trans cutaneous carbon dioxide and oxygen monitoring in the adult patient

Transcutaneous technology for thenoninvasive monitoring of oxygenand carbon dioxide has been usedfor about 40 years. The coveredpolarographic blood gas electrodefor oxygen was modified fortranscutaneous use by EVANS andNAYLOR [1] in 1967. This electrodedid not heat the underying skin andtherefore measured the oxygen levelat normal skin surface temperature.Their work showed that the level ofoxygen diffusing from the dermalcapillaries to the skin surface ismainly governed by skin bloodflow and temperature. This led tothe development of transcutaneouselectrodes which incorporated athermostatically controlled heatingelement to maximise local bloodflow. A good relationship betweentranscutaneous oxygen tension

(Ptc,O2) and arterial oxygen tension(Pa,O2) was demonstrated inneonates and this led to the use ofcontinuous noninvasive Ptc,O2

monitoring in neonatal intensivecare units [2]. It was initiallybelieved that Ptc,O2 measurementswould not be satisfactory in adultsdue to their thicker epidermis, butsubsequent studies have shown thatthis technology may work just aswell for older children and adults[3, 4]. The transcutaneous electrodefor the assessment of carbondioxide consists of a Stow–Severinghaus glass electrochemicalsensor that has been modified fortranscutaneous use by theincorporation of a thermostaticallycontrolled heater unit as in thePtc,O2 electrode [5]. Closecorrelations between

TRANSCUTANEOUS CARBONDIOXIDE AND OXYGENMONITORING IN THE ADULTPATIENTR. Carter

CorrespondenceR. Carter

Dept of Respiratory MedicineRoyal Infirmary

GlasgowG31 2ER

UK

E-mail: [email protected]

TRANSCUTANEOUS CARBON DIOXIDE AND OXYGEN MONITORING IN THE ADULT PATIENT07

102 THE BUYERS’ GUIDE TO RESPIRATORY CARE PRODUCTS

Amy Goodchildistockphoto

BG-07 NI Blood Gases 6/8/07 20:47 02

transcutaneous carbon dioxidetension (Ptc,CO2) and arterial carbondioxide tension (Pa,CO2) have againbeen demonstrated in adults as wellas in neonates [6, 7].

Transcutaneous measurements ofoxygen and carbon dioxide arebased on the principle that a heatingelement in the electrode elevates thetemperature of the underlyingtissues. This increases the capillaryblood flow and the partial pressureof oxygen and carbon dioxide, andmakes the skin permeable to gasdiffusion (fig. 1). It must beremembered that the electrode ismeasuring the gas tensions of theunderlying tissue and not thearterial gas tension. Whenhaemodynamic conditions arestable, the transcutaneousmeasurements correlate well witharterial values but are not identical.The actual level of transcutaneousoxygen reflects the relationshipbetween the increase in partialpressure in the capillary blood dueto heating, the level of skin bloodflow and the metabolic oxygenconsumption of the skin. In spite ofthese physiological factors, whenblood flow is normal,transcutaneous oxygen values canreliably reflect arterial values. In thecase of Ptc,CO2, the elevatedtemperature at which thetranscutaneous electrode operates inorder to increase skin permeabilitywill also raise skin metabolism andlead to an increase in CO2

production. The measured valueswill, therefore, be significantlyhigher than arterial values at 37oC.The transcutaneous values can betemperature corrected, thusenabling a readout of valuescomparable to those at the normalbody temperature. These willdeviate by a small metaboliccontribution from the carbondioxide production in the epidermis.Transcutaneous monitoring ofcarbon dioxide tension (PCO2) hasbeen shown to be more reliable thanthe transcutaneous measurement ofoxygen due to the greater diffusioncapacity of carbon dioxide throughthe skin.

The more recent development intranscutaneous technology has beenthe introduction of a solid-statecombined Ptc, O2/Ptc, CO2 electrodewith the glass section of the Ptc, CO2

electrode being strengthened byincorporation of ceramic material,making it much more robust andless liable to damage [8].

