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The respiratory gas values of the fetal and maternal blood in cartesian nomograms
Respiration
THE
Physiology
RESPIRATORY
(1966) 1,366-37 1; North-Holland
GAS
BLOOD
VALUES
OF THE
IN CARTESIAN
Publishing
Company,
FETAL
AND
Amsterdam
MATERNAL
NOMOGRAMS
W. M. FISCHER, G. THEWS AND H. R. VOGEL Department
of Physiology,
University
of Mainr,
Germany
Abstract. Respiratory gas values of maternal and fetal blood taken at delivery are represented in two Cartesian nomograms. They are based on data, published by VOGEL,FISCHERund THEWS(1965) and
FISCHER,VOGELund THEWS(1965). The nomograms depict the interdependence of 02 pressure, 02 content, CO2 pressure and CO2 content, established by the 02 and COZ dissociation curves, as well as by the Bohr effect and the Haldane effect. If two of the values are known, the remaining ones can be read from the nomograms. Fetus blood Maternal blood
Placental gas exchange OZ-COZ diagram
The gas exchange in the placenta is decisively influenced by the 0, and CO, affinity of the fetal and maternal blood. When examining placental exchange conditions, knowledge of both the 0, and CO2 dissociation curves, as well as of their dependence on different parameters is required. The Bohr effect determines the influence of the CO2 pressure on the 0, content; the Haldane effect that of the 0, saturation and consequently, indirectly that of the 0, pressure on the CO, content. Through this interdependence a relationship between 0, content, 0, pressure, CO2 content and CO2 pressure is established, which can be represented in the form of Cartesian nomograms. A nomogram of this type, such as was established by RAHN and FENN (1955) for the blood of the healthy adult and by EDWARDS and Ross (1959) for the fetal and maternal blood, is of great help in evaluating the transport function of the blood for the respiratory gases, as well as the analysis of the exchange processes. Basis for the nomograms The basis for the nomograms presented is formed by the complete pH- or CO,dependent O2 dissociation curves (VOGEL, FISCHER and THEWS, 1965), determined in 41 cases for both mother and fetus, as well as by the complete 0, saturation-dependent CO, dissociation curves, determined in 54 cases (FISCHER, VOGEL and THEWS, 1965). Accepted
for publication
3 May
1966.
366
367
RESPIRATORY GASES IN FETAL AND MATERNAL BLOOD
Maternal
and fetal blood samples were taken simultaneously
Taking the mean values of 12.0 g% and and 16.3 meq/l and 16.0 meq/l standard
at the moment
of birth.
16.0 g% for the hemoglobin concentration bicarbonate concentration of maternal and
fetal blood into account, pairs of values for the 0, and CO, contents belonging to those given for the 0, and CO2 pressures were then selected from the sets of curves. Results The values obtained
can be represented
in Cartesian
nomograms
in two ways.
PO*-Pco2 NOMOGRAMS If the 0, pressures are plotted on the abscissa, and the CO1 pressures on the ordinate of the nomogram, the pertinent O2 and CO2 contents then form the parameters of two intersecting sets of curves. This form of representation was chosen for the maternal blood in fig. 1 and for the fetal blood in fig. 2. It is particularly suitable for determining the gas concentrations from given gas pressures. For example, if the mean 0, pressure
Fig. 1.
measured by us in the v. umbilicalis, at the very moment of delivery, is 22.4 mm Hg, and the mean CO, pressure 42.0 mm Hg, the pertinent values for the 0, and CO, contents are then read from fig. 1 as 9.8 and 34.2 vol %.
368
W. M. FISCHER, G. THEWS
AND
H. R. VOCiEL
co2-Go2NOMOGRAMS The second way is to consider the 0, and CO2 contents as coordinate values, and the 0, and CO2 pressures as parameters. This produces the sets of curves plotted in fig. 3 and fig. 4. This method of representation is particularly suitable for establishing a connection with the respiratory exchange ratio, R, as here the curves of the same R-value are straight lines. At the end of pregnancy. the maternal arterial blood contains an average of 15.4 vol “/, O2 and 27.6 vol % C02, while for the venous blood of the a. umbilicalis, which also flows into the placenla, mean concentrations of 2.4 vol 7; 0, and 41.1 vol % CO, are given (VOGEL PI crl,, 1965; FISCHER et al., 1965). The R-lines in figs. 3 and 4 were plotted, beginning at these two points. At the end of pregnancy the metabolic respiratory exchange ratio comes to about 0.92. This
Fig. 2. Cartesian Po,-Pco,-nomogram for the respiratory gas values of the fetal blood at the moment of delivery. Abscissa: 02 pressure (PoJ. Ordinate: CO2 pressure (Pco,). Parameters: 02 concentration Kk,) and CO2 concentration (C,O,).
