Study and Validation of a Model
of Fetoplacental Circulation

2.5. Risultati delle prove di perfusione Results of the Perfusion Tests |
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Il presente capitolo raccoglie i risultati qualitativi e quantitativi delle prove di perfusione effettuate con sangue bovino, soluzione fisiologica e miscela di fissaggio.
I risultati quantitativi consistono, per i primi due tipi di perfusione, nei valori di pressione e portata ottenuti durante la sperimentazione, e, per quanto concerne il terzo fluido, nei dati morfometrici forniti dal dottor Gaetano Bulfamante, ricavati dall'esame anatomico delle placente fissate.

2.5. Results of the Perfusion Tests |
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This chapter resumes the results of the experiments of perfusion, with blood, isotonic solution and formaldehyde.
For the first 2 types of perfusion, the results are the values of flow and pressure measured; for the third method, they are the morphometric measurements performed by Dott. Gaetano Bulfamante during the dissection of the perfused placentas.

2.5.1. Perfusion Tests with Bovine Blood |
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Over 61 placentas, the experimentation has been fully achieved on 13, 4 of which coming from natural childbirth, during 49 work sessions at the hospital San Paolo of Milan.
The tables 10 to 22 summarize the results. The placentas that showed the presence of lacerations and/or stenoses have been rejected.

Portata di perfusione cc/min Flow | 80 |  | Sangue: Blood: |
Trasudamento % Seepage | -- |  | Ht | 31.5
Totale perdite % Leakages | 7.8 |  | PCO2 | 43.0
P arteriosammHg Arterial pressure | 150 |  | PO2 | 31.2
P venosammHg Venous pressure | 20 |  |  |

Tab.10: Placenta 1.

Portata di perfusione cc/min | 78-100 |  | Sangue: |
Trasudamento % | -- |  | Ht | 29.5
Totale perdite % | 29 |  | PCO2 | 37.0
P arteriosammHg | 80-205 |  | PO2 | 63.8
P venosammHg | 17-25 |  |  |

Tab.11: Placenta 2.

Portata di perfusione cc/min | 122 |  | Sangue: |
Trasudamento % | -- |  | Ht | 37.0
Totale perdite % | 41.6 |  | PCO2 | 38.0
P arteriosammHg | 93 |  | PO2 | 13.9
P venosammHg | 20 |  |  |

Tab.12: Placenta 3.

Portata di perfusione cc/min | 145 |  | Sangue: |
Trasudamento % | -- |  | Ht | 36.0
Totale perdite % | 31 |  | PCO2 | 66.4
P arteriosammHg | 76 |  | PO2 | 39.3
P venosammHg | 12 |  |  |

Tab.13: Placenta 4.

Portata di perfusione cc/min | 112 |  | Sangue: |
Trasudamento % | -- |  | Ht | 27.0
Totale perdite % | 1.8 |  | PCO2 | 84.5
P arteriosammHg | 120 |  | PO2 | 23.1
P venosammHg | 20 |  |  |

Tab.14: Placenta 5.

Portata di perfusione cc/min | 100 |  | Sangue: |
Trasudamento % | 16.9 |  | Ht | 34.0
Totale perdite % | 20 |  | PCO2 | 41.2
P arteriosammHg | 76 |  | PO2 | 27.8
P venosammHg | 15 |  |  |

Tab.15: Placenta 6.

Portata di perfusione cc/min | 145 |  | Sangue: |
Trasudamento % | -- |  | Ht | 38.0
Totale perdite % | 38 |  | PCO2 | 36.9
P arteriosammHg | 145 |  | PO2 | 13.8
P venosammHg | 21 |  |  |

Tab.16: Placenta 7.

Portata di perfusione cc/min | 213 |  | Sangue: |
Trasudamento % | 12.7 |  | Ht | 31.5
Totale perdite % | 31.9 |  | PCO2 | 15.2
P arteriosammHg | 104 |  | PO2 | 13.4
P venosammHg | 14 |  |  |

Tab.17: Placenta 8.

Portata di perfusione cc/min | 190 |  | Sangue: |
Trasudamento % | 18.3 |  | Ht | 36.0
Totale perdite % | 21.1 |  | PCO2 | 30.6
P arteriosammHg | 180 |  | PO2 | 28.2
P venosammHg | 19 |  |  |

Tab.18: Placenta 9.

