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Key points

• Interface selection is mainly influenced by the patient’s face shape, mouth/nose breathing pattern, nasal pathology, experience of the staff, patient choice and equipment availability. Interfaces covering the mouth and nose are usually the first choice for acute NIV.

• Compatibility of the chosen interface with the ventilator circuitry should be checked and the exhalation port identified before NIV is started.

• Large air leaks affect the efficacy of NIV and should be avoided, whereas small air leaks can be compensated for by ventilators designed for NIV and are usually tolerated if they do not irritate the patient or disturb sleep.

• Routine assessment of the skin and risk of pressure ulcers, regular pressure relief and skin-protective strategies should be included in the routine application of NIV to reduce discomfort and the occurrence of soft tissue damage.

How to avoid interfaceproblems in acute noninvasiveventilation

SummaryNoninvasive ventilation (NIV) applied via different interfaces is increasingly usedin the treatment of acute respiratory failure. One of the key factors determiningthe success of NIV is the choice of interface. Interface selection, fitting andhandling can be challenging as NIV application can be complicated bydiscomfort, air leaks, skin damage or conjunctivitis. The aim of this article isto provide practical information on interface choice, technical aspects of maskfitting and prevention of mask-related problems during the acute delivery of NIV.

Educational aimsN To help the reader to recognise the different features of interfaces and to discuss

common interface-related problems

N To provide practical recommendations to facilitate the choice and application ofinterfaces in order to reduce complications

The use of noninvasive ventilation (NIV) hasgrown continuously over the past two dec-ades. It has become a standard of care in thetreatment of many forms of acute respiratoryfailure (ARF) and is now frequently applied inintensive care units (ICUs), emergencydepartments, post-surgical recovery rooms,step-down units and respiratory wards [1–4].

Despite the overall success of the treatmentmodality, NIV failure rates still range between18% and 40% in the acute setting [1, 3, 5–7].Primary failure of NIV reflects failure ofuptake of the technique and control ofrespiratory failure; secondary failure is seenwhen respiratory failure progresses despiteoptimal NIV use.

HERMES syllabus link:module E.1.6

Statement of InterestNone declared.

ERS 2014

N

N

Breathe | September 2014 | Volume 10 | No 3 231DOI: 10.1183/20734735.003414

Anne-Kathrin Brill Dept of Sleep andVentilation, Royal Bromptonand Harefield NHSFoundation Trust, London,UK

Dept of Sleep andVentilation, Royal Bromptonand Harefield NHSFoundation Trust, SydneyStreet, London, SW3 6NP,UK

[email protected]

Patient selection, underlying pathology,the severity of ARF, expertise with NIV andinterface tolerance all have a major impact onthe success or failure of NIV. Interface-relatedproblems such as air leaks, skin lesions ordiscomfort are still common reasons for pooradaptation to NIV and NIV failure [8–10].They can often be addressed successfully withbasic knowledge of the principles of maskfitting and handling.

The purpose of this article is to provide anoverview of strategies to anticipate, prevent andmanage interface-related problems in acute NIV.

Interface selection

A greater variety of different interface types,styles and materials have been developed bydevice manufacturers in recent years. Thisallows a suitable interface to be found fornearly every patient in most situations, buthaving to deal with many different interfacesand be able to select the most appropriateone can be challenging for clinical staff. Thereare six main classes of interfaces that arecommercially available in various sizes, all ofwhich have their advantages and disadvan-tages (table 1). Custom made masks are

another option, but in the acute setting withcritically ill patients, there is usually notenough time to fabricate these.

