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Amanda PiperGrant il~son

OR I G I .N A1 ARTI C.l E

Nocturnal n Isupport in the m nagementof daytime hypercrespiratory failur

Nasal ventilation is becoming increasinglyrecognised asan effective therapeutic strategyto minimise or correct hypercapnia in patientswith respiratory failure. Intervention may berequired on a shortar long term basis. In themajarityof patients, respiratoryfailure developsinitially during sleep. Assessing patients at riskof nocturnal hypoventilation, and institutingappropriate therapy, isbecoming an increasinglyimportant aspect of respiratorycare. This reviewoutlines methods and practices involved incommencing nasal ventilationtherapy. Twenty­nine patients presenting with hypercapnicrespiratoryfailurewere managed with nocturnalnasal ventilation over a 12 month period. Withthe use of this therapy PaCOzfell from 64(2) to50(1 )mmHg. (.Mean. (SE.; (.p.< 0.0.01 LWhi.le p.aO~improved from 55(2) to 68(2)mmHg(p <0.001 }during a mean ventilation time of 1O(O.8} days.Those factors which must be addressed for asuccessful program outcome are discussed.[Piper AJ and Willson GN: Nocturnal nasalventilatory support in the management ofdaytime hypercapnic respiratory failure.Australian Journal ofPhysiotherapy 42: 17-29]

Key words: Hypercapnia;Respiratory Disorders; Sleep;VentilationAJ Piper BAppSc(Phty), MEd is a seniorphysiotherapist and GN Willson BAppSc(Phty}aphysiotherapist at the Centre for RespiratoryFailure and SleepDisorders, Royal PrinceAlfredHospital, Camperdown, New South Wales.Correspondence: Amanda Piper, SleepDisordersUnit, BP5, Royal Prince Alfred Hospital,Missenden Road,Camperdown NSW 2050.

isability and death from chronicrespiratory failure andhypercapnia are commonly seen

in patients with neuromuscular andskeletal disorders affecting the chestwall. Until a decade ago, treatment forchronic respiratory failure of thisnature involved support of breathing,usually during sleep, with eithernegative pressure devices such as theiron lung or cuirass (Garay et a11981,Goldstein etaI1987),or with positivepressure through a tracheostomy(Hoeppner et alI984).However, bothforms of treatment involve majorlimitations and lifestyle modifications.The upper airway obstruction inducedby the suction effects of negativepressure devices (Ellis etall987) andthe increased morbidity andcomplication of care associated withthe introduction of tracheostomy haslimited the application of these twomodalities of therapy.In 1987, the first published reports of

the use of nasal positive pressureventilation (NIPPV) began to appearin the English literature (Ellis et al1987, Ellis et aI1988). The ability tocomfortably and effectively deliverpositive pressure through a face maskcame about from the development ofamask to deliver nasal continuouspositive airway pressure (NCPAP) topatients with obstructive sleep apnea(Sullivanetal 1981).

Since that time, the effectiveness andacceptability of nasal ventilatory

support for domiciliary use has beenconvincingly demonstrated and it isnow considered to be the first choiceof therapy for patients withneuromuscular and chest wall disordersrequiring home ventilation. The roleofnocturnal nasal ventilatory supporthas greatly expanded, and·now is beingused to manage patients withhypercapnic respiratory failure from awider range of pathologies in variousclinical situations. This paper outlineshow sleep disordered breathing canproduce abnormalities of daytimerespiration and function, then discussesthe experience and outcomes of nasalventilatory support in its variousapplications in clinical practice. As·themedical community becomesincreasingly aware of the role ofabnormal nocturnal breathing in thedevelopment of daytime respiratoryfailure and disability, lmowledge andskill in applying non-invasiveventilatory support will becomemandatory in the comprehensivemanagement of patients with chronicrespiratory failure. Physiotherapists arewell placed to contribute to theassessment and ongoing care ofpatients requiring this therapy.

Sleep and breathingInitially, abnormal breathing becomesapparent during rapid eye movement(REM) sleep, when there is spinalinhibition of all postural muscles,

ORIGli~AL ARTICLE AUSTRAliAN PHYSIOTHERAPY

From Page 17producing atonia of the accessory andintercostal respiratory muscles.. Thisleaves the diaphragm to provide thebulk of ventilatory effort.. Thebreathing pattern becomes irregular,especially during periods of phasic eyemovements. During this time, somedegree of hypoventilation is seen evenin normal subjects, whereby a 2-3 percent fall in oxygen saturation (Sa02)

and a 5-7mmHg rise in carbon dioxide(PaC02) can occur (Douglas 1984,Muller et al 1980). If the diaphragm isweak or working at a mechanicaldisadvantage, as in scoliosis, theindividual will be unable to generatesufficient pressure to maintainadequate ventilation. Oxygensaturation will then fall significantlyand PaC02 will continue to rise untilthe subject arouses. An arousal is ashort period of wakefulness (less than10 seconds), in which ventilation andpostural muscle activity is increased.During this time the accessory muscleswill be recruited and ventilation can berestored (Figure 1). The arousalresponse is a protective reflex tominimise alterations in blood gases.However, over time, sleep deprivationand fragmentation appear to blunt thisreflex so that higher levels of CO) andlower levels of oxygen are neededbefore arousal occurs. With longerperiods of abnormal breathing andhence deranged blood gases, the driveto breathe is also depressed not onlyduring sleep but eventually duringwakefulness as well, possibly as a resultof chemoreceptor adaptation (BerthonJones and Sullivan 1987, Garay et al1981). This sets up a vicious cycle ofdepressed drive to breathe, greaterperiods of abnormal breathing andmore sleep fragmentation, to the pointwhere respiration is grossly abnormalboth at night and during the day.Without intervention, disability anddeath from hypercapnic respiratoryfailure will eventually occur (Piper andSullivan 1994a).

