260 Albrecht et al., Computed dip parameters II. Value of descriptive parameters

J. Perinat. Med.2 (1974) 260

Computed dip-parameters derivedfrom digitizedFHR-curvesII. The value of descriptive parameters

H. Albrecht, J. Bokelmann, J. Morgenstern, H. Schmidt

Universitäts Frauenklinik Düsseldorf (Head: Prof. Dr. L. BECK)Düsseldorf/Germany

Received February 26, 1974. Accepted July l, 1974.

The method of Computing simultaneously andobjectively numerous descriptive dip-parametersfrom digitized cardiotocograms (CTG) de-'scribed in Part I, allows a closer investigation ofthe content of clinical Information of single dip-parameters. This work focuses on the followingquestions:1. How do various dip-parameters behave

in the cardiotocograms of normal newbornsand of asphyxiated newborns ?

2. Is the frequency distribution of certaindip-parameters a function of the lag-timeor of the total area ?

l Materials and methodsFrom the year 1969 1,115 un-selected deliveriesmonitored by cardiotocography were analy2edretrospectively and coded. The code is based on15 characteristics of identification and 19 clinicalcriteria. In order to define the state of the new-born not only by the AP GAR score an extendednewborn asphyxia index was utilized for thecoding [4] (Fig. 1). Clinical portions of thisnewborn index are the AP GAR score at l, 5, and10 minutes, resuscitation measures, and theadaptation of the newborn in the first days oflife. The asphyxia index defines three groups:Index l includes newborns without disturbancesof adaptation, Index 2 newborns with a delayedadaptation and Index 3 identifies newborns witha severely disturbed adaptation up to seriousasphyxia. According to this index the 1,115

Curriculum vitae

Dr. HERBERT ALBRECHTwas bor n in 1939 in Berlin. Hestiidied medicine in Freiburgand Main% from 1960 to 1966and served a rotating internshipfrom 1966—1968. He under-went training in neonatalintensive care at the De-partment of Pediatrics at theUniversity of Düsseldorf y 1968to 1969. He is an assistantat the Department of Ob-stetrics and Gynecology at theUniversity of Düsseldorf since1969. His perinatal research focuses on the investigation of fetalheart frequency.

Index APGAR score Newborn condition

l min 7—10and 5 min 10and 10min 10

normal adaptation and noclinical deteriorationno need of neonatalintensive care

2

3

oror

oror

1 min 5 — 65 min 7— -9

10 min 9

1 min 1—45min 1 — 6

10min 1—8

reanimationno clinical deteriorationno need of neonatalintensive care

reanimationinsufficient adaptationneonatal intensive care

Fig. 1. The extended newborn asphyxia index for theassessment of the newborn in the first 7 days of life.

J. Perinat. Med. 2 (1974)

Albrecht et al., Computed dip parameters II. Valuc of descriptive parameters 261

deliveries were divided into two groups withnormal and pathologic newborn indices. Thepathological group contains all digitized CTGswith a newborn index of 2 or 3.For the normal group with a newborn index ofl, the selection of digitized cases was performedrandomly until the number of CTG minutes wasapproximately equal to that in the pathologicalgroup.The further evaluation comprised only thosecases in which the CTG contained contraction-related decelerations. Thus, in the normal groupthe number of patients was reduced to 105 with a

20

10

total of 575 decelerations and the pathologicgroup to 46 patients with 367 decelerations. Foreach of the areas of deceleration, the 30 para-meters described in Part I were available forfurther evaluation. From the multitude ofdescriptive parameters, only those parameterswere selected with which informed clinicians arefamiliär and which are easily understood byothers. Parameters thus examined are the area,amplitude, total duration, duration at halfamplitude, decrement time, duration at dipminimum, recovery time, lag time, andfluctuation within the dip.