Calibration methods

The polarographic method ofmeasuring transcutaneous oxygenrequires only a two-pointcalibration procedure as the signaloutput from a Clark cell is virtuallylinear over the physiological range.For the lower point calibration, anelectrical zero will suffice, beingequivalent to zero PCO2. Theconventional calibration of theupper point usually uses a dry gasof suitable composition or room air.Calibration in this mannergenerally leads to underestimationof P,O2 compared with arterialvalues. For the transcutaneouscarbon dioxide electrode, thestandard method of calibrationinvolves the use of two known gasmixtures, commonly 5 and 10%CO2. This method of calibrationproduces results that exceed thetrue arterial Pa, CO2 by an amountlargely determined by electrode

TRANSCUTANEOUS CARBON DIOXIDE AND OXYGEN MONITORING IN THE ADULT PATIENT

THE BUYERS’ GUIDE TO RESPIRATORY CARE PRODUCTS 103

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Figure 1. A transcutaneous gas tension measurement electrode.

BG-07 NI Blood Gases 6/8/07 20:47 Page 103

temperature. Due to the potentialerrors that can arise from the gascalibration method, it is alsopossible to calibrate thetranscutaneous oxygen and carbondioxide upper points by using theindependently measured Pa,O2 andPa,CO2 in the subject’s own arterialor arterialised ear lobe capillaryblood sample. With this method,the electrode is attached to the skinand a stable provisional Ptc,O2 andPtc,CO2 are obtained. This warm-upperiod is one disadvantage oftranscutaneous monitoring as it cantake some time (usually 10–20 min)for the electrode to reach itsoptimal working conditions. Anarterial sample or arterialised earlobe capillary sample is obtainedand the Ptc,O2 and Ptc,CO2 signalgains can then be adjusted to thevalues obtained from the directlymeasured blood sample. This “invivo” method of calibration has theadvantage that all of theunpredictable “skin factors”contributing to the differencesbetween transcutaneous andarterial values remain relativelyconstant, provided that a constanttemperature and heat field can beestablished in the skin. The twocalibration methods have beencompared in several studies andhave shown that thetranscutaneous values can providea more accurate estimation of truearterial values if the in vivocalibration method is used [9, 10].In the intensive care unit, thismethod offers no additionalproblems if an arterial cannula isalready in situ. This is generally notthe case in patients undergoingphysiological testing and it mightbe suggested that arterial or earlobe capillary sampling isunjustified in these circumstances,however properly performed, asingle arterial stab or ear lobecapillary sampling can be a trouble-free procedure.

Response time

The response time to a square wavechange in PO2 in the gas phase is

rapid and equilibrium is usuallyobtained within 30 s. Previously,Ptc,CO2 electrodes were slower torespond than Ptc,O2 electrodes butwith current systems their responsetime is almost as fast. Modernelectrodes are therefore capable ofresponding faithfully to virtuallyany physiological change that islikely to occur. In contrast, the invivo response times depend onmany physiological variables thatare not necessarily constant. The90% response time for a change innormal subjects from normoxic tohypoxic conditions has been shownto be ~40 s for Ptc,O2 and ~60 s forPtc,CO2 at the highest electrodetemperature of 45oC [10]. The invivo response time increases withreducing electrode temperature [11].

Site selection

The absolute value of Ptc,O2 isaffected by skin thickness andcapillary density. It is thereforeimportant to place the electrode at asite of high capillary density andminimal thickness for optimaltranscutaneous measurements. Thispresents no problem in thenewborn, in whom these conditionsare usually fulfilled. In adults, thereis greater variation from site to siteand the suggested locations foroptimal transcutaneousmeasurements are the forearm,chest or abdomen.