There is no simple daytime testavailable to determine if nocturnalhypoventilation is present and to whatdegree. Serial daytime arterial bloodgases, along with spirometric and

Figure 1.Part of a sleep study recording from a patient with Duchenne muscular dystrophy. Therecording channels include: electoencephalogram (EEG), electrooculogram (EOG),electromyograms of the genioglossus (EMGgg), diaphragm (EMGdia), sternomastoid(EMGst) and abdominal (EMGabd) muscle groups. During non-rapid eye movement(NREM) sleep (Panel A), recruitment of the sternomastoid muscles during inspiration andthe abdominal muscles during e}q]~ration occurs to rnaintain chest wall movement Withthe onset of rapid eye movement (REM) sleep (Panel B), marked reduction in accessorymuscle activity results in a reduction in chest \Nall movement until arousal. Althougharousal permits the reactivation of the accessory muscles and recovery of ventHation, italso causes sleep disruption.

AUSTRAliAN PHYSIOTHERAPY

inspiratory muscle strengthmeasurements, areinaportantindicators of the likelihood thatnocturnal hypoventilation may bepresent. However, only sleep studiesmonitoring respiratory variables canconfirm this (Bye et a11990, Piper andSullivan 1994a).

Indications for nasal ventilatorysupportNasal ventilatory support provides ameans by which abnormal breathing atnight can be corrected in a non­invasive fashion. Generally, thetechnique is well accepted by thepatient, who will continue to becompliant with treatment if theinconveniences involved (ie using amask) are compensated for byimprovements in exercise toleranceand overall sense of wellbeing.However, it is becoming increasinglyclear that the usefulness of nasalventilatory support is not confinedsimply to those patients with chronic

ORIGINAL ARTICLE

respiratory failure from chest wallrestriction requiring home ventilation.The technique is now being seen as arealistic alternative to invasiveventilation in a number of clinicalsituations, and can be offered topatients for whom treatment waspreviously considered inappropriatebecause their condition was regardedas endstage and therefore hypercapniawas inevitable (Table 1).

Chronic respiratory failureUse of nasal ventilatory support isindicated for patients with symptomsof hypoventilation and daytime CO2retention as a consequence of a widenumber of disorders affecting themuscles or the mechanics of the chestwall. Its role in patients with chest walldeformity (such as scoliosis orthoracoplasty) and stableneuromuscular disease (poliomyelitis,various myopathies, spinal muscularatrophy and spinal cord trauma) hasbeen well established with almost 10

years of experience with thesedisorders. Use of nasal ventilatorysupport nocturnally has been shown toimprove daytime blood gases (Ellis eta11987, Leger et al 1994), sleep quality(Elliott et a11992, Ellis et a11987, Elliset al 1988 ), and exercise tolerance(Carroll and Branthwaite 1988). Incontrast, use of oxygen therapy in suchpatients is rarely successful long term(Garay et a11981) and indeed maycontribute to the problem of nocturnalCO2 retention by prolonging theperiods of abnormal breathing(Figure 2).

A more controversial indication forNIPPV is its use in patients withchronic airflow limitation (CAL).Elliott and co-workers (1992)investigated the feasibility ofdomiciliary NIPPV in 12 patients withstable hypercapnic respiratory failureand CAL, looking at its effects on sleepand quality of life. At 12 months, sevenpatients continued to use the device ona regular basis, and at the completionof the study requested to remain onnocturnal ventilatory support becauseof the symptomatic improvement theyhad experienced. Mean nocturnal Sa02and transcutaneous carbon dioxide(TcC02) improved considerably withtreatment. However, not all reports onCAL patients have been favourable.Strumpf and co-workers (1991)enrolled 19 patients with CAL into arandomised, crossover designed studycomparing three months of nocturnalventilatory support using a bi-Ievelpositive pressure device (BiPAP,Respironics, Murrysville, USA) with"standard care". Only seven patientswere able to complete both arms ofthis study, and the authors reported nobenefit from BiPAP treatment in termsof improvements in gas exchange orpulmonary indices. The differences inresults possibly arise from patientselection in the various studies. Itappears that the sub-group of patientswith CAL likely to show improvementfrom this form of therapy are thosewith high levels of daytime CO(Elliott et a11991, Hill 1993) who havedemonstrated severe respiratory gasexchange abnormalities during sleep(Elliott et a11992) and who are

~

figure 2.Slow recording of oxygen saturation (Sa~2) and transcutaneous carbon dioxide (IcC02) ina patient with neuromuscular disease. With the addition of supplemental oxygen,baseline Sa02 (solid line) is improved but at the expense of acute CO2 retention (dashedline).

19unresponsive to maximal conventionalmedical therapy. It also appears thatacclimatisation to the technique andadequate patient education areessential elements for the success ofthis treatment long term, with thosepatients who are admitted to hospitalfor at least a few days to becomefamiliar with the technique (Elliott etal 1992) doing better than thosetreated as outpatients (Strumpf et al1991).