knowledge enables us to derive the three remaining values from fig. 4 after measuring only one partial pressure or gas concentration in the v. umbiiicahs. For example, if PO, = 22.4 mm Hg, the values Pco, = 42 mm Hg, Co, = 9.8 vol % and Go, = 34.2
RESPIRATORY GASES IN FETAL AND MATERNALBLOOD
369
251 0
Fig. 3. Cartesian Co,-Go,-nomogram for the respiratory gas values of the maternal blood at the moment of delivery. Abscissa: 02 concentration (Co,). Ordinate: COZ concentration (&I,). Parameters: 02 pressure (PO,), CO2 pressure (Pco,) and respiratory exchange ratio, R, (dotted lines). The R-lines begin at the values of the maternal arterial blood (Co, = 15.4 vol %; Cco, = 27.6 v01 %. vol 'A are read from the intersection
regionally
varying
respiratory
with R = 0.92. From fig. 4 it is evident that the exchange ratio can never fall below R = 0.24 or exceed
R = 9.0, whatever the exchange conditions. Because the venous CO, pressure of the fetal blood found in the a. umbilicalis after the exchange can never be exceeded, and no pressure can be lower than that of the venous 0, pressure, the regional R-values are restricted to the area plotted in the figure. This restriction is a result of the Haldane effect and the Bohr effect (FENN, RAHN and OTIS, 1946; HERTZ, 1957; HERTZ, THEWS and SCHMIDT, 1965). The special exchange conditions of a multivillous stream-system, found in the human placenta, lead to a further limitation of the possible variation for the respiratory exchange ratio. Discussion Similar nomograms, previously published by EDWARDS and ROSS (1959), used values obtained from maternal blood taken 3 weeks prior to delivery and from fetal blood
370
W. M. FISCHER, G. THEWS AND H. R. VOGEL
Ccc pkll %
_
I
25.
Fig. 4. Cartesian Co,-Cco,-nomogram for the respiratory gas values of the fetal blood at the moment of delivery. Abscissa: 0s concentration (CO,). Ordinate: COZ concentration (CCOJ. Parameters: 0~ pressure (PO,), CO2 pressure (Pco,) and respiratory exchange ratio, R, (dotted lines). The R-lines begin at the values of the fetal venous blood (Co, = 2.4 vol %; Cco, = 41.1 vol %).
taken after Cesarean sections, as well as after normal deliveries. The collection of blood samples at different times ante partum may account for the high CO, contents found by the authors. Use of the nomograms for evaluating gas exchange in the placenta presupposes their validity for the same interval of time. This prerequisite is reasonably satisfied by the simultaneous collection of blood samples. Our values were obtained from blood samples taken simultaneously at the time of birth. An extensive comparison of our values and previously obtained data may be found in the papers of VOGEL et al. (1965) and FISCHER et al. (1965). Finally it should be mentioned that the validity of our nomograms is dependent upon the following values for O2 capacity and standard bicarbonate concentration: 0, capacity: maternal blood: 16.1 vol % (&- 1.8 SD); fetal blood: 21.4 vol % (+ 1.4
RESPIRATORY
GASES IN FETAL
SD); standard bicarbonate concentration: fetal blood: 16.0 meq/l (k2.9 SD).
AND MATERNAL
BLOOD
maternal blood: 16.3 meq/l (22.2
371
SD);
References EDWARDS, M. J. and B. B. Ross (1959). Graphical representation of respiratory gas dissociation characteristics of fetal and maternal blood. J. Appl. Physiol. 14: 454456. FENN, W. O., H. RAHN and A. B. OTIS (1946). A theoretical study of the composition of the alveolar air at altitude. Am. J. Physiol. 146: 637-653. FISCHER,W. M., H. R. VOGELund G. THEWS(1965). Der Slure-Basenstatus und die COz-Transportfunktion des miitterlichen und fetalen Blutes zum Zeitpunkt der Geburt. PJ?iigers Arch. Ges. Physiol. 286: 220-237.
HERTZ, C. W. (1957). Stiirungen der Ventilation. In: Lunge und kleiner Kreislauf. Oeynhausener Gesprgche I: 127-143, Springer, Berlin-GGttingen-Heidelberg. HERTZ, C. W., G. THEWSund K. SCHMIDT(1965). Verteilung der Ventilations-Perfusionsrelation beim Lungenemphysem. Klin. Wochschr. 43 : 1187-l 193. RAHN, H. and W. 0. FENN (1955). A graphical analysis of the respiratory gas exchange. Washington, D.C. : Amer. Physiol. Sot. VOGEL,H. R., W. M. FISCHERund G. THEWS(1965). Die Oz-Transportfunktion des miitterlichen und fetalen Blutes zum Zeitpunkt der Geburt. Ppigers Arch. Ges. Physiol. 286: 238-250.