4000TOTAL A R E A

sec

10

DURATION AT HALF A M P L I T U D E

100

TOTAL D U R A T I O N

_ N O R M . I N D E X 575 D I P S— PATH . I N D E X 367 D I P S

Fig. 2. Frequency distributions o£ dip area, lag time, duration at half amplitude and total duration from digitized CTGtracings with normal and pathological newborn index. Each parameter has been divided into 20 samples of equal size.The normal group is drawn in bold face.

J. Pcrinat. Mcd. 2 (1974)

262 Albrecht et al., Computed dip parameters 11. Value of descriptive parameters

The calculated values of each parameter weredivided into 20 samples of equal size for thepurpose of the study and graphically depicted inthe form of frequency distributions. For the sakeof easier understanding, the frequency distri-butions of the parameters of both groups wereentered into the same graph. The distributionsfor the pathologic group are drawn in thin linesand those for the normal group in bold face.The deviations of the distributions for both

groups are hatched. The variances in the fre-quency distributions of both groups for allparameters were tested with the chi-square test.

- t2 Results2.1 Frequency distributions of 9 descriptive

dip parametersThe frequency distributions for dip-area, lag-time, duration at half amplitude and total durationcan be seen in Fig. 2. The parameters of area,

20 sec

D U R A T I O N A T M I N I M U M

p< 5%

50D E C R E M E N T - T I M E

sec

p < 5e/.o

10

o//o

20

10«

p< 1 V.

100

R E C O V E R Y - T I M E

sec FHR

F L U C T U A T I O N W I T H I N— N O R M . I N D E X 575 DIPS

PATH . I N D E X 367 DIPS

Fig. 3. Frequency distribution of decrement time, duration at minimüm, recovery time, and fluctuation within the dip.

J. Perinat. Med. 2 (1974)

Albrecht et al., Computed dip paramcters II. Valuc of descriptivc parameters 263

total duration and duration at half amplitudeshow a shift towards high values in the CTGtracings with pathological newborn index. Thereappears to be a recognizable difference betweenthe two groups relative to the lag-time i. e.dips with pathological newborn index con-tain more dips with a lag-time of over 20seconds.Fig. 3 demonstrates the distribution for durationat minimum, decrement time, recovery time andfluctuation within the dip. Except for the ampli-tude of the decrement, all examined parameters aresignificantly different between the two. groups.

2.2 The dependence of the dip parameterfrom lag-time and area

The severity of CTG changes is judged by theclinician, particularly from the extent of the lag-time and the size of the dip area. For this reasonit is logical to ask whether certain dip parametersleading to an abnormal neonatal adaptationchange with increase of lag-time and area. Ithas been questioned whether decelerations with alarge lag-time in the group with a pathologicalnewborn index have a longer recovery time (i. e.,the time between dip-minimum and base-Jinefrequency) than decelerations with a short lag-

20

10

L A G - T I M E 0 - 20 sec

p < t */.. 20

10

L A G - T I M E 20sec

p < 1 %·

50— NORM. I N D E X £23 OIPS_ PATH . INDEX 213 DIPS

50• NORM. I N D E X.PATH. I N D E X

152 DIPS154 DIPS

D E C R E M E N T - T I M E

L A G - T I M E 0 - 20 sec

p < 5%

100 sec.NORM. I N D E X 423 DIPS. P A T H . I N D E X 213 DIPS

.NORM. INDEX 66 DIPS«PATH INDEX 61 DIPS

R E C O V E R Y - T I M E

Fig. 4. Frequency distribution for deceleration time and recovery time of decelerations with a small and a large lag time.