Combined Ptc,CO2 and pulseoximetry

In adults, as mentioned previously,the transcutaneous partial pressureof oxygen depends heavily on localskin perfusion and may not reliablyreflect true Pa,O2 unless an “in vivo”calibration has been performed.This has led to the development ofa combined sensor for themeasurement of bothtranscutaneous CO2 and pulseoximetric saturation (Sp,O2) ratherthan Ptc,O2. This electrode containsan electrochemical electrode (forPtc,CO2), a light emitter/sensor (for

Sp,O2 measurement) and a heatingelement (to increase localperfusion). The small size of thesensor allows convenient placementon the earlobe. Calibration of thePtc,CO2 sensor is the same as above.This sensor has been shown toaccurately reflect directly measuredPa,CO2 and arterial oxygensaturation (Sa,O2) in adults andchildren undergoing generalanaesthesia, to reflect ventilationand oxygenation [12, 13]. Inaddition, this combined sensor hasbeen shown to accurately monitorSa,O2 and Pa,CO2 in critically illpatients and patients with sleepapnoea using an electrodetemperature of 42oC [14]. Theauthors suggested that owing to itsability to assess both ventilationand oxygenation noninvasively, inaddition to pulse rate by a singletranscutaneous sensor, thistechnique is a convenient andvaluable tool for respiratorymonitoring with potentialapplications in critical care,anaesthesia and sleep medicine.This sensor has also been validatedin the care of neonates [15, 16].

Applications

Peripheral vascular disease

In patients with peripheral vasculardisease, transcutaneous oxygenprovides a useful supplement whenevaluating the severity of theillness. Impairment of blood flow inthe region next to the electrode maylead to a considerableunderestimate of the true Pa,O2. Thisproperty has been utilised in theassessment of local blood flow andin studies of lower limb ischaemia.Ischaemia caused by peripheralvascular disease accounts for themajority of lower limb amputations.Although the standard practice is toassess limb perfusion throughphysical examination and clinicaljudgement, the development ofquantitative measurements ofperfusion is important as perfusiondetermines the degree andprogression of the pathological




process that can lead to amputation.In order to establish the idealamputation level, a perfusion-basedmethodology that can accuratelydetermine the boundaries betweenthose tissues that cannot potentiallyheal and those that can healuneventfully would be anadvantage. As local blood flow isknown to be a limiting factor inachieving equilibrium betweenPa,O2 and Ptc,O2, this phenomenonmay be used to estimate the localperfusion deficit by measuring thePtc,O2 reached after enhancing bloodflow by local heating with a seriesof transcutaneous electrodes indifferent leg positions [17]. Thisprocedure often makes it possible topredict whether amputation isneeded. A reference level of 2.66 kPa(20 mmHg) has been suggested asbeing suitable for evaluation of theamputation level [18]. In bothvenous and arterial diseases, Ptc,O2

can be used to evaluate the effect oftherapeutic interventions [19].

Cardiopulmonary exercise testing

Accurate and reliablemeasurements of gas exchange areimperative during cardiopulmonaryexercise testing. The slow responsecharacteristics of the combinedtranscutaneous electrode have beenviewed as a major disadvantagewhen compared with other types ofnoninvasive assessment of gasexchange during exercise testing. Ithas been shown however that the invivo calibration method is able toproduce a close agreement betweenPtc,O2 and Pa,O2 at all stages of anexercise test in both patients andnormal subjects. The use of thehighest electrode temperature andsubsequent increase in responsetime makes it possible to monitorany physiological changes in bloodgases that occur [4, 10]. There wasno morbidity associated with theuse of the transcutaneous electrodeheated to 45 oC. It has also beenshown that using a gradualincremental exercise protocol (2-minincrements), to allow for the latencyin the response time of the system,it is possible to derive accurate

parameters of gas exchange(alveolar–arterial oxygen gradientand dead space/tidal volume ratio)during exercise testing [20]. Thistechnique allows the assessment ofthe contribution ofventilation/perfusion inequality tobreathlessness on exertion inpatients, provided an in vivocalibration is performed. Thetechnique is particularly valuable inpatients undergoing repeat exercisetests as it circumvents the need forarterial cannulation. The use oftranscutaneous monitoring to assessgas exchange during exercise hasbeen used in a number of patientgroups, including those withcardiac failure being assessed for orfollowed up after cardiactransplantation [21–23].

