80 Original Paper
The Factor Time in Fetal Heart Rate Monitoring and the Detection of Acidosis Using the WAS Score
Authors
V. M. Roemer, R. Walden
Affiliation
Institute of feto-maternal medicine, Detmold, Germany
Key words ▶ time in fetal monitoring ● ▶ WAS score ● ▶ fetal heart frequency ● ▶ microfluctuation ● ▶ oscillation-amplitude ●
Abstract
Zusammenfassung
Background: Using the naked eye evaluation of fetal heart rate (fhr) patterns remains difficult and is not complete. Computer-aided analysis of the fhr offers the opportunity to analyze fhr patterns completely and to detect all changes due to hypoxia and acidosis. It was the goal of this study to analyze the factor time in fetal monitoring and to evaluate the association between the fhr and the actual pH values in arterial umbilical blood. Methods: During a period of 11 years the FHR signals (i. e., the R-R interval of the F-ECG) of 646 fetuses were recorded with a CTG and simultaneously by a computer. The computer files were analyzed thereafter, i. e., the results did not influence our clinical management. To enter the study, all fetuses must have been delivered by the vaginal route – in consequence without a significant loss of fhr signals. During forceps and/or vacuum deliveries recordings were continued. If necessary a new electrode was inserted. In this study recordings of fetuses with chorioamnionitis, tracings of malformed neonates and tracings shorter than 30 min were excluded. Thus 484 recordings were left. We used our own computer programs written in MATLAB (USA). 3 parameters were determined electronically: 1) the mean fetal frequency [fhf, (bpm)], 2) the number of turning points (N/min) in the fhr, which we called ‘microfluctuation’ (micro) and 3) the oscillation amplitude, oamp (bpm). Measurements of the acid-base variables from arterial (UA) and venous (UV) blood were performed using RADIOMETER equipment (ABL500) and trained personnel. However, only the actual pHUA values were used in this study. To detect the influence of hypoxia and acidosis, all 484 cases were separated into 7 groups according to the actual pHUA value: 55 fetuses lying in a small non-acidotic “pH-window” (pHUA = 7.290–7.310, mean = 7.300 ± 0.008) were used as ‘controls’.
Hintergrund: Die Beurteilung der fetalen Herzfrequenz (FHF) mit dem normalen Auge ist und bleibt schwierig; sie ist vor allem nicht vollständig. Die Computeranalyse der FHF ermöglicht eine genauere Darstellung und hilft Veränderungen bedingt durch Hypoxie und Azidose deutlicher zu erkennen. Ziel dieser Arbeit war es den Faktor Zeit genauer zu untersuchen und den Zusammenhang zwischen den Variablen der FHF und den aktuellen pHNA-Werten darzustellen. Methoden: Während eines Zeitraumes von 11 Jahren wurde das direkt abgeleitete Signal der FHF (der R-Zackenabstand im fetalen EKG) von 646 Feten elektronisch registriert. Diese Aufzeichnungen hatten keinen nennenswerten Einfluss auf den späteren Geburtsverlauf. In dieser Studie wurden nur die letzten 30 min von Feten analysiert, die auf vaginalem Weg zur Welt gekommen waren, d. h. also ohne deutlichen Signalverlust. Während einer Vacuum- und/oder Zangenextraktion wurde die Überwachung fortgesetzt. Bei Bedarf wurde eine neue Elektrode gelegt. CTGs von Feten mit Chorioamnionitis, Fehlbildungen und Aufzeichnungen kürzer als 30 min wurden ausgeschlossen. So verblieben 484 Fälle, die mit eigenen Computerprogrammen (MATLAB, (USA)) ausgewertet werden konnten. Messungen des fetalen Säure-Basen Haushaltes wurden von geschultem Personal mit Geräten (ABL500) der Firma RADIOMETER vorgenommen. In dieser Arbeit wurden nur die aktuellen pHNA-Werte verwendet. Die 484 Feten wurden nach ihrem pHNA-Wert in 7 Gruppen aufgeteilt. Zur Kontrolle dienten 55 Feten, die mit ihrem pH in einem engen „pH-Fenster“ lagen, (pHNA: 7.290–7.310, Mittel = 7.300 ± 0.008). Resultate: Beim Menschen verhalten sich während der letzten 30 Geburtsminuten die Variablen Mikrofluktuation (micro), Oszillationsam-
Schlüsselwörter ▶ Zeitanalyse: 30 min ante ● partum ▶ WAS-Score ● ▶ fetale Herzfrequenz (FHF) ● ▶ Mikrofluktuation der FHF ● ▶ Oszillationsamplitude der ● FHF
received 15.11.2013 accepted 11.03.2014 after revision Bibliography DOI http://dx.doi.org/ 10.1055/s-0034-1372596 Z Geburtsh Neonatol 2014; 218: 80–86 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0948-2393 Correspondence Prof. Dr. Volker Michael Roemer Institute of feto-maternal medicine Benekestraße 2 32756 Detmold Germany Tel.: + 49/5231/35 842 Fax: + 49/5231/34 006 [email protected]
▼
Roemer VM, Walden R. The Factor Time in … Z Geburtsh Neonatol 2014; 218: 80–86
▼
Downloaded by: University of British Columbia. Copyrighted material.