Acute respiratory failure

With the success of mask ventilatorysupport in patients with chronicrespiratory failure, many centres arenow assessing its use in patients withacute respiratory failure. Reports of theuse of this technique in patients withCAL (Brochard 1990), chronic heartfailure (Benhamou et al 1992),pneumonia (Meduri et al 1989), post­operative difficulties (Pennock et al1994) and pulmonary oedema(Lapinsky et a1 1994) have all appearedin the recent literature, with successrates between 70 and 80 per centreported (Hill 1993).

Exacerbation of CAL is the mostcommon cause of acute respiratoryfailure in the majority of the stpdiesreported (Bott et al 1993, Brochard etaI1990). Favourable outcomes withthe administration of NIPPV to thispopulation have included the successfulavoidance of endotracheal intubation,improvement in gas exchange, reducedlength of intensive care stay andreduced mortality.

Negative outcomes have also beenreported (Foglio et a11992), althoughthe ventilation protocol wasintermittent, with the patient using themachine a couple of times a day forvarying periods. In those studies withmore favourable results, the patientsused ventilatory support almostcontinuously, including sleep periods,until their clinical status had improved.Since the most severe alterations inventilation and blood gases will occurduring sleep (Bye et al 1990, Piper andSullivan 1994a) it seems reasonablethat ventilatory assistance used during

ORIGINAL ARTICLE

this time will be most likely to produceclinical improvements.

For patients with acute exacerbationsof underlying respiratory problemssuch as CAL, use of nasal or full facemask ventilation allows theadministration of higherconcentrations of oxygen to correcthypoxia without causing unacceptablerises in hypercapnia (Conway'et al1993), and stabilises the patient'scondition until the acute events arereversed. Although arterial oxygentensions are improved and COzcontrolled in most patients, in thosewith severe hypercapnia, further riseswith the initiation ofNIPPV may beseen (MeechamJones et aI1994).Therefore, intervention with nasalventilatory support in this populationmust be used with caution, and shouldbe seen as an adjunct to conservativetherapy or when intubation andmechanical ventilation is consideredinappropriatee

The application of mask ventilationhas been described as a difficult andtime-consuming procedure (Chevroletet aI1991). Although the techniquerequires more skill than the applicationof oxygen therapy, the availability ofcontinuous monitoring devices forSaO and TcCOz as well as stafffamiliar with the technique and skilledin its application, have seen this

AUSTRAliAN PHYSIOTHERAPY

technique developing as an effectiveand safe alternative to invasiveventilation. This allows treatment tobe carried out on a general respiratoryward (Elliott et al1990, Piper et al1992). In many patients, exhausted bytheir deteriorating condition andinability to sleep for prolonged periodsbecause of abnormal breathing, theintroduction of mask ventilation willrelieve hypoxia and hypercapnia andreduce the respiratory work, allowingthe patient the chance to achieve longperiods of deep sleep. Once this isachieved, little nursing care is required,although careful monitoring for safety,adjustments to ventilator settings andreduction of mouth and mask leaks willbe necessary to ensure that the bestlevel of ventilation is achieved.Appropriate patient selection and skillwith the technique are necessary forthe technique to be effective. Thepatient needs to be cooperative and notat risk of aspiration (Batt et a11993)and should be able to clear secretionseffectively either on their own or withassistance (Elliott et alI990). Duringventilation for acute respiratory failure,ventilatory assistance may be requiredfor most of the 24 hour period, withthe mask being removed for shortperiods only to allow speech, coughingand so on. As the patient's conditionimproves, periods on the machine arereduced as tolerated, although

Figure 3.Mouth leaks may cause significant loss of ventilation especially with volume presetdevices. In this patient with poliomyelitis, good support of ventilation occurred duringwakefulness with the patient's mouth closed (indicated by black bar), andtranscutaneous carbon dioxide (1cCOz) levels fell (dashed line). However, with the onsetof sleep, the patient's mouth opened, .·educing ventilation and TeC0

2rose. The patient

woke, closed the mouth, and TcCOzfeU again as ventilation improved. This continuedthroughout the night until a chinstrap was added. The patient was receivingsupplemental oxygen during ventilation, so oxygen saturation (SaOz) was insensitive ingauging the effectiveness of ventilatory support.

AUSTRAliAN PHYSIOTHERAPY

nocturnal ventilation may continue forsome time and may be necessary on along term basis.

Weaning fromconventional ventilationFor a small number of patientsrequiring intubation and mechanicalventilation, withdrawal fromventilatory support will pose a clinicalproblem. This is most likely to be seenin patients with pre-existingrespiratory pathology, where increasedwork of breathing or impairedrespiratory drive already exists (Marini1991).