Sleep disorders

Many neuromuscular andcardiorespiratory disorders arecomplicated by sleep disturbances.Apnoeas and sudden desaturationswith hypoxia are a feature ofpatients with sleep apnoea, but theresponse of the transcutaneousoxygen electrode is too slow toaccurately assess the number ofhypoxic dips and in this case pulseoximetry is usually the first choice ofassessment [24]. When using pulseoximetry, the use of an appropriatesignal-averaging time is importantsince, once again, the use of too longan averaging time will significantlyunderestimate the number ofhypoxic dips [25]. Continuousmonitoring of Ptc,CO2 during sleepmay be considered if nocturnal CO2

retention is to be documented.Transcutaneous monitoring of PCO2

has been a useful measurement inpatients with respiratory failure dueto COPD [26, 27]. The main problemwith the use of transcutaneousmonitoring is the need to change thesite of the electrode to preventthermal skin trauma if an electrodetemperature >43oC is employed. It ispossible to obtain effective Ptc,CO2 atlower temperatures (42oC) giving asite time of up to 8 h. Thedevelopment of the combinedPtc,CO2/Sp,O2 using an electrode

temperature of 42oC, which does notadversely affect the accuracy ordynamic response characteristics ofthe pulse oximeter [14], has thepotential to assess both ventilation interms of transcutaneous CO2 andrapid fluctuations in Sp,O2 in patientswith sleep-disordered breathing.

Respiratory support

Noninvasive ventilation

Domiciliary noninvasive ventilation(NIV) and tracheotomy-mediatedmechanical ventilation are effectiveprocedures for managing severehypercapnic chronic respiratorydisease. It is recommended thatassessing diurnal gas exchange isessential in order to confirm theefficacy of ventilation at initiationand during follow-up. In most casesthe daytime blood gases will beabnormal with an elevated Pa,CO2

and low Pa,O2 but in somesymptomatic patients the daytimeblood gases may be normal.Overnight studies frequently revealfar greater abnormality asrespiratory impedance rises andventilator drive falls during sleep.Noninvasive arterial oxygenation isroutinely and satisfactorilymonitored with transcutaneouspulse oximeters. Noninvasive Pa,CO2

monitoring, however, is morecomplex and still requires serialarterial blood sampling. NIV is aleak ventilation; end-tidal CO2

measurements are subject to largevariability resulting in a reduction inthe correlation with Pa,CO2. Interesthas centred on the measurement ofPtc,CO2 if rapid tracking of transientfluctuations of Pa,CO2 is not essential.The use of the combinedPtc,CO2/Sp,O2 sensor has beenvalidated against measurements onarterial blood gas samplesrepeatedly drawn from indwellingarterial lines [14] and been shown toaccurately monitor directlymeasured Pa,CO2 and Sa,O2, and theirchanges in critically ill adult patients[28]. This technology has beenshown to be useful in the initiationof noninvasive ventilation andtitrating of ventilator settings for



07


the treatment of chronic respiratoryfailure [29] as some of these patientsare sensitive to supplemental oxygenand readily become hypercapnic ifnot monitored appropriately.Overnight studies to assess for NIVare also particularly important inthose patients with chest wall orneuromuscular disease [30].

If NIV is to be introduced during anacute episode of ventilator failure,continuous monitoring of Ptc,CO2 toallow timely decision making is evenmore important. To determinewhether the treatment is working itis necessary to record the CO2.Arterial measurements cannot bemade continuously, and if additionaloxygen is used this will invalidateSp,O2 as a surrogate measure ofventilation. If the Ptc,CO2 does notfall with NIV, the patient mayrequire intubation and ventilation.

