Objective: The photoplethysmographic wave is displayed by most pulse oximeters. It may be used as anon-invasive alternative to invasive arterial blood pressure trace analysis for continuous haemodynamic monitoring in selected situations. Patients and setting: Four cardiac patients treated in atertiary neonatal-paediatric intensive care unit. Measurements: Simultaneous monitoring of the photoplethysmographic wave, ECG, and invasive blood pressure. Results and conclusions: Photoplethysmography allows for monitoring pulse rate in patients with (possible) heart rate/pulse rate dissociation (pacemaker dependency, pulsatile ventricular assist device); monitoring sudden changes in heart beat volume, which are unrelated to respiration (pulseless electrical activity, pulsus alternans); and monitoring respiratory-dependent fluctuations of the plethysmographic wave (heart failure, hypovolaemia, asthma, upper airway obstruction, pericardial effusion). Deterioration, slowly evolving over time, may be detected by this metho

Balmer, Christian

Frey, Bernhard

Waldvogel, Katharina

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Intensive Care Med (2008) 34:578–582DOI 10.1007/s00134-007-0951-1 CASE DISCUSSIONBernhard FreyKatharina WaldvogelChristian BalmerClinical applicationsof photoplethysmographyin paediatric intensive careReceived: 6 July 2007Accepted: 13 November 2007Published online: 11 December 2007© Springer-Verlag 2007Abstract Objective: The photo-plethysmographic wave is displayedby most pulse oximeters. It may beused as a non-invasive alternative toinvasive arterial blood pressure traceanalysis for continuous haemodynam-ic monitoring in selected situations.Patients and setting: Four cardiacpatients treated in a tertiary neonatal-paediatric intensive care unit. Meas-urements: Simultaneous monitoringof the photoplethysmographic wave,ECG, and invasive blood pressure.Results and conclusions: Photo-plethysmography allows for monitor-ing pulse rate in patients with (possi-ble) heart rate/pulse rate dissociation(pacemaker dependency, pulsatileventricular assist device); monitoringsudden changes in heart beat volume,which are unrelated to respiration(pulseless electrical activity, pulsusalternans); and monitoring respira-tory-dependent fluctuations of theplethysmographic wave (heart failure,hypovolaemia, asthma, upper airwayobstruction, pericardial effusion).Deterioration, slowly evolving overtime, may be detected by this method.Keywords Paediatrics · Pulse oxime-try · Photoplethysmography · Cardio-vascular monitoringIntroductionPulse oximetry has become one of themost valuable monitoring techniquesin intensive care for continuous evalu-ation of arterial haemoglobin oxygensaturation. In addition to the digitalread-out of oxygen saturation, mostpulse oximeters display a plethysmo-graphic waveform, which can helpclinicians to distinguish an artefac-tual signal from the true signal [1];however, there may be further clinicalapplications of the plethysmographicwaveform. Photoplethysmographydetects changes in blood volume inthe tissue under where the probe isapplied. The displayed pulse wavesarise from heart-beat-dependent vol-ume changes in the terminal arterialbed. The slower respiratory waves arecaused by blood volume changes inthe venous bed. These characteristicsmake the plethysmographic wavea useful tool for non-invasive haemo-dynamic monitoring in some clinicalsettings in the paediatric intensivecare unit.MethodsWe present examples recorded fromchildren we treated in our tertiaryneonatal and paediatric intensive careunit. A Solar 8000M Modular Pa-tient Monitor was used (GE MedicalSystems, Freiburg, Germany) withbuilt-in Nellcor N-100 pulse oximeter(Nellcor, Pleasanton, Calif.).Monitoring pulse rateCase 1A 16-year-old boy with severe cardio-myopathy was put on a pulsatileventricular assist device (BerlinHeart, Berlin, Germany). He wasnon-invasively monitored by pulseoximetry and ECG. While the plethys-mographic wave shows the ven-tricular-assist device frequency of60/min, the ECG shows the electricalactivity of the own heart (atrio-ven-tricular pacing, 129/min; Fig. 1).Similarly, in the cardiac pace-maker-dependent child, ECG mon-itoring alone may not trigger analarm in the case of cardiac arrest.In the presence of cardiac arrest,the ECG monitor may continue tocount pacemaker artefact. Pulse-ratemonitoring by pulse oximetry isalso useful in arrhythmias such asbigeminus. Analysis of the plethys-mographic