Several published reports havedescribed the value ofNIPPV inweaning patients from invasiveventilation. Restrick et al (1993b)reported 14 patients with weaningdifficulties who were commenced onNIPPV after extubation or when thepatients were being supported bysynchronised intermittent mandatoryventilation (SIMV) with a rate of lessthan five breaths per minutew Theseauthors reported an 87 per cent successrate with this technique. Udwadia et al

ORIGINAL ARTICLE

(1992) used NIPPV to facilitateweaning in a series of 22 patients andwere able to successfully wean 20patients from invasive support. Thesuccessful transfer from tracheal tonasal ventilatory support has also beenreported in patients requiring longterm nocturnal ventilatory support(piper et aI1994b)."In patients where weaning difficulties

become apparent or are anticipated,nasal ventilation can be used to assistbreathing in order that reintubation isavoided or progression totracheostomy is not required. Evenwhen tracheostomy has occurred andventilatory support is required onlyintermittently, use of nasal ventilationcan allow the removal of the tube,which can improve spontaneousbreathing (Criner et al 1987) andreduce the complication of care such assuctioning and communication.

Devices for non-invasiveventilatory supportUntil a few years ago, the majority ofdevices available for home ventilationwere volume preset (for example PLV

100, Lifecare, Boulder CO). Withthese devices, a guaranteed tidalvolume is delivered from the machinein the absence of a leak, with peakinspiratory pressures varyingdepending on the patient's chest walland lung compliance. These machinesare usually used in either assist-controlor control mode. At our centre, theassist-control mode of operation,whereby the clinician sets therespiratory rate of the machine tocapture that of the patient, is preferredbut if the patient requires anyadditional breaths, these will bedelivered.

More recently, pressure presetdevices designed for noninvasiveventilatory support have becomeavailable (BiPAP, Respironics,Murrysville, Pennsylvania; VPAP,Rescare, Sydney), and are gainingpopularity due to their simplicity,lower cost and comfort. These bi-Ievelairway pressure devices cycle betweentwo levels of pressure. Duringinspiration a preset pressure (IPAP) isgenerated, which terminates when acertain time has elapsed (usually 3seconds) or if flow falls below apercentage of the peak inspiratoryflow. End expiratory pressure (EPAP)is maintained at a lower level, and is setaccording to the need for upper airwaysplinting. With the BiPAP device, themost commonly used machine, threedifferent modes ofventilatory supportare available. The VPAP deviceoperates in the spontaneous modeonly. In the spontaneous mode, thepatient determines the respiratory rateand inspiratory time. In thespontaneous timed (SIT) mode, theoperator sets a minimum rate, wherebythe machine will deliver backupbreaths if the patient rate falls below acertain frequency. In the timed mode(T), the machine is set to deliver allbreaths, determining not onlyrespiratory rate but also inspiratorytime. The tidal volume the machinedelivers will depend on the differencebetween the IPAP and EPAP settings,and the interplay between thesepressures and chest wall compliance(MeechamJones and Wedzicha 1993).

Comparison studies examining the -

ORIGINAL ARTICLE AUSTRAliAN PHYSIOTHERAPY

From Pageefficacy of the volume cycled andpressure preset machines are few(MeechamJones and Wedzicha 1993;Restrick et aI1993a). However, itappears that both devices can providesimilar quality ventilation in patientswith low or normal chest wallimpedance. In patients requiring highinflation pressures due to low chestwall or lung compliance, volume cycledventilators appear to be more likely tocontrol nocturnal blood gases than theBiPAP device (Simonds and Elliott1994).

Implementing and monitoringnasal ventilatory supportFor patients with chronic respiratoryfailure, the clinical practice at theRoyal Prince Alfred Hospital Centrefor Respiratory Failure and SleepDisorders is to admit the patient tohospital for the inirial trials ofventilation in order to maximise theeffectiveness and minimisecomplications associated with thetechnique. Practice sessions during theday provide an opportunity to becomefamiliar with the mask and the deliveryof air from the machine. Initialmachine settings are based on thepatient's level of comfort and theirdaytime breathing characteristics.Once the patient is acclimatised to thetechnique, ventilator parameters areadjusted to achieve the most effectivelevel of ventilatory support, based onSaO and CO2 levels. The patient isthen

2introduced to the device for

nocturnal use, again with at least 8a02and TceO monitoring as basic guidesto the effedtiveness of the technique inmaintaining ventilation. Oncenocturnal ventilation is established,early morning arterial blood gases aretaken to verify that ventilatory supporthas been effective overnight.

In the acutely unwell patientpresenting with an acute deterioration,ensuring suitable settings andsynchronisation between machine andpatient is imperative both for the safetyof the patient and for a positiveoutcome to therapy. In this situation,monitoring of SaO

Jand TcC02 needs

to be supplemente by arterial

~-_.""......Figure 4.The top panels illustrate non-rapid eye movement (NREM) and rapicl.ey~ mov~ment (~EM)

sleep in a patient with chronic airflow limitation and REM hypoventllatlon USU1Q a bllevelventilatory support device in the spontaneous mode. Abbreviations are the same as th~se

used in figure 1, with the addition of oxygen saturation (Sa02) and pressure (representingthe inspiratory and expiratory phases of the machine, with inspj~ati~n indi..cated ~V an lipdeflection). Poor synchronisation between the patient and maclune IS ObVIOUS, withsignificant desaturation in REM sleep. The lower panels demonstrate the improvedsynchronisation and ventilatory support provided by the machine when a chinstrap wasused to minimise mouth leal<s.

AUSTRAliAN PHYSIOTHERAPY ORIGINAL ARTICLE

provides information about the qualityof the breath delivered and problemssuch as leak or upper airwayobstruction which may occur duringtreatment.