Weaning from invasive ventilation

Whenever changes are made toventilator support it is important tomeasure the effect on arterial bloodgases. This is especially importantduring weaning, when ventilatorsupport is being reduced. Usingcontinuous noninvasivemeasurements of Ptc,CO2 and Sp,O2

will be less disturbing to the patientthan repeated arterial stabs orsampling from indwelling lines. Atthe time of extubation changes inblood chemistry may occur quicklyand the noninvasive monitoringwith Sp,O2 and Ptc,CO2 will give anearly indication if the patient’s ownventilator effort is inadequate.Continuous monitoring of thesevariables may also suggest that theinitiation of NIV may need to beconsidered.

Titrating long-term oxygen therapy

Long-term oxygen therapy (LTOT) ismost frequently prescribed forpatients with COPD. Once a patienthas been identified as likely tobenefit from LTOT, the oxygen levelsare titrated up to a maximum flowrate which corrects the hypoxia butwithout worsening hypercapnia to a

level which is symptomatic or whichmay be considered to put the patientat risk of rapid deterioration whenthey are given additional oxygen. Ithas been suggested that continuousnoninvasive monitoring of Sp,O2 andPtc,CO2 during the titration may helpto identify the optimum flow rate atwhich point formal assessment ofarterial blood gases can beperformed to ensure that thehypoxia has been corrected and thathypercapnia has not been induced.The use of transcutaneousmonitoring during the titrationreduces the number of arterial orarterialised ear lobe capillarysamples that need to be obtained. Itmay also be possible to repeat thisprocess during sleep, whenventilation is at its most vulnerable.If in this case the transcutaneousPtc,CO2 is further elevated, then NIVmay be a more appropriatetreatment.

Adult anaesthesia

During general anaesthesia, post-operative recovery and critical caretreatment, the monitoring ofoxygenation and ventilation areimportant. As pulse oximetry onlyestimates arterial oxygen saturation,periodic blood sampling would stillbe necessary to fully determine thepatient’s ventilation status by themeasurement of Pa,CO2. It has beenshown that during generalanaesthesia [31], a combinedPtc,CO2/Sp,O2 ear sensor, producedtranscutaneous values of CO2 whichdid not differ significantly fromdirectly measure Pa,CO2. The authorssuggested that the combined sensorproved to be a reliable tool forcontinuous noninvasive monitoringof oxygenation and ventilation.

Overall, the range of devices fortranscutaneous assessment ofoxygen and carbon dioxide havebeen shown to give a reliableindication of arterial levels especiallyif an in vivo calibration is performed.They are able to provide acontinuous noninvasive assessmentof oxygenation and ventilation in anumber of clinical situations. ■






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1. Evans NTS, Naylor PFD. The systemic oxygen supply to the surface of human skin. Respir Physiol 1967: 3: 21–37.

2. Huch R, Huch A, Albani M, et al. Transcutaneous PO2 monitoring in routine management of infants and children with cardiorespiratoryproblems. Pediatrics 1976; 57: 681–690.

3. Hutchison DCS, Rocca G, Honeybourne D. Estimation of arterial oxygen tension in adult subjects using transcutaneous electrode.Thorax 1981; 36: 473–477.

4. Hughes JA, Gray BJ, Hutchison DCS. Changes in transcutaneous oxygen tension during exercise in pulmonary emphysema. Thorax1984; 39: 424–431.

5. Severinghaus JW, Stafford M, Bradley AF. TcPCO2 electrode design, calibration and temperature gradient problems. Acta AnaesthesiolScand Suppl 1978; 68: 118–122.

6. Goldman MD, Gribbin HR, Martin RJ, Transcutaneous pCO2 in adults. Anaesthesia 1982; 37: 944–946.

7. Binder N, Atherton H, Thorkelsson T, Hoath SB. Measurement of transcutaneous carbon dioxide in infants during the first two weeks oflife. Am J Perinatol 1994; 11: 237–241.

8. Larsen J, Linnet N, Vesterger P. Transcutaneous devices for the measurement of PO2 and PCO2. State of the art, especiallyemphasizing a PCO2 sensor based on a solid state gas pH sensor. Am Biol Clin (Paris) 1993, 50: 899–902.