J. Pcrinat. Med. 2 (1974)

264 Albrecht et al., Computed dip parameters II. Value of descriptive parameters

time. With a lag-time over 20 seconds, higherdecrement times are found more often in thegroup with a pathological newborn index. With alag-time of over 40 seconds, the frequency distri-bution of the recovery times of the pathologicalgroup is markedly shifted to values with a longerrecovery time. Furthermore, these large lag-times (over 40 seconds) have more often anassociated loss of the normal beat-to-beat Vari-ation. This is seen clearly in the frequencydistribution for the fluctuation within the dip,with different lag-times (Fig. 4).The dependence from the lag-time has beentested for all discussed parameters. Tab. I sum-marizes the results. The examined dip-parametersare listed in the left column of the table.The first column lists the significant differencesfor all examined dip-parameters between the twogroups without selection äs to lag-times. The

' ' following three columns are based on limitinglag-times of 0—20, 21—40, and over 40 seconds.There was no correlation between lag-timeand area, amplitude, and duration at mini·*mum. CTGs with a pathological newborn indexdemonstrated a correlation between lag-timeand recovery time, total duration and fluc-tuation within the dip.The total area was examined similarly with asimilar division of the total area in three groups.There was no alteration of the frequency distri-bution for certain parameters in the two groups.This means that in contrast to a long lag-time

Tab. I. The statistically significant differences (X2 test) ofthe frequency distributions of dip parameters in the groupswith a normal and a pathological newborn index. Column lcontains the significant differences for all decelerations.Columns 2, 3, and 4 contain significant differences for thedecelerations with lag-times of 0—20, 21—40 seconds,and over 40 seconds. (An empty field denotes no significantdifferences.)

dip-parameter totallag-time (sec)

0—20 21—40 >40

Total areaDecrement-timeDuration at

minimumRecovery-timeDuration at half

amplitudeTotal durationFluctuation

within

<5°/, o

<5 o <5%0

5%

the fluctuation does not decrease with largetotal areäs and a pathological newbornindex.

3 CommentaryThe Interpretation of decelerations for thediagnosis of the fetal Status is generally carriedout according to CALDEYRO-BARCIA [5] by type Iand type II dips or by the deceleration typesdescribed by HON [9] of head and cord com-

20

10

LAG - T I M E 0 -20sec

N.S.20

10

L A G - T I M E 2 1 - 4 0 sec

5V.

L A G - T I M E 40 sec

NORM. I N D E X A23 DIPS FHR

PATH. I N D E X 213 DIPS— NORM.INDEX 86 DIPS FHR

_ P A t H . INDEX 93 DIPS

10

— NORM.INDEX 66 DIPS FHR

^ PATH.INDEX 61 DIPS

F L U C T U A T I O N W I T H I N

Fig. 5. Loss of fluctuation with increasing lag time.

j. Perinat. Med. 2 (1974)

Albrccht et al., Computed dip parameters II. Valuc of descriptive parameters 265

pression and utero-placental insufficiency patterns.The informational content of single dip para-meters by which the decelerations may be dif-ferentiated by their form in regard to the oc-currence of fetal distress, remains largely dis-regarded by these schemes, although manyauthors have pointed out the importance ofduration of lag-time, amplitude, duration andnumber of preceding decelerations [2, 3, 6, 7, 8,10, 12, 13, 14, 15, 17]. These authors found thatthere was a correlation between the increaseof these dip-parameters and the degree ofacidosis or state of the newborn. SHELLEY andTIPTON [16] found that the decisive parameterfor the assessment of the fetus was the sum ofthe total area of the dips.While this did lead to a simplification of the Inter-pretation of cardiotocograms, the power of aprecise objective Statement was lost becausenumerous important parameters such äs the lossof fluctuation within the dip [7] was disregarded.

In order to Interpret CTGs more objectively,KIMURA [11] differentiated the distribution of thebase line frequency, lag-time, amplitude, durationand recovery time of the deceleration äs well äsvarious fluctuation types of the base line fre-quency in samples with various AP GAR and acid-base values. The examined FHR parameters wereentered into an FHR score in order to assess thefetal state better.Our examinations show that 8 of the 9 selecteddescriptive dip-parameters were significantlydifferent in their frequency distributionsbetween a normal and a pathological groups.This effect is reinforced for some parameters ifonly dips with a lag-time of over 40 seconds areselected for the examination. This particular resultemphasizes the importance of the lag-time forthe assessment of the state of the fetus. How-ever, a rank order of importance for the ex-amined descriptive parameters cannot bederived from our results.