The most commonly observed eventlikely to affect the adequacy of maskventilation is mouth leaks. Althoughthe pressure preset devices are said tobe more effective in compensating forthese leaks (Braghiroli and Donner1992), clinically we have foundsignificant leaks can occur with eitherdevice" The BiPAP device may sensethe mouth leak as patient flow andtherefore maintains IPAP for up to themaximum 3s periodG In severe cases,only every second or third breath willbe supported, which can produce poorventilation and oxygen desaturation.With volume preset devices, peakinspiratory pressure will drop in thepresence of mouth leaksG Robert et al(1991) found that when patients aremonitored nocturnally, mouth leakswere observed 100 per cent of thetime, although the effect on ventilationefficacy was variable. Mouth dryness isindicative of significant mouth leakswith both types of devices, and can berelieved by the use of a humidifier (egHe 100, Fisher and Paykel, NZ).However, attention to the underlyingproblem, that is, minimising mouthleaks, is a more sensible approach tothe problem and will often lead tobetter augmentation ofventilation(Figure 4)G

Clinical experience with non...invasive ventilatory supportIn the following section, the use ofnasal ventilatory support in apopulation of patients withhypercapnic respiratory failurepresenting to a respiratory medicalward is reported to demonstrate howthe technique is used in clinicalpractice and to outline some of thepractical issues likely to beencounteredG It should be noted that avolume preset device was used for allpatients, as that was the only type ofventilator available when this study wasperformedG However, many of thepatients described would now betrialled on a pressure preset device. -

·.·1····················1·····

sleep. It needs to be understood thatthe response-latency with TcCO is. zprolonged (up to three ffilnutes), andalthough this device does not permitthe recording of transient alterations inCOz' progressive CO2 rises fromIJ)outh leaks (Figure 3), or hypocarbiafrom overventilation will be detected.

Titration of inspiratory andexpiratory pressures for patients on apressure preset device or tidal volumefor a patient using a volume cycledventilator is made on the basis ofmaintaining or improving saturationand carbon dioxide values whilstensuring patient-ventilator synchronYGRecording of chest wall movement (forexample with inductiveplethysmography or strain gauges) ormeasurement of diaphragm activitywill provide essential informationabout the patient's spontaneousbreathing efforts and the delivery oftidal volume or pressure from theventilator. Airway pressure is a valuableparameter to measure, particularlywith volume preset machines, as it

~O,:'-,:'

\il::;:;:,

figure 5.Changes in daytime partial-pressure of arterial oxygen (PaC) (solid circles) and carbondioxide (PaC02) (solid stars) with the introduction of short...te

2rm nasal ventilation. Data

are mean (SE)G NIPPV - Nasal positive pressure ventilation.

punctures to ensure the adequacy ofventilatory support so that decisionsabout alternative methods such asintubation can be made quicldYGMeduri et al (1991) demonstrated thatif gas exchange failed to improvewithin the first few hours ofcommencing ventilation, later successwas unlikelYG

The parameters monitored duringnasal ventilation in the hospital settingwill depend greatly on the equipmentavailable, the preferences of theclinician setting the device, and theaim of theraPYG As stated previously,our unit considers SaOz and TcCOmonitoring as fundamental zmeasurements in ensuring theadequacy and safety of nasal ventilatorysupport.lIovvever, there is somedebate in the literature regarding theaccuracy ofTcCOz monitoring in thispopulation, particularly with highlevels of COz (Sanders et al 1994). Inour experience, TcCOz monitoring hasbeen invaluable in reflecting trends inventilation, both awake and during

Figure 6.Awake daytime partial pressure of arterial carbon dioxide (PaCOz) values prior to(hatched bars) and after (clear bars) the commencement of NIPPV for each of thediagnostic groups treated. Due to the small numbers of patients with chest wall disordersseen (n =3), statistical analysis was not performed. Error bars indicate SE.

from PageMethodsThe records of 29 consecutive patientsreferred to our unit for maskventilation over a 12 month periodwere reviewed. Respiratory failure inthe patients seen was due to a range ofcauses: six patients presented withneuromuscular disease, three had chestwall dysfunction, 13 had obesity­hypoventilation (ORS) unresponsiveto conventional CPAP therapy andseven patients had end stage lungdisease (chronic airflow limitation orcystic fibrosis). The clinical conditionand histories of all patients suggestedthat an element of sleep disorderedbreathing was contributing to theirrespiratory failure. Twenty-twopatients underwent full sleep studiesimmediately prior to commencingmask ventilation, and confirmednocturnal hypoventilation withsignificant CO2 retention" Sleep studieswere performed using standardtechniques and included monitoring ofelectroencephalographic (EEG) andelectrooculargram (EGG),electromyographic (EMG) activity ofthe genioglossus and diaphragm, nasalairflow, chest wall movement, Sa02and TcC02• All variables wererecorded continuously on a 12 or 16channel polygraph.

The decision to commence non­invasive ventilation was made in one ofthe following circumstances:a) acute respiratory decompensation

despite maximum conventionaltherapy, where intubation andlCU management was deemedinappropriate, usually becausedifficulties in weaning wereanticipated;

b) failure to respond to CPAPtherapy due to tolerance, or failureof the device to prevent significanthypoventilation with markedworsening of hypercapnia duringsleep and/or failure to reversedaytime hypercapnia; and

c) stable chronic respiratory failuredue to hypoventilation duringsleep in neuromuscular or chestwall diseases.