9. Gray BJ, Heaton RW, Henderson A, Hutchison DCS. In vivo calibration of a transcutaneous oxygen electrode in adult patients. AdvExp Med Biol 1987; 200: 75–77.

10. Sridhar MK, Carter R, Moran F, Banham SW. Use of a combined oxygen and carbon dioxide transcutaneous electrode in theestimation of gas exchange during exercise. Thorax 1993; 48: 643–647.

11. Nishiyama T, Nakamura S, Yamashita K. The effects of the electrode temperature of a new monitor, TCM4, on the measurement oftranscutaneous oxygen and carbon dioxide tension. J Anesth 2006; 20: 331–334.

12. Eberhard P, Gisiger PA, Gardaz JP, Spahn DR. Combining transcutaneous blood gas measurement and pulse oximetry. Anesth Analg2002; 94: S86–S80.

13. Dullenkopf A, Bernardo S, Berger F, Fasnacht M, Gerber AC, Weiss M. Evaluation of a new combined SpO2/PtcCO2 sensor inanaesthetised paediatric patients. Paediatr Anaesth 2003; 13: 1–8.

14. Senn O, Clarenbach CF, Kaplan V, Maggiorini M, Bloch KE. Monitoring carbon dioxide tension and arterial oxygen saturation by asingle earlobe sensor in patients with critical illness or sleep apnea. Chest 2005; 128: 1291–1296.

15. Bernet-Buettiker V, Ugarte MJ, Frey B, Hug MI, Baenziger O, Weiss M. Evaluation of a new combined transcutaneous measurementof PCO2/pulse oximetry oxygen saturation ear sensor in newborn patients. Pediatrics 2005; 115: 64–68.

16. Parker SM, Gibson GJ. Evaluation of a transcutaneous carbon dioxide monitor (“TOSCA”) in adult patients in routine practice. RespirMed 2007; 101: 261–264.

17. Figoni SF, Scremin OU, Krunkel CF. Pre-amputation evaluation of limb perfusion with laser Doppler imaging and transcutaneousgases. JRRD 2006; 43:891–904.

18. Misuri A, Lucertini G, Nanni A, Viacava A, Belardi P. Predictive value of transcutaneous oximetry for selection of the amputation level.J Cardiovasc Surg 2000; 41: 83–87.

19. Melillo E, Nuti M, Pedrinelli R, Buttitta F, Balbarini A. Is transcutaneous oxygen and carbon dioxide monitoring indispensible in shortand long term therapeutic management of non-reconstructable lower critical limb ischaemia? Minerva Cardioangiol 2006; 54:481–498.

20. Carter R, Banham SW. Use of transcutaneous oxygen and carbon dioxide tensions for assessing indices of gas exchange duringexercise testing. Respir Med 2000; 94: 350–355.

21. Tweddel A, Carter R, Banham SW, Hutton I. Breathlessness in microvascular angina. Respir Med 1994; 88: 731–736.

22. Al-Rawas OA, Carter R, Richens D, et al. Ventilatory and gas exchange abnormalities on exercise in chronic heart failure. Eur RespirJ 1995; 8: 2022–2028.

23. Carter R, Al-Rawas OA, Stevenson A, Mcdonagh T, Stevenson RD. Exercise responses following heart transplantation: 5 year follow-up. Scott Med J 2006; 51: 6–13.

24. Wiltshire N, Kendrick AH, Catterall JR. Comparison of two pulse oximeters for sleep studies in the home and in the laboratory. EurRespir J 1995; 8: Suppl 19, 149s.

25. Kendrick AH, Wiltshire N, Catterall JR. Effect of signal averaging time (TSA) on on-line pulse oximetry used for overnight sleeprecordings. Am J Respir Crit Care Med 1996; 153: A714.

26. Mulloy E, McNicholas WT. Ventilation and gas exchange during sleep and exercise in severe COPD. Chest 1996; 109: 387–394.