Der Faktor Zeit bei der fetalen Überwachung und die Diagnostik einer Azidose durch den WAS-Score
Results: In humans fhf, micro and the oamp behave differently during the last 30 min of delivery and with different fetal pHUA values: micro is early (at 0 min) decreased with fetal acidemia and is steadily deceasing (68–40 N/min) during vaginal delivery; the oamp – mainly due to decelerations – is increased from 35 up to 70 bpm during the last 30 min. Hypoxia and acidosis increase the amplitude and duration of decelerations; finally fhf shows only an insignificant reaction to acidemia but is decreased (from 135 to 110 bpm) overall with the course of time. Therefore the 3 characteristics of the fhr might be ranged according to their decreasing sensitivity to acidemia as follows: 1) fetal microfluctuation, 2) oscillation amplitude and 3) mean frequency. The 3 components of the fhr were used to invent and apply a score named the WAS score. This score increases the association between the actual pHUA values and the activity of the fetal heart. The 3 variables of the fhr mentioned above were rated differently; the 3 factors necessary to achieve this were computed electronically using an optimization program. The result is the WAS score: WAS = mean [frq*ff(vj) * micro*fm (vj)/oamp*fa(vj)]j = 1,30. Using the last 30 min of delivery the correlation coefficient r of this score with pHUA reaches 0.645, P < < 0.001. The regression is linear in our 484 cases. Conclusions: Microfluctuation is the most sensible variable of the fetal heart followed by the oscillation amplitude and mean frequency. The WAS score offers the best correlation with the actual pH values measured in arterial umbilical blood.
plitude (oamp) und basales Frequenzniveau (fhf) unterschiedlich: Sowohl der Faktor Zeit als auch die Azidämie beeinflussen diese Werte: Die Micro ist bei einer Azidose schon 30 min ante partum (etwas) reduziert und fällt mit zunehmender Zeit stetig weiter ab [von 68 auf ca. 39 (N/min)]; die Oamp (hervorgerufen durch Dezelerationen) nimmt während der letzten halben Stunde deutlich zu [von 35 auf 70 (bpm)]. Die fhf zeigt eine nur geringe Reaktion auf die Azidose nimmt aber über der Zeit stetig [von 135 auf 110 (bpm)] ab. Die 3 Variablen der fhf können daher nach abnehmender Sensitivität geordnet werden: 1.) Fetale Mikrofluktuation, 2.) Oszillationsamplitude und 3.) mittleres Frequenz-niveau. Diese Veränderungen sind mehrheitlich nur mit einem Computer verifizierbar. Diese 3 Variablen wurden verwandt um einen Score zu formulieren, der den engen Zusammenhang mit den pHNA-Werten deutlich macht: Die 3 Variablen der FHF werden dabei numerisch ganz unterschiedlich bewertet. Die Bewertungsfaktoren wurden elektronisch berechnet. Der neue Score heißt WAS-Score und lautet: WAS = Mittelwert [frq*ff(vj) * micro*fm (vj)/oamp*fa (vj)]j = 1,30. Der Korrelationskoeffizient r für das aktuelle pHNA beträgt jetzt 0,645, P < < 0,001; die Regressionsgerade ist linear (N = 484). Schlussfolgerung: Die Microfluktuation ist die sensibelste Variable der fetalen Herzfrequenz gefolgt von der Oszillationsamplitude (Dezellerationen + Akzelerationen) und der fetalen Basalfrequenz. Der WAS-Score zeigt bisher die engste Korrelation mit den aktuellen pH-Werten im Nabelarterienblut.