THE
Physiology
RESPIRATORY
(1966) 1,366-37 1; North-Holland
GAS
BLOOD
VALUES
OF THE
IN CARTESIAN
Publishing
Company,
FETAL
AND
Amsterdam
MATERNAL
NOMOGRAMS
W. M. FISCHER, G. THEWS AND H. R. VOGEL Department
of Physiology,
University
of Mainr,
Germany
Abstract. Respiratory gas values of maternal and fetal blood taken at delivery are represented in two Cartesian nomograms. They are based on data, published by VOGEL,FISCHERund THEWS(1965) and
FISCHER,VOGELund THEWS(1965). The nomograms depict the interdependence of 02 pressure, 02 content, CO2 pressure and CO2 content, established by the 02 and COZ dissociation curves, as well as by the Bohr effect and the Haldane effect. If two of the values are known, the remaining ones can be read from the nomograms. Fetus blood Maternal blood
Placental gas exchange OZ-COZ diagram
The gas exchange in the placenta is decisively influenced by the 0, and CO, affinity of the fetal and maternal blood. When examining placental exchange conditions, knowledge of both the 0, and CO2 dissociation curves, as well as of their dependence on different parameters is required. The Bohr effect determines the influence of the CO2 pressure on the 0, content; the Haldane effect that of the 0, saturation and consequently, indirectly that of the 0, pressure on the CO, content. Through this interdependence a relationship between 0, content, 0, pressure, CO2 content and CO2 pressure is established, which can be represented in the form of Cartesian nomograms. A nomogram of this type, such as was established by RAHN and FENN (1955) for the blood of the healthy adult and by EDWARDS and Ross (1959) for the fetal and maternal blood, is of great help in evaluating the transport function of the blood for the respiratory gases, as well as the analysis of the exchange processes. Basis for the nomograms The basis for the nomograms presented is formed by the complete pH- or CO,dependent O2 dissociation curves (VOGEL, FISCHER and THEWS, 1965), determined in 41 cases for both mother and fetus, as well as by the complete 0, saturation-dependent CO, dissociation curves, determined in 54 cases (FISCHER, VOGEL and THEWS, 1965). Accepted
for publication
3 May
1966.
366
367
RESPIRATORY GASES IN FETAL AND MATERNAL BLOOD
Maternal
and fetal blood samples were taken simultaneously
Taking the mean values of 12.0 g% and and 16.3 meq/l and 16.0 meq/l standard
at the moment
of birth.
16.0 g% for the hemoglobin concentration bicarbonate concentration of maternal and
fetal blood into account, pairs of values for the 0, and CO, contents belonging to those given for the 0, and CO2 pressures were then selected from the sets of curves. Results The values obtained
can be represented
in Cartesian
nomograms
in two ways.
PO*-Pco2 NOMOGRAMS If the 0, pressures are plotted on the abscissa, and the CO1 pressures on the ordinate of the nomogram, the pertinent O2 and CO2 contents then form the parameters of two intersecting sets of curves. This form of representation was chosen for the maternal blood in fig. 1 and for the fetal blood in fig. 2. It is particularly suitable for determining the gas concentrations from given gas pressures. For example, if the mean 0, pressure
Fig. 1.
measured by us in the v. umbilicalis, at the very moment of delivery, is 22.4 mm Hg, and the mean CO, pressure 42.0 mm Hg, the pertinent values for the 0, and CO, contents are then read from fig. 1 as 9.8 and 34.2 vol %.
368
W. M. FISCHER, G. THEWS
AND
H. R. VOCiEL
co2-Go2NOMOGRAMS The second way is to consider the 0, and CO2 contents as coordinate values, and the 0, and CO2 pressures as parameters. This produces the sets of curves plotted in fig. 3 and fig. 4. This method of representation is particularly suitable for establishing a connection with the respiratory exchange ratio, R, as here the curves of the same R-value are straight lines. At the end of pregnancy. the maternal arterial blood contains an average of 15.4 vol “/, O2 and 27.6 vol % C02, while for the venous blood of the a. umbilicalis, which also flows into the placenla, mean concentrations of 2.4 vol 7; 0, and 41.1 vol % CO, are given (VOGEL PI crl,, 1965; FISCHER et al., 1965). The R-lines in figs. 3 and 4 were plotted, beginning at these two points. At the end of pregnancy the metabolic respiratory exchange ratio comes to about 0.92. This
Fig. 2. Cartesian Po,-Pco,-nomogram for the respiratory gas values of the fetal blood at the moment of delivery. Abscissa: 02 pressure (PoJ. Ordinate: CO2 pressure (Pco,). Parameters: 02 concentration Kk,) and CO2 concentration (C,O,).