wave may be helpfulin distinguishing arrhythmia fromartefact on the ECG and may giveclues to the haemodynamic relevanceof the arrhythmia.The pulse-rate display of thepulse oximeter is useful for two mainreasons: firstly, the pulse-rate valueshould correlate with the measuredheart rate, before the saturationreading is accepted. Secondly, re-lated to cardiac output, pulse rateis relevant and not heart-/ECG rate;therefore, whenever dissociationbetween heart-/ECG rate and pulserate is anticipated, as in case 1 or ina pacemaker-dependent child who isat risk of respiratory failure or loss ofpacemaker capture, plethysmographybecomes an important monitoringtool [2].Monitoring respiratory-dependentfluctuations of the plethysmographicwaveCase 2A 5-month-old boy with junctionalectopic tachycardia after heart surgery(tetralogy of Fallot repair) was firsttreated with cooling and amiodarone.Heart rate decreased from 210 to157/min. Analysis of the plethysmo-graphic wave revealed pronounced(ventilation-dependent) fluctuations(Fig. 2a). The ventilation-relatedsystolic arterial pressure fluctuations(pulsus paradoxus) were 10 mmHg.With sequential atrio-ventricularpacing (176/min) and unchangedventilation parameters (peak inspira-579Fig. 1 Electrocardiogram andplethysmographic wave (Pleth)of case 1. The patient’s heart rateis 129/min on the ECG tracing(atrio-ventricular pacing), whilethe completely dissociated pulsegenerated by the mechanicalassist device is seen at 60/mintory pressure 24 cm H2O, PEEP4 cm H2O, frequency 34/min, muscleparalysis), the plethysmographicfluctuations were less pronounced(Fig. 2b, 5 min after the start ofpacing). The systolic arterial pressurefluctuations decreased to 3 mmHg.The mean arterial blood pressureremained unchanged. No volumewas infused. Cardiac output was notmeasured.We assume that restoration ofAV synchrony by pacing resulted inimproved cardiac output and that thedecrease in respiratory-dependentblood pressure fluctuations wasrelated to the improved cardiacperformance.In cardiac patients with stablerespiratory state, variations inrespiratory-dependent blood pres-sure fluctuations (pulsus paradoxus)may indicate variations in cardiacperformance [3]. In mechanical ven-tilation, the cyclic, constant intra-thoracic pressure variations inducecyclic changes of arterial systolicblood pressure (reversed pulsusparadoxus) which are related tocyclic changes in left ventricularstroke volume [4]. In mechanic-ally ventilated patients, a strongcorrelation and a good agreementbetween respiratory variation in ar-terial pulse pressure and respiratoryvariation in pulse oximetry plethys-mographic waveform amplitude hasbeen shown [5]. Lacking invasivearterial blood pressure monitoringor in the case of technical problems(e.g. damped wave), analysis of thephotoplethysmographic wave mayfacilitate demonstrating success-ful therapy or titrating therapy, asshown in case 2 and recently demon-strated for volume dependency inadult patients [6]. Pulsus paradoxusdue to heart failure in paroxysmalsupraventricular tachycardia (SVT)is also detectable by pulse oxime-try [7]. High respiratory-dependentfluctuations of the plethysmographicwave in an infant with SVT al-most completely disappeared af-ter conversion to a regular sinusrhythm [7].Increasing respiratory-dependentfluctuations of the plethysmographicwave (pulsus paradoxus) may alertthe clinician in other situationstoo: status asthmaticus [8]; upperairway obstruction [9]; and peri-cardial effusion [10]. In childrenat risk of pericardial tamponade,increasing respiratory-dependentfluctuations of the plethysmo-graphic wave may be an earlysign of aggravation, before appear-ance of the classical signs suchas tachycardia, hypotension anddistension of the external jugularvein [10].There is scarce informationregarding the physiological prin-ciples underlying these clinicalobservations. Two types of photo-plethysmographic waves can berecognized: the pulse waves andthe slower respiratory waves. Therespiratory waves are caused byblood volume changes in the venousbed. Respiration-dependent intratho-racic pressure changes produce vari-ations in venous return to the rightside of the heart and thus in bloodvolume mainly in the venous bed,since the venous compliance is tentimes greater than the arterial [11].These respiratory-dependent vol-ume changes of the venous bedare detected by the amplitude ofthe plethysmographic respiratorywave. The amplitude changes of580the plethysmographic pulse waveare significantly influenced by thedistensibility of the arterial wall,which is controlled by the auto-nomic nervous system [11]. Theamplitude of the plethysmographicrespiratory wave seems to reflectvariation in intrathoracic pressuremore reliably [8]. In non-intubatedchildren with or without respiratorydisorders, it has been shown that thephotoplethysmographic fluctuationsof the upper peak (mm) correlatedwith invasively measured pulsusparadoxus (mmHg; r = 0.85) [8].The degree of pulsus paradoxusreflects the severity of the underly-ing disorder. In patients receivingmechanical ventilation, reversedpulsus paradoxus can be monitoredFig. 