Background
all 484 cases to develop a prediction method to decide (still with a certain level of uncertainty) whether an fhf recording represents an acidosis or not. The first parameter is the mean frequency (frq) computed for each of the last 30 min. Thus we get 30 values, denoted frqi = 1,30. The second parameter is the microfluctuation (micro), which represents the number of extremes (maxima and minima) during one CTG minute. During the last 30 min we get 30 values, one value for each minute, denoted micro i = 1,30. The third parameter is the oscillation amplitude (oamp) of the fhf curve computed again for each of these 30 CTG minutes, oamp i = 1,30. This amplitude is the difference between the maximal und minimal values of the fhf in the specified minute. For a better understanding a summary of the variables which ▶ Fig. 1. These 3 variwere determined in this study is given in ● ables amount to 3 × 30 = 90 data points for each fhf minute. Since our archive contains 484 cases, we have 3 × 30 × 484 = 43 560 data points to handle for achieving our aim.
▼
Since more than half a century, monitoring of the fetal heart frequency (fhf) has become an important tool in the management of human delivery. Usually the fhf signal is displayed on a screen or is printed using a paper strip. If we include a computer record we can also analyze the fhf values electronically aiming to compute a score. In former times some scores were designed to read off the fetal state from the value of the fhf score. Usually quantities like the fhf bandwidth of the baseline, the number of fhf crossings of the baseline, the number and size of decelerations and accelerations were counted using a time interval of 30 min. The problem of such types of scores is which fhf variables to include and how to define the interesting intervals and the number of points to award. Even to add the points remains problematic. Until now no standard was defined. In this paper we present a score based on quite different principles with the goal to predict the pH value in arterial umbilical blood (pHUA). To achieve this we first look at 3 parameters derived from the fhf during the last 30 min of delivery. These variables are: mean frequency, microfluctuation and the oscillation amplitude. Using these 3 parameters we want to predict the pHUA values at delivery. We use a computer and an optimization program. In our last study [1] the factor time was used in the sense of “duration of the record”; time was excluded just by keeping it constant: always only the last 30 CTG min were analyzed. In this paper we want to introduce time in the sense of “elapsed time” of the last 30 min running from 0 to 30 min. Moreover, we wish to explain a possibility of electronic fhf evaluation with respect to fetal acidemia by introducing a CTG score. Our archive of fhf recordings amounts to 484 cases with fetal pH values measured soon (5–10 min) after delivery. We used nearly
Material and Methods
▼
The fhf signals (i. e., the R-R intervals in the F-ECG) of 637 fetuses were recorded by a Hewlett-Packard CTG (8040 A). During a period of 11 years (2000–2010) all recordings were realized in the Frauenklinik of the Klinikum Lippe Detmold GmbH [East Westfalia/Lippe, Germany, (Head in the past: Prof. Dr. V. M. Roemer)] still including some premature infants (N = 5). To enter the study all fetuses must have been delivered by the vaginal route – therefore without a significant loss of fhf signals. During forceps and/or vacuum delivery FHR recordings were continued. Short-lasting ( < 20 s) signal losses were overcome by signal-repair algorithms developed in our institution [2]. In a small number of cases a new electrode was inserted. Recordings Roemer VM, Walden R. The Factor Time in … Z Geburtsh Neonatol 2014; 218: 80–86
Downloaded by: University of British Columbia. Copyrighted material.
Original Paper 81
82 Original Paper
Fig. 1 Diagram of only one CTG minute enlarged showing the 3 variables, which are determined electronically. The total number of turning points/ min (2 points are indicated by arrows) represents the parameter ‘microfluctuation’.
FHF: Mean frequency (133.6 bpm), Osc.- amplitude : (142 – 125.5= 16.5 bpm), Number of turning points (labelled with arrows): N= 61/Min
FETAL HEART FREQUENCY (bpm)
3
142
CTG-44180004.CTX
4
142 140 138 136 134
133.6
132 130 128
Turning point
126 32
33
34 35 36 TIME INTERVAL (Minutes)
37
38
39
4
Fig. 2 The fetal heart frequency is decreased during the last 30 min of delivery; this is predominantly due to the factor time itself and most probably not due to hypoxia and acidosis. Only more severe acidosis leads intermittently to episodes of bradycardia (cases with very high pH values (pH > 7.405, N = 3) were omitted).