ORIGINAL ARTICLE

Ventilation techniqueMask ventilation was commenced on ageneral respiratory ward withcontinuous monitoring of SaQ) andTcC02 to guide the settings otventilation parameters and ensure theadequacy of the technique. In general,ventilation was recommended fornocturnal use only, with short daytimesessions to familiarise the patient withthe technique. However, if patientswere obnmded or exhibited signs offatigue, ventilatory support was usedcontinously until the patient's clinicalcondition improved. A volume-cycledventilator was used (PLV-lOO, MedicalGases ofAustralia), with anappropriately chosen commercial nasalmask (Sullivan™, Rescare, Sydney). Inthe deeply obtunded patients, a fullface mask was necessary if significantmouth leaks could not be controlled bya chin strap. The assist/control modeof ventilation was used and, wherepossible, the patient was slightlyhyperventilated in order to capture andcontrol respiratory pattern. A positiveend expiratory pressure (PEEP) valvewas added to the expiratory port of theventilation tubing if residual upper

AUSTRAliAN PHYSIOTHERAPY

airway obstruction was noted.Prior to commmencing ventilation,

arterial blood gas measurements(ABGs) were taken in the late morningor during the afternoon from the radialartery, with the patient awake and, ifpossible, breathing room air.Additional blood gas sampling wasperformed at 0600 hours with thepatient on the ventilator to check theefficacy of overnight ventilation and tocheck for any drift in the reading of theTcCOz monitor. Blood gas valuesreported were obtained prior tocommencing ventilation and againprior to hospital discharge, and withthe patient breathing spontaneously.

StatisticsData are presented as mean(SE).Comparisons between measurementstaken prior to ventilatory support andafter stabilisation were made usingpaired t tests. Comparisons madebetween patients presenting with acuteand chronic respiratory failure weremade using unpaired t tests.Differences between diagnostic groupswere analysed using analysis ofvariance for repeated measures.

AUSTRAliAN PHYSIOTHERAPY ORIGlr~AL ARTICLE

::::::::,::<::,::::

ResultsClinical outcomesIn all patients, significantimprovements in ABGs were achievedduring the hospital stay. As a group,PaC02 fell from 64(2) to 50(1) mmHg(p < 0.001), while PaOz improved from55(2) to 68(2) mmHg (p < 0.001)during a mean ventilation time of10(0.8) days (Figure 5). Analysis of dataaccording to patient diagnosisdemonstrated that all subgroupsresponded with a similiar fall in PaCOzand improvement in PaOz after theintroduction of nasal ventilation(Figure 6, Table 2). In looking atresponse to treatment based onwhether the patient presented withacute or chronic respiratory failure,both groups responded similarly. Asexpected, patients presenting withacute decompensation (ARF) had asignificantly higher PaC02 level thanpatients with chronic stable respiratoryfailure (CRF) (73(3) vs 58(2) mmHg,p =0.001). However, after ventilation,there was no difference in CO2 levelsbetween the two groups (52(3) vs 49(1)mmHg, p =0.42) (Table 3).

There were no differences in theventilator settings used for patientspresenting with acute respiratoryfailure compared with chronicrespiratory failure (Table 3). However,there were differences in the peakairway pressures required to ventilatethe two groups effectively. Patientswith acute respiratory failure requiredsignificantly higher inspiratorypressures to maintain effectiveventilation during sleep (ARF: 28(1)cmH20 vs CRF: 23(1) cmH20,P=0.009).

In patients with primary lung disease,higher tidal volumes with greater peakairway pressures were required toachieve acceptable ventilationcompared with the other diagnosticgroups (Table 4), with a greaterlikelihood of air leakage, particularly

~

Differences were considered significantat the 0.05 leveL Analysis wasperformed using the Excel statisticalpackage (Microsoft, Version 5).

(tOOl

0.9

51« (4) 58:,:'(3} 0.19

>'/< to',::': 1;::'.),':.'.",.:i :/':': I,66 (3) 0.3371 (4)

Be .. 20 £n~~.(nij)..ea.dis.~"ll:< , ............ ;: ......... ,,:;............":':>... '!: ,'"

aaseliti.~ 'Pa02(iiliDHJ1' ,'11t~~~~nt::l>a02.<~g), "".biWle PaGO:.f 73 (3) 58 (2)(D.1iil.Hg) ';

<: :::,<:, ,:'.

::::;Ofhaselihe·andpost ·ventilation••b.IOOdg"j.f~~ the.groYQ:~,I!~ng .tp

patj~ntdiagnbsjs. All dAta are presented as mean (SI:),:;,:. .. I::i:i'::":::'::::::::::::::}::::::i]:::::]::]

Dii.gp.Qsis', No ~e, Imtial Imti,~l, ':~~s~ ,' P~~,~'>'-.</:" ," '" ~entllitton' ,V"~tituitibtr '

P~()i Ra<Z~~: ,::i:,':?Pi0t ' ,p$@~i::;;;:::[!H"(~g) 'mmJlg) , ,'(tmmg) '<Hlqg);i:)!\:]:;>

'Scoliosis :3 54' €9) ,, 5:1 Ci) 63 ,(9) 66 (2) 4li (2)'::,,;:<'Neuromuscular 6 44 f7) 65 (7) 55 (~~ 80 (4-) 49 (q)0MS 13 50 (3) ,48(2) ,62',(20 62 (3): ;4;>*.. :"<t>lo;'>::'.,,:,,::,,.::,:--:> >1

JS~;uig'mi$ease '/1 ,'3 <~ ,~1 <5~* 78 (5J 72 (8)* 61 (4)::/:;:::::::;:1':::/::Mean (SE) 29 53' (3) 55 (2) 64 (2) '68 (zy 50 (~):::i:::::/i:::::::::i::

'1Jj)enot~spatients on ddditional o~gf(n w.hen blt.i&dl~s tak~n. 1:;1:':"::111.Qlil8,:'4?:(JJll(lsitj;',lJJflo1)efftiJ(Jtion,syn/drome. .