27. Janssens JP, Howarth-Frey C, Chevrolet JC, Abajo B, Rochat T. Transcutaneous PCO2 to monitor non-invasive mechanicalventilation in adults: assessment of a new transcutaneous PCO2 device’ Chest 1998; 113: 768–773.

28. Bendjelid K, Schutz N, Stotz M, Gerard I, Suter PM, Romand GA. Transcutaneous PCO2 monitoring in critically ill adults. Clinicalevaluation of a new sensor. Crit Care Med 2005; 33: 2203–2206.

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REFERENCES




Model TCM4 TCM40 TCM400

Company Radiometer; Copenhagen Radiometer; Copenhagen Radiometer; Copenhagen

Website www.radiometer.com www.radiometer.com www.radiometer.com

Application Neonates to adults Neonates to adults Assess cutaneous oxygenation on up to 6 sites

Electrode(s) Ptc,CO2 – pH solid-state glass Ptc,CO2 – pH solid-state glass Ptc,O2 – 25 µm platinum. electrode. Stow-Severinghaus electrode. Stow-Severinghaus Clark-type O2 electrode. type CO2 electrode. type CO2 electrode.Ptc,O2 – 25 µm platinum. Ptc,O2 – 25 µm platinum. Clark-type O2 electrode. Clark-type O2 electrode.

Sp,O2 – Nellcor Probes.

Sensor temperature ºC Selectable between 37–45°C, Selectable between 37–45°C, Selectable between 37–45°C,in steps of 0.5°C in steps of 0.5°C in steps of 0.5°C

Membrane change – – –

Screen display Windows CE. Touchscreen Windows CE. Touchscreen Windows CE. Touchscreen technology. Normal view technology. Normal view technology. Normal view(numeric), trend table view, (numeric), trend table view, (numeric), trend table view,trend curve view trend curve view trend curve view

Alarms Adjustable low and high Adjustable low and high Adjustable low and high limits for PO2 and PCO2 limits for Sp,O2, PO2 and limits for PO2. Audible and Audible and visual alarm PCO2. Audible and visual visual alarm indicationindication alarm indication

Pt,CO2 range kPa 0.7–13.3 0.7–13.3 NA

Pt,CO2 accuracy kPa ±0.6 ±0.6 NA

Pt,O2 range kPa 0–99.9 0–99.9 0–99.9

Pt,O2 accuracy Range 0–21%: ±0.6 kPa Range 0–21%: ±0.6 kPa Range 0–21%: ±0.6 kPaRange 21–100%: ±10% Range 21–100%: ±10% Range 21–100%: ±10%

Sp,O2 range % NA 70–100 NA

Sp,O2 accuracy NA Adults: ±3% NANeonates: ±4%

Pulse range bpm NA 20–250 NA

Pulse accuracy bpm NA ±3 NA

Response time s <18 s for PO2 <18 s for PO2 <18 s for PO2<26 s for PCO2 <26 s for PCO2

Drift Pt,O2: ±5% over calibration Pt,O2: ±5% over calibration Pt,O2: ±5% over calibrationinterval Pt,CO2: ±10% over interval Pt,CO2: ±10% over intervalcalibration interval calibration interval

Calibration Auto-calibration. Integrated Auto-calibration. Integrated Auto-calibrationgas bottle. 1-point, 7.5% CO2 gas bottle. 1-point, 7.5% CO2and 20.9% O2, balance N2. and 20.9% O2, balance N2. 4-h calibration interval 4-h calibration interval recommended recommended

Battery Internal – 1 h Internal – 1 h Internal – 1 h

Weight kg Monitor + Ptc,CO2/Ptc,O2 Monitor + Ptc,CO2/Ptc,O2/ >4 kgmodule 4.58 Sp,O2 modules 4.78

Dimensions Monitor: 16 x 30.8 x 23 Monitor: 16 x 30.8 x 23 Monitor: 16 x 30.8 x 23(H x W x D) cm Ptc,CO2/Ptc,O2 module: Ptc,CO2/Ptc,O2 module:

10.7 x 14.5 x 14.8 10.7 x 14.5 x 14.8Sp,O2 module: 3.5 x 14.5 x 14.8

Outputs EIA232 EIA232Parallel port IEEE1284, Parallel port IEEE1284,Centronics printer port Centronics printer port

Data-logger 48 h of patient data 48 h of patient data

Software - - Data can be printed out ingraphical and numerical formReports can be obtained




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Model MicroGas 7650 Rapid TOSCA 500 SenTec

Company Radiometer; Copenhagen Radiometer; Copenhagen SenTec AG

Website www.radiometer.com www.radiometer.com www.sentec.ch

Application Noninvasive. Continuous, Noninvasive. Continuous, Adult and paediatric usereal time real time Noninvasive. continuous, real time

Electrode(s) Clark-type PO2 sensor combined Stow-Severinghaus-type V-Sign combined sensorwith Stow-Severinghaus-type PCO2 combined with Masimo Pt,CO2/Sp,O2/PulsePCO2 sensor SET® Sp,O2 pulse oximetry

Sensor temperature ºC Selectable between 37–45°C, Recommended: 42°C 42in steps of 0.5°C Selectable between 37–45°C,

in steps of 0.5°C

Membrane change Every 2 weeks Every 2 weeks Every 2 weeks

Screen display 3-digit LED displays for PO2 3-digit LED displays for TFT Colour Displayand PCO2. LCD display, PCO2, Sp,O2 and pulse rate Trend graphs or LED back-lit with adjustable 10-segment LED bar numerical data on contrast, for selectable graph for plethysmogram Pt,CO2, pulse, plethysmograph, parameters, messages and alarms Graphic LCD with LED Sp,O2

back-light and adjustable contrast for selectable parameters, messages and alarmsUser-selectable display mode for status, trend, plethysmogram and heating power

Alarms Adjustable low and high limits Adjustable low and high High/low PCO2, Sp,O2, pulsefor PO2 and PCO2 limits for PCO2, Sp,O2 and AC power/batteryAudible and visual alarm pulse rate Status messagesindication Audible and visual alarm

indication

Pt,CO2 range kPa 0.1–20 0–25 0–26.67

Pt,CO2 resolution kPa – 0.1 0.1

Pt,O2 range kPa 0.0–99.9 NA NA

Pt,O2 accuracy – NA NA

Sp,O2 range % NA 0–100 1–100

Sp,O2 accuracy NA 70–100%: ±3 digits 70–100%: ±2%

Sp,O2 signal averaging s NA 2, 4, 8, 10, 12, 14, 16 FastSat –

Pulse range bpm NA 25–240 30–250

Pulse accuracy bpm NA ±3 ±3

Response time s <25 s for PO2 <50 s for PCO2 <80 s for PCO2<60 s for PCO2

Drift <1%·h-1 <0.5%·h-1 < 1%·h-1

Calibration Fully automatic calibration Fully automatic calibration Gas bottle with docking stationTypical calibration time: 2 min Typical calibration time: 2 minIntegrated calibration chamber Integrated calibration chamber

Battery Internal – 1 h Internal – 1 h Internal – 6–7 h

Weight kg 5.6 5.3 2.5

Dimensions (HxWxD) cm 13.5 x 26.6 x 30 13.5 x 26.6 x 30 10.2 x 27 x 23

Outputs 1 x 37-way connector with 1 x 37-way connector with Digital: RE/EIA 232analogue output, RS 423 and analogue output, RS 423 Analogue: 0–1Vstatus signals 1 x 25-way connector 1 x 25-way connector with with Centronics Centronics parallel interface parallel interface

Data-logger Automatic storage of measured Automatic storage of 48 h internal memorypatient data over the last 18 h measured patient data over 240 h external memoryDownload to a printer or PC the previous 72 h

Reviewing trends on screenDownload to PC

Software Download 2001 V-STATS


trans cutaneous carbon dioxide and oxygen monitoring in the adult patient

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