Interface selection is mainly influenced bythe patient’s individual characteristics (i.e.facial anatomy, breathing pattern and indi-vidual level of comfort) and clinical effective-ness, but the experience of the staff,equipment availability and economic aspectsare also relevant. In the few studies compar-ing different types of interfaces in acute NIV,the improvements in respiratory parameters,i.e. dyspnoea, respiratory rate and arterialblood gases, were usually similar and there isno strong scientific evidence that one type ofmask is necessarily or consistently better thanothers in terms of clinical efficiency. However,patients in ARF often mouth-breathe and,even if they can be started on a nasal mask, aswitch to an alternative interface covering thenose and mouth is necessary in manypatients if mouth air leaks occur [11, 12]. Inclinical practice the most common initialinterface to treat ARF with NIV is, therefore,an oronasal mask. This was reflected in theresults of a large web-based survey in Europeand North America, with oronasal masks(70%) being the first choice followed by totalface masks, nasal masks and helmets [13].

Oronasalmask

Total facemask

Nasalmask

Nasalprongs

Mouthpieces

Helmet

Acute setting

Use outside HDU/ICU

High level of noise

High gas flow required

Chance of eye irritation

Speaking is easier

Less claustrophobic

More likely to have leaksin the acute setting

Coughing andexpectoration is easier

Useful for prominentfacial anatomy

No pressure on the nasal bridge

Nasal patency required

Figure 1Different interface types. HDU: high dependency unit. Closed circles: applicable to the interface; open circles: analternative, but less common or less frequent option.

Table 1

Interface problems in acute noninvasive ventilation

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The ability to try different mask types andsizes quickly may enhance tolerance aspatients who do not adapt well to one typeof mask may comply with another. Having anumber of different mask types and sizesattached to the NIV ventilator can, therefore,be advantageous, although financial con-straints may limit those available. Mostmasks come with fitting gauges to avoidselection of a mask that is too large or toosmall and clinicians are encouraged to usethem to reduce complications. The maskshould not encroach on the corners of theeyes or lips. Changing the interface canreduce NIV failure, and is always worth tryingif large leaks are seen and demonstrated onventilator software or the type of interface isnot well tolerated by the patient, but experi-menting with interfaces should not delayintubation in a severely ill patient if NIV isclearly failing. When switching to a differentmask, trigger sensitivity, pressurisation level,and compatibility with the circuitry must bechecked.

In the long-term setting, nasal masks arerated to be more comfortable than othermask types [14] and cause skin problems lessoften. If the patient is stable and there are nomajor mouth air leaks, it may be reasonableto swap to a nasal mask or nasal prongs. Inaddition, patients in the post-acute settingcan sometimes be encouraged to continueNIV by switching to a less claustrophobicinterface type.

Carbon dioxide rebreathing:dead space and ventilatorcircuits

Depending on the ventilator and circuit used,NIV can be applied either via an open single-limb circuit or a closed double-limb circuit.An open single-limb circuit requires a ventedmask with a built-in exhalation port or anonvented mask and an additional exhalationvalve in the circuit to allow carbon dioxide(CO2) removal. A closed double-limb circuitis used with a nonvented mask and has anexhalation port or filter for CO2 removalwithin the system. It is essential to be awareof which circuit is used when the mask ischosen. The wrong combination, for examplea nonvented mask in an open single-limbsystem and no exhalation port in the system,

can be fatal. Also, an exhalation port shouldnever be obstructed intentionally (e.g. tapingup the holes in the mask) to reduce leakage.Different colours on the mask or the maskelbow, with a blue colour representing non-vented masks and a clear entrainment elbowfor vented models (fig. 1), can give guidance,but it is not always a guarantee. For safetreatment, it is important to locate theexhalation port, assure its patency and checkcompatibility of the circuit and interface priorto the start of NIV.

The interface itself adds an additionaldead space to the system, which can increaseCO2 rebreathing. Bench studies have sug-gested that CO2 rebreathing increases withinterfaces that have a higher internal volumeand decreases with a built-in exhalation port[15]. The in vivo effect is only small and, withthe exception of the helmet, facial masks areusually interchangeable [16].