2 Electrocardiogram,invasive arterial pressure andplethysmographic wave (Pleth)of case 2. This is a patient withpost-operative junctional ectopictachycardia who has variableAV association (without andwith pacing) resulting in pro-nounced and less pronouncedplethysmographic and arterialpressure fluctuations.a Pronounced plethysmographicfluctuations with junctionalrhythm (systolic arterial pres-sure fluctuations 10 mmHg; notobvious due to the large scale).b Less pronounced plethysmo-graphic fluctuations on atrio-ventricular sequential pacing(arterial pressure fluctuations3 mmHg)(inspiratory increase in systolic bloodpressure) [12].Monitoring sudden changes in heartbeat volume, which are unrelated torespirationCase 3A 9-year-old boy with arrhythmiasrelated to long QT syndrome wasmonitored in the ICU. The record-ing in Fig. 3 shows an episode ofventricular tachycardia (“torsades depointe”), induced by an electricalimpulse on the T wave via a newlyimplanted cardioverter/defibrillator(ICD) to test the device. Duringthe ventricular tachycardia arterialpressure and plethysmographic waveswere flat. The CVP was increased.Case 4This is the same patient as case 1,before Berlin Heart implantation.He was spontaneously breathingand treated with dobutamine, capto-pril and diuretics (ejection fraction30%, central venous oxygen satu-ration 54%). The photoplethysmo-graphic wave showed diminutionsof the amplitude on alternate beats(Fig. 4).In case 3, photoplethysmographicwaveform duplicates arterial pressurewaveform morphological abnormal-ities. Activation of the “plethysmo-581Fig. 3 Electrocardiogram,plethysmographic wave (Pleth),invasive arterial pressure andcentral venous pressure (CVP)of case 3. During ventriculartachycardia, the blood pressureand pleth tracings are flat. Thisexample shows an invasivelymonitored patient with a dis-order that typically is seen inpatients without invasivemonitoringFig. 4 Electrocardiogram and plethysmographic wave (Pleth) of case 4: a spontaneouslybreathing patient with severe dilated cardiomyopathy. The pleth wave shows diminutions ofthe amplitude on alternate beats (pulsus alternans)graph non-pulsatile” alarm may bethe first alert to the occurrence ofpulseless electrical activity in a non-invasively monitored patient [2].Pulsus alternans (case 4) is due toan alternating strength of contrac-tion from one beat to the next (notattributable to bigeminal rhythms)seen in more severe forms of cardiacfailure (e.g. cardiomyopathies, aorticstenosis). Plethysmography clearlydemonstrates this phenomenon(case 4) [13]. Early detection of thisabnormality may be useful in guidingdiagnosis and treatment. The patientwith cardiomyopathy and subsequentBerlin Heart support (cases 1 and 4)clearly shows the benefits of photo-plethysmography. Firstly, when thepatient had not yet an arterial line,the pulse oximeter tracing pointedto the severity of the myocardialdysfunction and more invasive moni-toring was started. Subsequently,after the mechanical support had beenimplanted, invasive arterial monitor-ing was stopped and non-invasivemonitoring by plethysmographyresumed.582LimitationsAlthough we previously showed thatphotoplethysmography can be usedquantitatively for estimation of thedegree of pulsus paradoxus [8], thecases presented here clearly showqualitative applications of photo-plethysmography. There are numer-ous manufacturers for pulse oximetersand photoplethysmographic probes;thus, the photoplethysmographiccharacteristics from each modeland/or different manufacturers maydiffer. This applies to movementartefacts, ambient lighting, indi-vidual tissue characteristics andauto-gain features. Pulse oximeterswith auto-gain features are less usefulin depicting a persisting reductionin perfusion, but they remain validin representing short cyclic varia-tions