SummaryThe frequency distribution of 9 descriptive parameters incardiotocograms (CTG) in groups with normal andpathological newborn states was calculated and comparedstatistically. For the assessment of the state of the newbornan extended newborn asphyxia index was establishedwhich considers, in addition t o the APGAR score at 1,5, and10 minutes, the course of the newborn in the first 7 days oflife (Fig. 1). The recorded CTGs were digitized andprocessed according to the method described in Part I.The group with a normal newborn index contains thedigitized CTG tracings from 105 patients with 575 de-celerations and the group with a pathological newbornindex from 46 patients with 367 decelerations. It is shownthat the CTG tracings with a pathological newbornindex have significantly more decelerations withlarger areas and larger lag-time, duration at halfamplitude and total duration (Fig. 2), decrement time,

duration at minimum, recovery time, and a decreaseof the fluctuation within the dip (Fig. 3). For some ofthe examined parameters the difference in frequencydistribution is even more marked in the two groups ifonly decelerations with a long lag-time are admitted(Fig. 4). With a lag-time of over 20 seconds, an increase ofthe decelerations with a large decrement time, total duration,and duration at half amplitude and CTG tracings with apathological newborn index was found. Decelerations witha lag-time of over 40 seconds with a subsequent patho-logical post-partum adaptation are frequently characterizedby a considerable loss in fluctuation (Fig. 5). The resultsshow that for the Interpretation of decelerations, manyparameters must be considered. The relative importancefor the assessment of the fetal state among the examineddescriptive parameters cannot be derived from our results.

Keywords: Asphyxia index, digitized data, electronic data processing, fetus, frequency distribution, parameters of de-celeration.

ZusammenfassungComputer-Auswertung von Dip-Parametern aus digi-talisierten fetalen Herzfrequenz-Kurven. II. Die Be-wertung deskriptiver ParameterEs wurde die Häufigkeitsverteilung von 9 beschreibendenDip-Parametern in Kardiotokogrammen (CTG) mitnormalem und pathologischem Neugeborenen-Zustandermittelt und statistisch verglichen. Zur Beurteilung desNeugeborenen-Zustandes wird ein erweiterter Neuge-borenen-Asphyxie-Index, der neben dem ArGAR-Score

nach l, 5 und 10 Minuten den Verlauf des Neugeborenenin den ersten 7 Lebenstagen berücksichtigt, gebildet(Fig. 1). Die geschriebenen CTG's werden nach dem inTeil I dargestellten Verfahren digitalisiert und ausge-wertet. Das Kollektiv mit einem normalen Neugeborenen-Index enthält die digitalisierten CTG-Verläufe von 105Patienten mit 575 Dezelerationen und das Kollektiv mitpathologischem Neugeborenen-Index, die von 46 Pa-tienten mit 367 Dezelerationen. Es zeigt sich, daß in

J. Pcrinat. Mcd. 2 (1974) 19

266 Albrecht et al., Computed dip parameters II. Value of descriptive parameters

CTG-Verläufen mit einem pathologischen Neuge-borenen-Index signifikant häufiger Dezelerationenmit größeren Flächen, einer größeren lag-time, Dauetbei halber Dip-Tiefe, Gesamtdauer (Fig. 2), Abstiegs-zeit, Dauer im Dip-Minimum, Anstiegszeit und eineEinschränkung der Fluktuation im Dip (Fig. 3) vor-kommen. Für einen Teil der untersuchten Parameternimmt der Unterschied bezüglich der Häufigkeitsvertei-lungen in den beiden Kollektiven zu, wenn nur Dezele-rationen mit einer großen lag-time zugelassen werden(Fig. 4). Bei einer lag-time ab 20 sec wird eine Zunahmeder Dezelerationen mit einer großen Anstiegszeit, Gesamt-