knowledge enables us to derive the three remaining values from fig. 4 after measuring only one partial pressure or gas concentration in the v. umbiiicahs. For example, if PO, = 22.4 mm Hg, the values Pco, = 42 mm Hg, Co, = 9.8 vol % and Go, = 34.2
RESPIRATORY GASES IN FETAL AND MATERNALBLOOD
369
251 0
Fig. 3. Cartesian Co,-Go,-nomogram for the respiratory gas values of the maternal blood at the moment of delivery. Abscissa: 02 concentration (Co,). Ordinate: COZ concentration (&I,). Parameters: 02 pressure (PO,), CO2 pressure (Pco,) and respiratory exchange ratio, R, (dotted lines). The R-lines begin at the values of the maternal arterial blood (Co, = 15.4 vol %; Cco, = 27.6 v01 %. vol 'A are read from the intersection
regionally
varying
respiratory
with R = 0.92. From fig. 4 it is evident that the exchange ratio can never fall below R = 0.24 or exceed
R = 9.0, whatever the exchange conditions. Because the venous CO, pressure of the fetal blood found in the a. umbilicalis after the exchange can never be exceeded, and no pressure can be lower than that of the venous 0, pressure, the regional R-values are restricted to the area plotted in the figure. This restriction is a result of the Haldane effect and the Bohr effect (FENN, RAHN and OTIS, 1946; HERTZ, 1957; HERTZ, THEWS and SCHMIDT, 1965). The special exchange conditions of a multivillous stream-system, found in the human placenta, lead to a further limitation of the possible variation for the respiratory exchange ratio. Discussion Similar nomograms, previously published by EDWARDS and ROSS (1959), used values obtained from maternal blood taken 3 weeks prior to delivery and from fetal blood
370
W. M. FISCHER, G. THEWS AND H. R. VOGEL
Ccc pkll %
_
I
25.
Fig. 4. Cartesian Co,-Cco,-nomogram for the respiratory gas values of the fetal blood at the moment of delivery. Abscissa: 0s concentration (CO,). Ordinate: COZ concentration (CCOJ. Parameters: 0~ pressure (PO,), CO2 pressure (Pco,) and respiratory exchange ratio, R, (dotted lines). The R-lines begin at the values of the fetal venous blood (Co, = 2.4 vol %; Cco, = 41.1 vol %).
taken after Cesarean sections, as well as after normal deliveries. The collection of blood samples at different times ante partum may account for the high CO, contents found by the authors. Use of the nomograms for evaluating gas exchange in the placenta presupposes their validity for the same interval of time. This prerequisite is reasonably satisfied by the simultaneous collection of blood samples. Our values were obtained from blood samples taken simultaneously at the time of birth. An extensive comparison of our values and previously obtained data may be found in the papers of VOGEL et al. (1965) and FISCHER et al. (1965). Finally it should be mentioned that the validity of our nomograms is dependent upon the following values for O2 capacity and standard bicarbonate concentration: 0, capacity: maternal blood: 16.1 vol % (&- 1.8 SD); fetal blood: 21.4 vol % (+ 1.4
RESPIRATORY
GASES IN FETAL
SD); standard bicarbonate concentration: fetal blood: 16.0 meq/l (k2.9 SD).
AND MATERNAL
BLOOD
maternal blood: 16.3 meq/l (22.2
371
SD);
References EDWARDS, M. J. and B. B. Ross (1959). Graphical representation of respiratory gas dissociation characteristics of fetal and maternal blood. J. Appl. Physiol. 14: 454456. FENN, W. O., H. RAHN and A. B. OTIS (1946). A theoretical study of the composition of the alveolar air at altitude. Am. J. Physiol. 146: 637-653. FISCHER,W. M., H. R. VOGELund G. THEWS(1965). Der Slure-Basenstatus und die COz-Transportfunktion des miitterlichen und fetalen Blutes zum Zeitpunkt der Geburt. PJ?iigers Arch. Ges. Physiol. 286: 220-237.
HERTZ, C. W. (1957). Stiirungen der Ventilation. In: Lunge und kleiner Kreislauf. Oeynhausener Gesprgche I: 127-143, Springer, Berlin-GGttingen-Heidelberg. HERTZ, C. W., G. THEWSund K. SCHMIDT(1965). Verteilung der Ventilations-Perfusionsrelation beim Lungenemphysem. Klin. Wochschr. 43 : 1187-l 193. RAHN, H. and W. 0. FENN (1955). A graphical analysis of the respiratory gas exchange. Washington, D.C. : Amer. Physiol. Sot. VOGEL,H. R., W. M. FISCHERund G. THEWS(1965). Die Oz-Transportfunktion des miitterlichen und fetalen Blutes zum Zeitpunkt der Geburt. Ppigers Arch. Ges. Physiol. 286: 238-250.