Initiation of NIV

The first few hours of acute NIV are extremelyimportant, and time spent fitting the maskand building the patient’s confidence is wellinvested. Having a mask strapped immedi-ately over the face can be very frightening fora breathless patient in ARF, particularly if theperson is naıve to NIV. A careful explanationof what will happen and why NIV is used aswell as a description of the sensation the

Figure 1A vented mask with a clear elbow, grey adapter and integrated exhalation port on theleft for single limb circuits. A nonvented mask with a blue elbow for dual limb systems isshown on the right. Masks manufactured by ResMed Ltd. (Abingdon, UK).


Breathe | September 2014 | Volume 10 | No 3 233

patient is likely to experience can help tofacilitate the treatment. Initiating NIV withlower pressures while holding the mask orhaving the patient hold the mask in place andnot attaching the straps until the patient isready to tolerate it can also help the patient toacclimatise. Once the patient is able totolerate the mask, it can be secured with thehead straps.

Prevention andmanagement of mask-related side-effects

At this point, the clinician who fits the maskhas to achieve a good mask seal whileproviding the maximal possible comfort andpreventing mask-related complications.Initially reducing air leaks is the major goalof the mask fitting, but the longer thetreatment lasts, the more likely it is thatcomplications, including facial skin erythema,skin breakdown, rash, conjunctivitis or dry-ness of the mucosa, occur.

Air leaks

Intentional air leaks are incorporated into thedesign of most NIV circuits and are necessaryfor CO2 removal, but unintentional leaksaround the edge of the interface or throughthe mouth can cause problems. Large airleaks interfere with the effectiveness of thetreatment, while small air leaks can irritatethe patient, cause conjunctivitis or createnoise.

To provide adequate ventilation duringtreatment with NIV, it is important tomaintain the pressure gradient from theventilator through the tubing, and from themask to the patient’s pharynx and sub-sequent airways. Large air leaks can cause asignificant drop in the delivered intra-alveolarpressure, reduce tidal volume and lead topatient–ventilator asynchrony by affectingtrigger functions. All this contributes toineffective treatment, which is associatedwith NIV failure [17]. Therefore, large air leakshave to be minimised during NIV. Ventilatorsdesigned for NIV can compensate for smallerair leaks to a variable extent [18] and a smallamount of air leakage can be accepted aslong as the leak does not disturb the patient.

Besides using an appropriate interfacetype, with the correct size and headgear, thereare several other interventions to reduce airleaks. The most obvious, but least comfort-able, solution seems to be further tighteningof the head straps. Sometimes, loosening thehead straps or temporarily lifting the maskfrom the face and replacing it can have anequivalent or better effect without causingmore pressure on the patient’s face. Forexample, masks that incorporate doublespring air-filled cushions will fit and sealbetter if the cushions are filled with air andnot tightly pressed against the face. Differenttypes of mask cushions, for example hydrogelor foam cushions, are also available andchanging the cushion can sometimesimprove mask fit. In addition, mask supportrings, thin silicone or cotton comfort flaps,mask liners, hydrogen or foam seals can betried. If the patient’s chin keeps dropping,masks with a special under-chin support are auseful alternative option.

With the use of nasal masks or nasalprongs, air leaks through the mouth canbecome problematic. Although the use ofchinstraps or mouth taping have beensuggested, changing to a mask type thatcovers mouth and nose is usually therecommended strategy in ARF. Chinstrapscan successfully reduce air leaks via themouth in selected patients in the chronicsetting [19], but they are not always toleratedand there is little evidence to support theiruse in ARF. Also, chinstraps can causediscomfort, jaw or tooth pain and their useshould not be used to prolong an ineffectivetreatment. Mouth taping has been shown todecrease air leak from the mouth in aphysiological study in the chronic setting[20], but it cannot be recommended in ARFfor obvious safety reasons.