in pulse volume, such as inpulsus paradoxus [8, 13]. Further-more, in situations of peripheralvascular constriction (low cardiacoutput, catecholamine therapy andhypothermia) the probe (especiallyif in perfusion mode) may not workappropriately [1]; however, the quali-tative features shown in this studymay be present even in these circum-stances. In fact, some of the presentedpatients were in low cardiac outputand/or had catecholamine therapy. Inthe present case series, repeatabilitywas not tested; however, repeatabilitywas shown at least for airway ob-struction [9], pericardial effusion [10]and pulsus paradoxus in spontan-eously breathing [8] and ventilatedpatients [5]. Most importantly, thiselectronic device should not replacecareful clinical monitoring, such ascapillary refill, skin temperature andECHO, and it may only be used asan adjunct to complete the clinicalpicture. Finally, this technique is butanother electronic form of “feelingthe pulse”. So far, this tool is with-outproven significance with regard tomonitoring adverse events. Prospec-tive investigations should be per-formed to identify how many ofall patients can be monitored, howmany artefacts do occur and whethertherapy changes according to thereadings.ConclusionThe photoplethysmographic wavewhich is displayed by most pulseoximeters may be used for addi-tional haemodynamic informationin some selected situations when anarterial blood pressure monitoringis not available. The advantagesof this method are its widespreaduse, non-invasiveness and continu-ity. Haemodynamic deterioration,whether suddenly occurring or slowlyevolving over time, may be detectedby this method. A problem with usingphotoplethysmography is movementartefact. There is only minimal ref-erence to photoplethysmographymonitoring, except for case series forassessment of pulsus paradoxus inobstructive airway disease [8, 9].References1. Jubran A (2004) Pulse oximetry.Intensive Care Med 30:2017–20202. Brownlee JR, Serwer GA, Dick M,Bauld T, Rosenthal A (1989)Failure of electrocardiographicmonitoring to detect cardiac ar-rest in patients with pacemakers.Am J Dis Child 143:105–1073. Pizov R, Ya’ari Y, Perel A (1989) Thearterial pressure waveform during acuteventricular failure and synchronizedexternal chest compression. AnesthAnalg 68:150–1564. Michard F, Teboul JL (2000) Usingheart-lung interactions to assess fluidresponsiveness during mechanicalventilation. Crit Care 4:282–2895. Cannesson M, Besnard C, Durand PG,Bohé J, Jacques D (2005) Relationbetween respiratory variations inpulse oximetry plethysmographicwaveform amplitude and arterialpulse pressure in ventilated patients.Critical Care 9:R562–R5686. Feissel M, Teboul JL, Merlani P,Badie J, Faller JP, Bendjelid K (2007)Plethysmographic dynamic indicespredict fluid responsiveness in septicventilated patients. Intensive Care MedDOI 10.1007/s00134-007-0602-67. Frey B (1999) Pulsus paradoxus in-dicating heart failure in paroxysmalsupraventricular tachycardia: easydetection by pulse oximetry. IntensiveCare Med 25:333–3348. Frey B, Butt W (1998) Pulse oximetryfor assessment of pulsus paradoxus:a clinical study in children. IntensiveCare Med 24:242–2469. Arnold DH, Spiro DM, Desmond RA,Hagood JS (2005) Estimation ofairway obstruction using oxime-ter plethysmograph waveform data.Resp Res 6:6510. Tamburro RF, Ring JC, Womback K(2002) Detection of pulsus paradoxusassociated with large pericardialeffusions in pediatric patients byanalysis of pulse-oximetry waveform.Pediatrics 109:673–67711. Dorlas JC, Nijboer JA (1985) Pho-toelectric plethysmography asa monitoring device in anaesthesia.Br J Anaesth 57:524–53012. Jardin F, Farcot JC, Gueret P, Prost JF,Ozier Y, Bourdarias JP (1983) Cyclicchanges in arterial pulse during respira-tory support. Circulation 68:266–27413. Dennis MJ (2000) Plethysmography:the new wave in haemodynamicmonitoring – a review of clinicalapplications. Aust Crit Care 13:14–20B. Frey () · K. WaldvogelUniversity Children’s Hospital, Departmentof Intensive Care and Neonatology,8032 Zurich, Switzerlande-mail: Bernhard.Frey@kispi.uzh.chTel.: +41-44-2667359Fax: +41-44-2667168C. BalmerUniversity Children’s Hospital, Departmentof Cardiology,8032 Zurich, Switzerland

Clinical applications of photoplethysmography in paediatric intensive care

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Clinical applications of photoplethysmography in paediatric intensive care

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