The last 30 - Minutes of 481 fetuses with 14 430 CTG - Min ; red : 6.960≤ pH,UA
The Factor Time in Fetal Heart Rate Monitoring and the Detection of Acidosis Using the WAS Score
Authors
V. M. Roemer, R. Walden
Affiliation
Institute of feto-maternal medicine, Detmold, Germany
Key words ▶ time in fetal monitoring ● ▶ WAS score ● ▶ fetal heart frequency ● ▶ microfluctuation ● ▶ oscillation-amplitude ●
Abstract
Zusammenfassung
Background: Using the naked eye evaluation of fetal heart rate (fhr) patterns remains difficult and is not complete. Computer-aided analysis of the fhr offers the opportunity to analyze fhr patterns completely and to detect all changes due to hypoxia and acidosis. It was the goal of this study to analyze the factor time in fetal monitoring and to evaluate the association between the fhr and the actual pH values in arterial umbilical blood. Methods: During a period of 11 years the FHR signals (i. e., the R-R interval of the F-ECG) of 646 fetuses were recorded with a CTG and simultaneously by a computer. The computer files were analyzed thereafter, i. e., the results did not influence our clinical management. To enter the study, all fetuses must have been delivered by the vaginal route – in consequence without a significant loss of fhr signals. During forceps and/or vacuum deliveries recordings were continued. If necessary a new electrode was inserted. In this study recordings of fetuses with chorioamnionitis, tracings of malformed neonates and tracings shorter than 30 min were excluded. Thus 484 recordings were left. We used our own computer programs written in MATLAB (USA). 3 parameters were determined electronically: 1) the mean fetal frequency [fhf, (bpm)], 2) the number of turning points (N/min) in the fhr, which we called ‘microfluctuation’ (micro) and 3) the oscillation amplitude, oamp (bpm). Measurements of the acid-base variables from arterial (UA) and venous (UV) blood were performed using RADIOMETER equipment (ABL500) and trained personnel. However, only the actual pHUA values were used in this study. To detect the influence of hypoxia and acidosis, all 484 cases were separated into 7 groups according to the actual pHUA value: 55 fetuses lying in a small non-acidotic “pH-window” (pHUA = 7.290–7.310, mean = 7.300 ± 0.008) were used as ‘controls’.
Hintergrund: Die Beurteilung der fetalen Herzfrequenz (FHF) mit dem normalen Auge ist und bleibt schwierig; sie ist vor allem nicht vollständig. Die Computeranalyse der FHF ermöglicht eine genauere Darstellung und hilft Veränderungen bedingt durch Hypoxie und Azidose deutlicher zu erkennen. Ziel dieser Arbeit war es den Faktor Zeit genauer zu untersuchen und den Zusammenhang zwischen den Variablen der FHF und den aktuellen pHNA-Werten darzustellen. Methoden: Während eines Zeitraumes von 11 Jahren wurde das direkt abgeleitete Signal der FHF (der R-Zackenabstand im fetalen EKG) von 646 Feten elektronisch registriert. Diese Aufzeichnungen hatten keinen nennenswerten Einfluss auf den späteren Geburtsverlauf. In dieser Studie wurden nur die letzten 30 min von Feten analysiert, die auf vaginalem Weg zur Welt gekommen waren, d. h. also ohne deutlichen Signalverlust. Während einer Vacuum- und/oder Zangenextraktion wurde die Überwachung fortgesetzt. Bei Bedarf wurde eine neue Elektrode gelegt. CTGs von Feten mit Chorioamnionitis, Fehlbildungen und Aufzeichnungen kürzer als 30 min wurden ausgeschlossen. So verblieben 484 Fälle, die mit eigenen Computerprogrammen (MATLAB, (USA)) ausgewertet werden konnten. Messungen des fetalen Säure-Basen Haushaltes wurden von geschultem Personal mit Geräten (ABL500) der Firma RADIOMETER vorgenommen. In dieser Arbeit wurden nur die aktuellen pHNA-Werte verwendet. Die 484 Feten wurden nach ihrem pHNA-Wert in 7 Gruppen aufgeteilt. Zur Kontrolle dienten 55 Feten, die mit ihrem pH in einem engen „pH-Fenster“ lagen, (pHNA: 7.290–7.310, Mittel = 7.300 ± 0.008). Resultate: Beim Menschen verhalten sich während der letzten 30 Geburtsminuten die Variablen Mikrofluktuation (micro), Oszillationsam-
Schlüsselwörter ▶ Zeitanalyse: 30 min ante ● partum ▶ WAS-Score ● ▶ fetale Herzfrequenz (FHF) ● ▶ Mikrofluktuation der FHF ● ▶ Oszillationsamplitude der ● FHF
received 15.11.2013 accepted 11.03.2014 after revision Bibliography DOI http://dx.doi.org/ 10.1055/s-0034-1372596 Z Geburtsh Neonatol 2014; 218: 80–86 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0948-2393 Correspondence Prof. Dr. Volker Michael Roemer Institute of feto-maternal medicine Benekestraße 2 32756 Detmold Germany Tel.: + 49/5231/35 842 Fax: + 49/5231/34 006 [email protected]
▼
Roemer VM, Walden R. The Factor Time in … Z Geburtsh Neonatol 2014; 218: 80–86
▼
Downloaded by: University of British Columbia. Copyrighted material.