If a disturbing air leak cannot be con-trolled by other means and a change to adifferent interface type is not possible, a smallreduction of peak inspiratory pressure orswitching from a volume-controlled to apressure-targeted mode of ventilation canbe tried. Conversely, increasing the pressurewith pressure-targeted ventilation or tidalvolume with volume-targeted ventilation canimprove minute ventilation despite the higherleakage [21], as long as the patient toleratessuch a strategy. The additional volume willadd to the leakage, but nevertheless canincrease minute ventilation.



Eye irritation

Smaller air leaks near the eyes can causeirritation or conjunctivitis if they are notnoticed. Assessing for small air leaks byplacing the back of the hand over the area,and asking the patient about eye irritationroutinely throughout the treatment and everytime the mask is fitted, can help to preventthis complication. Artificial tears can beapplied if the eyes are affected.

Noise

If air leaks create noise, the mask should berefitted and a lining can be added to seal it.There is no problem with air leaks with thehelmet interface, but the high-flow systemcreates a higher level of noise within thedevice than other interfaces and providing earplugs for the patients can be helpful.

Mask pressure

A certain amount of pressure is usuallyneeded to keep the NIV mask in place andseal it, but an excessively tight fit isunnecessary. Too much pressure on the facecauses discomfort, contributes to skinlesions, and can endanger tolerance andsuccess of NIV.

One of the most unpleasant and painfuliatrogenic interface-related complications inNIV is facial pressure ulcers. These are seenon areas of high pressure, mainly on the nasalbridge, but can develop at any place wherethe mask or headgear has contact with theskin (fig. 2). The reported occurrence rate inARF varies depending on timing of the study,patient population, masks and skin protectivestrategies used. Reports from earlier NIVtrials range from 5% to 56% [22, 23]; althoughimprovements in mask design have helped todecrease the problem, more recent reportsstill range from 3% to 87% [24–27]. This canbe partly explained by the expansion of NIVindications towards more severely ill patientsat risk for pressure ulcers, ventilation withhigher inspiratory pressures that promote airleaks, and the constantly increasing numberof NIV services with initially less experiencedstaff and only a small selection of masksavailable. The fact that the respiratory supportneeded by the patient is naturally rated moreof a priority by medical staff than the local

skincare also contributes to the persistence ofthe problem.

Interface-related pressure ulcers aremedical-device related pressure ulcers andthe longer treatment lasts the more likely theyare to develop. A number of patient-depend-ent risk factors facilitate their occurrence(table 2), but the literature shows that themain cause for these pressure ulcers is oftenassociated with a lack of understanding ofhow and how often to remove devices andinspect the skin, and how to ensure thedevice fits appropriately to minimise frictionand pressure [28]. Most of the patient-dependent risk factors cannot be changed,but if mask fitting, regular assessment andskin protection are considered from thebeginning of therapy and adapted to theindividual patient’s needs, skin breakdowncan be avoided or at least reduced in manycases.

It is important to identify patients at riskof developing pressure ulcers from theinterface so that preventive strategies canbe initiated early. An initial assessment ofevery patient receiving NIV should includeexamination of skin integrity on the face andaround the head, in areas where the skincomes into contact with the headgear, andthe common risk factors for healthcareand device-related pressure ulcers. The skinshould be reassessed at least once pernursing shift and ideally every time the maskis removed.

The most important strategy in theprevention of pressure ulcers is to keep thepressure applied to the skin as low aspossible. Admittedly, it can be challengingto find the ideal strap tension and mask fit

b)a)

Figure 2a) Grade III pressure ulcer on the nasal bridge and b) grade II pressure ulcers on thecheeks.



that allows for both a good seal and lowpressure on the skin. A physiological study ona head model showed that a pressure of themask against the face about 2–3 cmH2Ohigher than the peak inspiratory airwaypressure is enough to prevent extensive airleaks [29]. Unfortunately, the pressure on theface cannot be measured objectively ineveryday care or in every mask type and itdoes not give information on single points ofhigh pressure, for example the nasal bridge.Therefore, the clinicians who fit the maskhave to be guided by the patient’s feedback

and their experience. The correct size of maskand headgear with a higher number ofattachment points will help to distribute thepressure more evenly around the circumfer-ence of the mask. Tightening the mask strapsuntil the air leak is only just controlled,purposely leaving a very small air leak or toallow enough space to pass at least twofingers underneath the head strap (fig. 3)[30], can also help to avoid an over-tighteningof the head straps.