..~:s~::::::r~~::':~a:is~~ paiientspreseniing witbeitbetae_ or Cb~i~....?::"::""";::.;::',':;;':':'

from Page 25through the mouth, and a higher riskof air swallowing. Despite this,significant improvements in PaC02were achieved in these patients, with afall in PaCOz from 78(5) to 61(2)mmHg after ventilation (p =0.007).However, the PaCOzlevel postventilation remained significantlyhigher than for other groups

.(P(2Sl) = 10.01; compared with OHSgroup: t(7) = 5.96;p < 0.001; comparedwith neuromuscular group: t(9) =2.96;P< 0.009).

Often, clinical and subjectiveimprovements were seen within thefirst day or two of commencingNlPPV, with physiologicalimprovements following several dayslater. In those patients where fullpolysomnography was performed onthe first night of ventilation (n =6),long periods of slow wave (SWS) andREM sleep were seen, despite mouthand mask leaks and the novelty of thesituation for the patient.In all patients, commercially available

masks were used. Full face masks wereneeded by three patients to minimisemouth leaks. One patient found thenasal mask claustrophobic and nasalprongs (Adam Circuit, Puritan BennettCorp, Lenexa, Kansas, USA) were usedin this instance. In 21 patients, nasalclips or "Bubble" cushions (Sullivan™,Rescare, Sydney) were utilised tominimise mask leaks whilst exertingminimal pressure on the skin.

The technique was well accepted,with 23 of the 29 patients sleepingmost of the night on the device by thesecond night of therapy.ComplicationsSide effects caused by the techniquedid occur, but these were minor anddid not prevent the patient fromcontinuing with ventilation. Airswallowing with abdominal distensionwas the most frequent complaint,occurring in seven of the 29 patients.The other group of problems relatedto leaks from the mouth or mask.These were managed by changing themask type or introducing a chin strap.Twenty-four of the 26 patients using anasal mask or nasal prongs required achin strap.

ORIGINAL ARTIClE

Post-hospital managementPrior to hospital discharge, 15 patientswere transferred to nocturnal CPAPtherapy, with six of these also requiringsupplemental oxygen. In anotherpatient, nocturnal oxygen alone wasprescribed. The remaining 13 patientscontinued on nasal ventilation on adomiciliary basis in order to maintaindaytime blood gases and preventnocturnal hypoventilation, after sleepstudies showed that nocmrnalhypoventilation persisted and couldnot be controlled by oxygen and/orCPAP.

DiscussionThe results of this study demonstratethat nasal mask ventilation is aneffective and well-tolerated method ofreversing or minimising daytimecarbon dioxide retention. Thetechnique can be carried out on ageneral ward, and can be used forshort-term continuous support orlong-term nocturnal treatment ofpatients with either chest wallrestriction or airway obstruction.In all patients reported in this present

study, significant improvements inPaCO occurred whilst in hospital,regardless of the underlying diagnosis.These findings differ somewhat fromGay and co-workers (1991) where only

AU STRAllAN PH YSlOTH ERAPY

minor changes in daytime CO2 valueswere achieved in their patients duringhospitalisation. Part of this differencemay have been our greater use of chinstraps to minimise mouth leaks andtherefore optimise ventilationnocturnally. Gay and co-workers(1991) reported that only six of their26 patients wore chin straps, whereas24 of our 26 patients using nasal masksor prongs wore one, with the otherthree patients using a full face mask.Although some patients may not beable to tolerate chin straps initially,once they were familiar with thetechnique, chin straps, in general, werereadily accepted. Air leaks at theinterface betw"een face and mask orthrough the mouth commonly occurand are often unavoidable. With thistechnique, some air leakage has to beaccepted as long as effective ventilationis maintained and the leakages do notcause frequent arousals from sleep. Wehave found that leaks frequentlydecrease as the patient becomes moreaccustomed to the device.To a large extent, the efficacy of the

technique and the tolerance of thepatient to it depends extensively onmaximising the effectiveness ofventilation whilst minimisingproblems. Various studies from otherunits overseas report a rate of failure ofpatients to tolerate NlPPV therapy of

AUSTRAliAN PHYSIOTHERAPY

between 19 and 36 percent (Gay et al1991, Strumpf etaI1991).This has notbeen our experience in either short orlong term follow up series. The betterresults reported here may reflectdifferences in patient selection,therapist input, or our more aggressiveapproach to minimising mouth leaksand maximising ventilation.