Der Faktor Zeit bei der fetalen Überwachung und die Diagnostik einer Azidose durch den WAS-Score
Results: In humans fhf, micro and the oamp behave differently during the last 30 min of delivery and with different fetal pHUA values: micro is early (at 0 min) decreased with fetal acidemia and is steadily deceasing (68–40 N/min) during vaginal delivery; the oamp – mainly due to decelerations – is increased from 35 up to 70 bpm during the last 30 min. Hypoxia and acidosis increase the amplitude and duration of decelerations; finally fhf shows only an insignificant reaction to acidemia but is decreased (from 135 to 110 bpm) overall with the course of time. Therefore the 3 characteristics of the fhr might be ranged according to their decreasing sensitivity to acidemia as follows: 1) fetal microfluctuation, 2) oscillation amplitude and 3) mean frequency. The 3 components of the fhr were used to invent and apply a score named the WAS score. This score increases the association between the actual pHUA values and the activity of the fetal heart. The 3 variables of the fhr mentioned above were rated differently; the 3 factors necessary to achieve this were computed electronically using an optimization program. The result is the WAS score: WAS = mean [frq*ff(vj) * micro*fm (vj)/oamp*fa(vj)]j = 1,30. Using the last 30 min of delivery the correlation coefficient r of this score with pHUA reaches 0.645, P < < 0.001. The regression is linear in our 484 cases. Conclusions: Microfluctuation is the most sensible variable of the fetal heart followed by the oscillation amplitude and mean frequency. The WAS score offers the best correlation with the actual pH values measured in arterial umbilical blood.
plitude (oamp) und basales Frequenzniveau (fhf) unterschiedlich: Sowohl der Faktor Zeit als auch die Azidämie beeinflussen diese Werte: Die Micro ist bei einer Azidose schon 30 min ante partum (etwas) reduziert und fällt mit zunehmender Zeit stetig weiter ab [von 68 auf ca. 39 (N/min)]; die Oamp (hervorgerufen durch Dezelerationen) nimmt während der letzten halben Stunde deutlich zu [von 35 auf 70 (bpm)]. Die fhf zeigt eine nur geringe Reaktion auf die Azidose nimmt aber über der Zeit stetig [von 135 auf 110 (bpm)] ab. Die 3 Variablen der fhf können daher nach abnehmender Sensitivität geordnet werden: 1.) Fetale Mikrofluktuation, 2.) Oszillationsamplitude und 3.) mittleres Frequenz-niveau. Diese Veränderungen sind mehrheitlich nur mit einem Computer verifizierbar. Diese 3 Variablen wurden verwandt um einen Score zu formulieren, der den engen Zusammenhang mit den pHNA-Werten deutlich macht: Die 3 Variablen der FHF werden dabei numerisch ganz unterschiedlich bewertet. Die Bewertungsfaktoren wurden elektronisch berechnet. Der neue Score heißt WAS-Score und lautet: WAS = Mittelwert [frq*ff(vj) * micro*fm (vj)/oamp*fa (vj)]j = 1,30. Der Korrelationskoeffizient r für das aktuelle pHNA beträgt jetzt 0,645, P < < 0,001; die Regressionsgerade ist linear (N = 484). Schlussfolgerung: Die Microfluktuation ist die sensibelste Variable der fetalen Herzfrequenz gefolgt von der Oszillationsamplitude (Dezellerationen + Akzelerationen) und der fetalen Basalfrequenz. Der WAS-Score zeigt bisher die engste Korrelation mit den aktuellen pH-Werten im Nabelarterienblut.
