak technique.

Limitations

This survey has limitations. First, despite a reason-able response rate, the results may not representthe practice of non-responding nurses. Second,survey findings are the result of a self-report ques-tionnaire and as such may reflect nurses’ best orintended practice rather than clinical reality. Third,this survey represents practice of a single ICU inwhich MOV was the sole method of cuff inflation and

ongoing monitoring. As such, the described prac-tice may not be generalised to other ICU settings. Arecent survey of cuff inflation practices in Australiaand New Zealand (Rose and Redl, in press) foundMOV was used either in combination with cuff pres-

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ure manometry, or as the sole method of ongoinguff monitoring, in 50% of ICUs surveyed indicatingidespread use of this technique.

onclusion

ithin the literature, evidence to support variousspects of the MOV procedure is limited. The resultsf our survey suggest, within this single ICU setting,ubstantial practice variation for certain aspectsf cuff management exists. Despite concern forhe risk of aspiration associated with cuff defla-ion during the MOV technique, procedures suchs semi-recumbent positioning, aspiration of gas-ric contents prior to cuff deflation and manualnspiration to confirm cuff seal were not uniformlymployed. As a result of the findings of this survey,nit guidelines for ongoing cuff monitoring haveeen revised to standardise practice. Additionally,study has been initiated that examines the rate

f gross aspiration using blue dye inserted into theral cavity prior to cuff monitoring with both theOV and cuff pressure monitoring techniques.

ole of funding source

his study was supported by a research grant fromMIT University.

onflict of interest

one declared.

cknowledgement

he authors would like to thank the staff of thentensive care unit of The Royal Melbourne Hospital.

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