Skin-protective strategies include ensur-ing the skin is clean and dry, as well as

Table 2 Risk factors for the development of interface-related pressure ulcers in NIV

General risks

Sensory impairment

Acute illness

Chronic illness

Hypoxia or very low blood pressure

Extremes of age

Low level of consciousness

Psychological status

Vascular disease

Malnutrition/dehydration

Chronic skin condition

History of previous pressure damage

Medication (e.g. analgesia, chronic steroid therapy, cytotoxins)

Extrinsic factors

Closely fitting headgear and over-tightened straps

Poorly fitted masks and headgear (i.e. too big or too small, too old or wrong style)

Mechanical forces: pressure, shear or friction from the interface

Allergy to the cushion

Other factors

Skin damage: dry, flaky, excoriated, discoloured or macerated skin

Oedema

Shape and size of nose/face

Time period that mask pressure is applied

Inability to self-manage the mask



regular pressure relief, use of special maskcushions, and application of dressings to theskin to redistribute pressure and reducefriction. For patients with very prominentanatomy or at higher risk of developingpressure ulcers, masks with softer cushions(e.g. hydrogel cushions or double spring air-filled cushions, or a combination of both) canbe used. An adjustable forehead spacer canalso help to distribute the pressure moreevenly on the face and reduce it on the bridgeof the nose. For difficult cases, the choice of amore costly, but very comfortable mask, isappropriate and can be cost-effective if itavoids intubation.

Giving the skin regular breaks frominterface pressure, ideally every 2–4 h, isimportant to reduce pressure effects andallows for inspection of the skin underneaththe mask. If this is not done, very severe skinand tissue damage can occur as demon-strated in a case report of a patient in whomthe mask was not removed for .90 consecu-tive hours [31]. Some patients deterioraterapidly when the mask is removed, but theycan be changed to an alternative interface torelieve pressure on the tissue. This conceptknown as mask rotation, i.e. a plannedsequential utilisation of different interfaces,can reduce pressure effects by alternating thepoints of highest pressure, and is also usefulto improve the tolerance and efficacy of NIV[14]. The alternation of an oronasal mask anda full-face mask allows regular pressure reliefof the nasal bridge. Other interfaces without

contact with the nasal bridge, for examplemasks with a cut-out on the nasal bridge ornasal prongs, can also be tried. In patients athigh risk of pressure ulcers, mask rotationshould be started from the beginning.

The routine use of additional protectivecoverings applied to areas with the highestpressure can reduce the occurrence ofpressure ulcers. Pads of foam [26], hydro-colloids [32] or gel distribute the pressure,reduce friction and can also reduce small airleaks at the same time (fig. 4 and 5). They arerecommended for patients with a high risk ofpressure ulcers from the beginning of NIV or,at the latest, from when the first signs ofredness appear on the skin. It is importantnot to create more pressure on the skin whenthe dressing is placed (fig. 6).

The helmet is the only interface that doesnot create pressure ulcers on the face and is auseful alternative for experienced centres, ifpressure effects on the face become a NIV-limiting problem. However, it has to be keptin mind that the use of a helmet can createskin damage along the braces under thearmpits or around the neck. A case of armvein thrombosis due to pressure from theattachment straps has been described in avery cachectic patient [33].

Upper-airway obstruction

High pressure from the lower mask strap cansometimes provoke or aggravate upper air-way obstruction by pushing the lower jawbackwards. This is normally not a problem

Figure 3The two-finger rule: when the headgear is attached itshould be possible to pass two fingers beneath it [30].