Background
all 484 cases to develop a prediction method to decide (still with a certain level of uncertainty) whether an fhf recording represents an acidosis or not. The first parameter is the mean frequency (frq) computed for each of the last 30 min. Thus we get 30 values, denoted frqi = 1,30. The second parameter is the microfluctuation (micro), which represents the number of extremes (maxima and minima) during one CTG minute. During the last 30 min we get 30 values, one value for each minute, denoted micro i = 1,30. The third parameter is the oscillation amplitude (oamp) of the fhf curve computed again for each of these 30 CTG minutes, oamp i = 1,30. This amplitude is the difference between the maximal und minimal values of the fhf in the specified minute. For a better understanding a summary of the variables which ▶ Fig. 1. These 3 variwere determined in this study is given in ● ables amount to 3 × 30 = 90 data points for each fhf minute. Since our archive contains 484 cases, we have 3 × 30 × 484 = 43 560 data points to handle for achieving our aim.
▼
Since more than half a century, monitoring of the fetal heart frequency (fhf) has become an important tool in the management of human delivery. Usually the fhf signal is displayed on a screen or is printed using a paper strip. If we include a computer record we can also analyze the fhf values electronically aiming to compute a score. In former times some scores were designed to read off the fetal state from the value of the fhf score. Usually quantities like the fhf bandwidth of the baseline, the number of fhf crossings of the baseline, the number and size of decelerations and accelerations were counted using a time interval of 30 min. The problem of such types of scores is which fhf variables to include and how to define the interesting intervals and the number of points to award. Even to add the points remains problematic. Until now no standard was defined. In this paper we present a score based on quite different principles with the goal to predict the pH value in arterial umbilical blood (pHUA). To achieve this we first look at 3 parameters derived from the fhf during the last 30 min of delivery. These variables are: mean frequency, microfluctuation and the oscillation amplitude. Using these 3 parameters we want to predict the pHUA values at delivery. We use a computer and an optimization program. In our last study [1] the factor time was used in the sense of “duration of the record”; time was excluded just by keeping it constant: always only the last 30 CTG min were analyzed. In this paper we want to introduce time in the sense of “elapsed time” of the last 30 min running from 0 to 30 min. Moreover, we wish to explain a possibility of electronic fhf evaluation with respect to fetal acidemia by introducing a CTG score. Our archive of fhf recordings amounts to 484 cases with fetal pH values measured soon (5–10 min) after delivery. We used nearly
Material and Methods
▼
The fhf signals (i. e., the R-R intervals in the F-ECG) of 637 fetuses were recorded by a Hewlett-Packard CTG (8040 A). During a period of 11 years (2000–2010) all recordings were realized in the Frauenklinik of the Klinikum Lippe Detmold GmbH [East Westfalia/Lippe, Germany, (Head in the past: Prof. Dr. V. M. Roemer)] still including some premature infants (N = 5). To enter the study all fetuses must have been delivered by the vaginal route – therefore without a significant loss of fhf signals. During forceps and/or vacuum delivery FHR recordings were continued. Short-lasting ( < 20 s) signal losses were overcome by signal-repair algorithms developed in our institution [2]. In a small number of cases a new electrode was inserted. Recordings Roemer VM, Walden R. The Factor Time in … Z Geburtsh Neonatol 2014; 218: 80–86
Downloaded by: University of British Columbia. Copyrighted material.
Original Paper 81
82 Original Paper
Fig. 1 Diagram of only one CTG minute enlarged showing the 3 variables, which are determined electronically. The total number of turning points/ min (2 points are indicated by arrows) represents the parameter ‘microfluctuation’.
FHF: Mean frequency (133.6 bpm), Osc.- amplitude : (142 – 125.5= 16.5 bpm), Number of turning points (labelled with arrows): N= 61/Min
FETAL HEART FREQUENCY (bpm)
3
142
CTG-44180004.CTX
4
142 140 138 136 134
133.6
132 130 128
Turning point
126 32
33
34 35 36 TIME INTERVAL (Minutes)
37
38
39
4
Fig. 2 The fetal heart frequency is decreased during the last 30 min of delivery; this is predominantly due to the factor time itself and most probably not due to hypoxia and acidosis. Only more severe acidosis leads intermittently to episodes of bradycardia (cases with very high pH values (pH > 7.405, N = 3) were omitted).
The last 30 - Minutes of 481 fetuses with 14 430 CTG - Min ; red : 6.960≤ pH,UA