dauer und Dauer bei halber Dip-Tiefe in CTG-Verläufenmit einem pathologischen Neugeborenen-Index gefunden.Dezelerationen mit einer lag-time über 40 sec, die eineAnpassungsstörung post partum zufolge haben, sindhäufig durch einen erheblichen Fluktuationsverlust cha-rakterisiert (Fig. 5). Die Ergebnisse zeigen, daß für dieBeurteilung der Dezelerationen die Berücksichtigungvieler Parameter notwendig ist. Eine unterschiedlicheRangordnung für die Beurteilung des fetalen Zustandesläßt sich jedoch aus den untersuchten beschriebenenParametern durch die gefundenen Ergebnisse nicht ab-leiten.

Schlüsselwörter: Asphyxie-Index, Dezelerationen, Dezelerations-Parameter, digitalisierte Daten, Elektronische Daten-verarbeitung, Fet, Häufigkeitsverteilungen.

ResumeLes parametres Dip computes derives decourbesFHRdigitalisees II. Yaleur des parametres descriptifsLe present article expose avec conii-ontation «tatist'ique ladistribution de frequence de 9 parametres descriptifs encardiotocogrammes (CTG) avec etat normal et pathologiquedes nouveaux-nes. Pour Tappreciation de l'etat du nouveau-ne, on a elabore un index elargi d'asphyxie du nouveau-ne qui, a cöte du Score APGAR apres l, 5 et 10 minutes,suit l'evolution du nouveau-ne durant les sept premiersjours (Fig. 1). Les CTG enregistres sont digitalises etevalues d'apres la methode exposee au chapitre I. Legroupe de l'index normal de nouveau-ne comprend lestraces de CTG digitalises de 105 patients avec 575 de-celerations et le groupe de l'index pathologique de nouveau-ne ceux de 46 patients avec 367 decelerations. On observedans les traces de CTG avec index pathologique denouveau-ne des decelerations beaucoup plus fre-quentes avec surfaces plus etendues, un lag-time plusgrand, de meme duree pour une demie profondeurDip, la duree totale (Fig. 2), le temps de decroissance, la

duree dans le minimum Dip, le temps de croissance et unerestriction de la fluctuation dans le Dip (Fig. 3). Pour unepartie des* parametres analyses, la difference relative auxdistributions de frequence dans les deux groupes augmentea condition seulement de decelerations avec un grand lag-time (Fig. 4). Pour un lag-time partant de 20 sec, on ob^·serve un accroissement des decelerations avec un temps decroissance, une duree totale et une duree pour demieprofondeur Dip eleves dans les traces de CTG avec indexpathologique de nouveau-ne. Les decelerations avec unlag-time superieur a 40 sec, qui provoquent une ad-aptation pathologique post partum, se caractorisent fre-quemment par une perte de fluctuation considerable(Fig. 5). Les resultats montrent la necessite de tenir comptede beaucoup de parametres pour pouvoir evaluer lesdecelerations. Les resultats obtenus a la suite de l'analysedes parametres decrits ne permettent pas, toutefois, d'etablir une classification differentielle pour rappreciationde l'etat foetal.

Mots-cles: Decelerations, distributions de frequence, donnees digitalisees, foetus, index d'asphyxie, parametre de de-leleration, traitement electronique des donnees.

Acknowledgement

This work was supported by the Bureau of Research, Ministry of Science and Research, State of Northrhine-Westphalia.

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[15] MORGENSTERN, J., H. ALBRECHT, J. BOKELMANN,H. SCHMIDT: Computed dip-parameters dirived fromdigistized FHR-curves. Part I. The describing para-meters and the method of digitizing. T- Perinat. Med.2 (1974) 254

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Dr. med. Herbert AlbrechtUniversitäts-FrauenklinikMoorenstraße 5D-4000 Düsseldorf/Germany

J. Perinat. Med. 2 (1974) 19*