Figure 4Example for skin protection: a self-cut foam(Molnlycke Health Care, Goteborg, Sweden) dressingon a head model.



when the mask is initially fitted in an uprightor semi-recumbent position, but might beseen in some patients in the supine positionor during rapid eye movement sleep. Theobvious solution to this problem is to loosenthe straps, refit the mask or slightly increasethe expiratory positive airway pressure. Whena secure mask fit cannot be obtained withouthigher strap tension, the addition of a stiffneck collar or a rolled-up towel under the chincan be considered to help keep the upperairway open.

Skin

To reduce the risk of skin irritation it isimportant to keep the skin and mask clean

and dry throughout the treatment. If redness,rashes or blistering occur, a change to asilicone and latex free mask cushion, applica-tion of barrier cream and covering thedamaged skin to protect it when the maskis in place can all be tried. If an allergic rashoccurs, the mask cushion should be changedto a different material and application ofsteroid cream can be considered.

Regular reassessment

Movements, sweating, change of fluid statusand the tendency of Velcro straps to loosengradually over time can change mask fit.Thus, no matter how well the interface fits atthe start of NIV, it is important to routinelymonitor air leaks and skin condition and toreassess mask fit throughout the treatment.

Dryness of mucosa and humidification

Oral and nasal dryness or a blocked nose arefrequent complaints during NIV with anoccurrence rate of 10–50% [1, 2, 34]. Theyare indicative of air leaking through themouth or around the mask, but even withoutan air leak, patients can be troubled by thesesymptoms. Cold, dry air from the ventilator,often caused by a higher oxygen fraction,promotes the release of inflammatory medi-ators in the nasal mucosa, increases mucosalblood flow and thereby increases nasal airwayresistance and causes congestion. Treatmentoptions include the topical nasal applicationof saline, hyaluronic acid, steroids, decon-gestants or antihistamines, and regular mouthcare, as well as the addition of heat/moistureexchangers and an external heated humidifierto the circuit.

The use of active humidification of theinspired gas is mandatory for patients with atracheostomy, but its use in NIV is not alwaysnecessary. Nevertheless, it should be addedto the circuit with a low threshold, especiallyif leaks are present or a high oxygen fractionis delivered as it can attenuate the increase inresistance in the nasal mucosa, decreasedryness and enhance comfort and toleranceof mask ventilation [35]. It is also recom-mended to avoid thickened and tenacioussecretions. Gas temperatures during NIV donot need to be as great as for intubatedpatients and are to be based on patientcomfort (benchmark of 100% relative humidityat about 30uC) [36]. Heat/moisture exchangers

Figure 5Different self-cut hydrocolloid and gel sheets to beplaced between skin and mask. From left to right:Kerra ProTM (Crawford Healthcare Ltd, Knutsford,UK), Aderma (Smith & Nephew, London, UK) andGeckoTM (ResMed Ltd.)

Figure 6Foam and silicone sheets between mask and skin.



cannot be unconditionally recommended forNIV, because the additional dead space candecrease CO2 elimination and increase thework of breathing, which can become prob-lematic, in particular in hypercapnic ARF or ifthe delivered tidal volumes are very low [37].

Sedation

The topic of sedative medication to improvetolerance of the NIV interface is still contro-versial. The idea is to mitigate the patient’slevel of discomfort and obtain a level ofawake sedation without significant effects onrespiratory drive, minute volume, respiratorypattern, blood gases, haemodynamics andairway reflexes. The best way to improveinterface tolerance during NIV is still goodnursing and multidisciplinary care withintensive psychological support and reassur-ance of the patient. However, for somepatients who remain very anxious or agitatedwith the mask, a small dose of an anxiolyticmay be appropriate. Many pulmonary andcritical care physicians in North America andEurope are reluctant to use sedation becauseof the perceived risks of interfering with theability to protect the airway or depressingrespiratory drive [38]. Nevertheless, carefuland mild sedation in selected patients inICUs with a high nurse to patient ratio andspecial focus and attention on airway protec-tion and consciousness is usually safe, andcan sometimes help to prevent NIV failuredue to low tolerance. The ability to usesedatives or analgesics on wards with a lowerdegree of monitoring is very limited andcannot be recommended.