Unlike many colleagues overseas, wehave experienced few problems withthe discomfort or skin damage sofrequently attributed to commerciallyavailable masks. Bach (1992)commented that commerciallyavailable masks may not be adequatefor the higher flows needed forventilation and suggested that custommoulded interfaces needed to beconstructed for about 50 per cent ofpatientsusingNIPPV. However, sucha task is more cosdy, time consumingand requires a certain degree ofexpertise, which may deter those newto the·area from trialling this non­invasive technique. In the presentstudy, all patients were ventilated usingcommercially available masks. In themajority of cases, Bubble masks orclips were necessary to provide greatestpatient comfort and leak minimisation.However,the need for a comfortableand effective full face mask remains,particularly for use duringmanagement of acute respiratoryfailure.

It is important to recognise that thefirst few nights ofsleep on theventilator will be different fromsubsequent sleep, and for that reasonthe patient should be monitored andobserved closely during the initial trialsof nasal ventilation. Rebound of slowwave and REM sleep, along withdepression of arousal responses whichcan occur during initial treatment trials(BerthonJones and Sullivan 1987,Piper and Sullivan 1994a) requirescareful observation and supervision ofthe patient to ensure the efficacy of thetechnique and the safety of the patient.

Side effectsA number of adverse effects have beenreported with the use ofnasalventilation. In most cases, theseproblems pose an inconvenience to thepatient but generally do not cause

oRIGI NA 1 ART I C LE

treatment to be abandoned. However,ifthese problems can be addressed andsolved, quality oflife and satisfactionwith treatment long term will beimproved.

Gastric distension caused by airswallowing is most commonly seen inpatients with low chest wallcompliance (such as lung disease) orwith weakness ofthe gastric sphincter.Up to 50 per cent of patients onvolume preset ventilators may reportgastric distension ·at some time duringtreatment (Leger 1994), although it isless likely to be seen with pressurepreset devices. The administration ofpeppermint water prior to sleep,sleeping with the left side down andmaintenance of minimum effectiveventilator pressures are all usefulstrategies to combat this problem.Dryness of the mouth suggests oralleakage, and although it can bemanaged with humidification,attention to minimising the leak canalso improve ventilation efficacy.

Patient educationAlthough nasal ventilation is aneffective treatment for hypercapnicrespiratory failure, it should not beassumed that it is either appropriate orsuitable for all individuals.. Beforeinstituting long term home therapy,consideration must be given to thepatient's overall clinical picture, theircoping mechanisms and degree ofsocial support. In those patients withprogressive disorders, such as motorneurone disease or Duchenne musculardystrophy, frank discussion about theongoing development of respiratorymuscle weakness, and therefore thepossibility ofventilator dependence, isessential. In these patients,the primaryaim of nocturnal ventilatory support isto improve daytime.symptoms andoverall quality of life, rather thansimply prolonging survival. Discussionabout commencing nocturnalventilation must also raise issuesregarding the patient's wishes withrespect to eventually extendingventilator use into the daytime. Thisincludes eventual ventilatordependence or palliative care measures,and the implications of a tracheostomyfor someone with upper limb paralysis

and possible bulbar dysfunction. Suchdecisions are difficult but need to beconsidered outside of an emergencysituation, as once a tracheostomy isperformed it cannot always be easilyreversed in these patients. We havefound that many individuals and theirfamilies in this situation are notprepared for the limitations such aprocedure can have on lifestyle,resources and quality oflife.

Follow upAcceptance of this form oftherapy inboth the short and long term dependsgreatly on relieving or improving thepatient's symptomatology whilstminimising the side effects andinconveniences of the treatment. Forthe majority of patients, the benefits oftherapy outweigh the inconveniences,with compliance rates of 90 percentbeing reported in follow up (Potter etaI1994). This is substantially higherthan compliance rates for mask CPAPin patients with obstructive sleep apnea(Kribbsetal 1993). Once commencedon treatment, regular follow up isnecessary to review ventilation. settingsand check the functioning ofequipment. Over time, ventilationrequirements and settings can change,particularly if patients have underlyingpathology which is progressive, ifweight is gained or lost, or if upperairway obstruction develops.

Daytime blood gases and lungfunction provide limited informationabout overall.progress. Full nocturnalpolysornnography will identify moresubtle problems and technicaldifficultieswhich.may be causingdaytime symptoms. This is particularlyimportant for .patients with progressivedisease, to distinguish betweenprogression of their primary diseaseprocess.and problems of inadequateventilation.

ConclusionOver the past decade, non-invasivenocturnal ventilatory support hasemerged as an effective and acceptablemethod of reversing daytimehypercapnia and improving the clinicalcondition and quality of life in patients...

ORIG I r~ A l ART I C LE AUSTRAliAN PHYSIOTHERAPY

from Pagewith a wide range of pathologiescausing nocturnalhypoventilation.With the continued development ofventilatory support devices andinterfaces, the technique is becoming areasonable treatment option forpatients with both acute as well aschronic respiratory failure.. Anunderstanding of the various devicesavailable, and the problems likely to beencountered with each, is becoming anessential skill for any professionalworking with patients with respiratoryinsufficiency. Physiotherapists are wellplaced to be part of that team, in boththe assessment.andmanagement ofpatients with established respiratoryfailure or those at risk of developing it.This technique can be used as part ofan overall respiratory care program togreatly enhance the care of patientswith hypercapnic respiratory failure.

AcknowledgementsWe thank the nursing and medical staffof Ward BP5, Royal Prince AlfredHospital.. We are also grateful to DrRon Grunstein for his comments andadvice in the preparation of this paper.

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