Acute-on-chronicrespiratory failure

The number of patients with chronic respir-atory failure who are on long-term home NIVis also constantly on the increase. Thesepatients are normally treated in specialisedcentres, but during acute exacerbations maypresent to the nearest emergency departmentor ICU for initial treatment. They will oftenbring their own mask and ventilator equip-ment with them and, while it is usuallynecessary to adjust the ventilator settingsduring the exacerbation, their mask cancontinue to be used. Although these patients

are ‘‘expert patients’’ concerning their maskmanagement and NIV, this does not implythat they will not have mask problems in theacute setting. Patients who are well adaptedto nasal masks or nasal prongs at homemight suddenly start mouth breathing duringthe exacerbation, which will necessitate atemporary switch to an oronasal mask or totalfacemask. The risk for facial pressure ulcerscan increase in the context of a more severeillness with, for example, worse oxygenationor lower blood pressure. Increases in pres-sure support can lead to air leaks andconsequently increased tightening of thestraps might follow. In addition, patientsmay suddenly find themselves on NIV formost of the 24-h period instead of only usingit at night, or be unable to correctly self-manage the mask because of weakness.These patients will have to be able tocontinue the treatment after the exacerbation,which can become very uncomfortable orpainful with a pressure sore on the face andprolonged wound healing due to complicatedpressure relief. Patients on home NIV canhave the same mask problems as all otherpatients in the acute setting and there is aneed for regular reassessment of mask fit,skin underneath the mask and headgear, riskfactors for pressure ulcers and for precau-tions to reduce the incidence of skin damageor NIV failure.

Feeding tubes, beards andother problems

NIV can be used with a nasogastric tube inplace and some masks incorporate a specialnasogastric tube adapter. If such a mask or aseparate nasogastric tube adapter is notavailable, padding of the tube and the skinunderneath the tube with a silicone dressingor other material is recommended to mini-mise air leakage and pressure on the skin.Regular reassessment of the skin under thenasogastric tube, in particular in the areawhere it is in contact with the mask frame,should be carried out and the position of thetube alternated if the treatment has to beprolonged.

Another frequent problem mainly asso-ciated with air leaks is beards. Shaving is avery quick and effective solution to thisproblem, but if this is inappropriate, anoronasal mask is usually more effective with



moustaches than nasal masks, and fullbeards can sometimes be managed betterwith nasal prongs, total face masks, or withhelmets in the ICU of an experienced centre.

Dentures can also become a problem, asa mask that fits very well with the denture inplace might not fit once the denture isremoved at night. It is important to be awareof this potential change in mask fit and tohave an alternative mask quickly available, ifneeded.

For patients who are unable to raise theirarms to pull the mask over their head or toreach the strap to remove the mask them-selves because of weakness, neuromusculardisease or severe arthritis, a quick-releasestrap can be added.

Droplet generation andairborne disease

NIV is a droplet-generating procedure, whichraises concerns about infection control andstaff protection with its use during outbreaksof diseases, such as pandemic influenza(H1N1) or severe acute respiratory syndrome,or with airborne diseases such as tuber-culosis. The amount of droplets falls signifi-cantly at a distance .1 m from the patient[39, 40], but healthcare workers who applyNIV have to stand close to the patient and,therefore, can be exposed to potentiallyinfectious droplets. The decision whether ornot NIV can be used in these situations, aswell as the general precautions to reducedisease transmission, usually depends onlocal infection policies. However, if NIV isapplied, a nonvented facial mask and filtered

exhalate can reduce environmental spread[39]. Also, fitting and securing the maskbefore the ventilator is turned on andsimilarly turning off the ventilator before themask is removed or lifted away from the faceis usually recommended.

Conclusion

Skills in mask fitting and prevention of mask-related problems are key components for NIVsuccess. Not all hospitals and NIV serviceswill be able to stock a large volume ofdifferent masks, which makes routine riskassessment for mask-related pressure ulcers,and knowledge and strategic use of skinprotective strategies even more important.Training programmes for NIV should impartthis knowledge and qualify the team to tailorinterface choice and preventive strategies toeach patient’s individual facial characteristicsand needs.

AcknowledgementsThe author is the recipient of a EuropeanRespiratory Society Fellowship (LTRF 2013-1798) funded jointly by the EuropeanRespiratory Society and the EuropeanLung Foundation. The author wishes tothank Anita Simonds (Dept of Sleep andVentilation, Royal Brompton and HarefieldNHS Foundation Trust, London, UK) forhelpful advice and critical review of themanuscript and Manuela Del Forno(Respiratory and Critical Care Unit,University of Bologna, Bologna, Italy) forher assistance with the pictures.

Educational questions1) Which of the following statements concerning mask choice is/are true?

a. Masks covering mouth and nose are more effective in improving blood gases than nasalmasks in acute respiratory failure

b. Oronasal masks are better tolerated and more comfortable than nasal masks in acuterespiratory failure

c. Oronasal masks are usually the first choice for NIV in acute respiratory failure in Europed. Mask switching is not recommended in the first 24 h of NIV in acute respiratory failure

2) Which of the following statements concerning interface-related pressure ulcers in NIV is/

are true?a. Pressure ulcers occur more often with oronasal than nasal masksb. A helmet cannot create pressure ulcersc. The use of skin protective dressings can reduce the incidence of pressure ulcers



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d. The most important strategy to prevent mask-related pressure ulcers is rotation ofdifferent masks

3) A 44-year-old woman, who is on home NIV because of an obesity hypoventilationsyndrome, presents to the emergency department with a chest infection and exacerbation ofher chronic respiratory failure. She has brought her ventilator and mask with her and isstarted on this with an increased inspiratory positve airway pressure (IPAP) and the nasalmask that she uses at home. At the higher IPAP, the patient develops a mouth air leak. Sherefuses to change the mask to an oronasal or total face mask because of claustrophobia.

Which of the following can be expected with a persistent mouth air leak?a. The expiratory volume increasesb. The intra-alveolar pressure is not influencedc. A further increase in pressure support can partly compensate for the leakd. Nasal airway resistance decreases.e. Heated humidification does not have an influence on nasal resistance in this situation

4) A 58-year-old smoker presents with an exacerbation of his chronic obstructive pulmonarydisease to the emergency department. He is tachypnoeic (respiratory rate 32 per min) and theinitial arterial blood gas analysis on room air shows pH 7.28, arteral oxygen tension (PaO2)50 mmHg and arterial carbon dioxide tension (PaCO2) 58 mmHg. He is started on nebulisedbronchodilators, steroids and antibiotics, and NIV is added with a facial mask and aventilator in the emergency department. He synchronises well with the ventilator, hisrespiratory rate decreases to 23 per min after 1 h, blood gases improve to pH 7.32, PaO2

64 mmHg and PaCO2 50 mmHg, and the patient feels better. He is transferred to a HDU andNIV is restarted with a smaller ventilator. The patient is awake, feels better and is still doingwell on the ventilator. There is no significant air leak, no signs of auto-positive end-expiratorypressure, patient ventilator asynchrony or pneumothorax, but the next arterial blood gasshows a pH of 7.29, PaO2 60 mmHg and PaCO2 of 65 mmHg. What is the most appropriatenext step?

a. Continue the patient on oxygen onlyb. Repeat the arterial blood gas analysisc. Check the equipment used (ventilator, circuit and mask)d. Intubate the patient immediatelye. Change to a nasal mask



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Suggestedanswers1) a. false, b. false, c.true, d. false2) a. true, b. false, c.true, d. false3) c.4) c.



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