Portata di perfusione cc/min | 145 |  | Sangue: |
Trasudamento % | -- |  | Ht | 26.0
Totale perdite % | 10.34 |  | PCO2 | 76.0
P arteriosammHg | 115 |  | PO2 | 16.0
P venosammHg | 20 |  |  |

Tab.19: Placenta 10.

Portata di perfusione cc/min | 210 |  | Sangue: |
Trasudamento % | 17.1 |  | Ht | 25.0
Totale perdite % | 42.2 |  | PCO2 | 35.5
P arteriosammHg | 181 |  | PO2 | 27.4
P venosammHg | 21 |  |  |

Tab.20: Placenta 11.

Portata di perfusione cc/min | 90 |  | Sangue: |
Trasudamento % | 46 |  | Ht | 37.0
Totale perdite % | 54.1 |  | PCO2 | 70.3
P arteriosammHg | 169 |  | PO2 | 29.0
P venosammHg | 16 |  |  |

Tab.21: Placenta 12.

Portata di perfusione cc/min | 145 |  | Sangue: |
Trasudamento % | 35.8 |  | Ht | 26.0
Totale perdite % | 37.8 |  | PCO2 | 51.2
P arteriosammHg | 180 |  | PO2 | 25.5
P venosammHg | 18 |  |  |

Tab.22: Placenta 13.

We executed also some tests injecting a dilator (Isoptin, of Knoll A.G., 1cc) into the placenta #5, obtaining appreciable variations of pressure:
Tab.23/A: placenta #5 (with Isoptin).
Tab.23/B: placenta #5 (as above, with higher flow).

Portata ingresso cc/min Input flow | 112
P arteriosa mmHg Arterial Pressure | 30
P venosa mmHgmmHg Venous Pressure | 20

Tab.23/A: Placenta #5 (with Isoptin).
.

Portata ingresso cc/min | 165
P arteriosa mmHg | 63
P venosa mmHg | 21

Tab.23/B: Placenta #5 (as above, with bigger flow).

These data confirm that the high pressure measured in the arterial cannulas is not due to formation of coagulates in the placenta during the incannulation.
The time of perfusion spans between 5 and 29 minutes. The seepage causes the elevation of the haematocrite of the blood beyond the physiological values, reason for which the test cannot be hold for greater times, unless we use a bigger reservoir.
In fact the arterial pressure, after some minutes of perfusion with blood, starts to increase, even if we attempt to contrast the phenomenon with Isoptin or higher partial pressure of CO2. In our opinion it is due to the increase of the viscosity of the blood, caused mainly by the increase of haematocrite. In fact the perfusion with isotonic solution at the same PCO2 of the blood of the umbilical arteries, even if hold beyond 20 minutes, does not give place to the described problem. Moreover the increase of viscosity influences the pressure due to the arterial cannulas: during the tests, increments of the order of 200 mmHg have been detected, such to cause obvious difficulties of determination of the effective arterial pressure.
The observed values of seepage of plasma (averaging 24,3% of the perfusion flow) confirm something that had already been discovered by other Dutch researchers [38] during experiments hold with isotonic solution rather than with blood.

2.5.2. Perfusion Tests with Formaldehyde |
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Six placentas have been perfused, 3 of which coming from natural childbirth.
During the preliminary perfusion with isotonic solution we measured the values of Tab 24.

Placenta | Weight g | Flow cc/min | Pressure Torr
2 | 410 | 235~ 265 | 48~ 55
3 | 850 | 225 | 35
4 | 640 | 168 | 33
5 | 620 | 190~ 265 | 22~ 40
6 | 690 | 145 | 70

Tab.24: Measurements carried out during the perfusion with isotonic solution.
The first placenta does not appear because it was perfused directly with formalin

The obtained values of pressure are lower than the ones recorded in literature [38]. We found a remarkable reactivity to the concentration of carbon dioxide in the perfusion fluid. During the first experiments, that were carried out without bubbling CO2 into the water, we always had an increment of the inlet pressure, at steady flow, such to produce lacerations. The increase started within 4 minutes from the beginning of the perfusion and reached the full scale of our instrument (360 Torr) in 3 to 7 more minutes.
What is known on the reactivity of the human placenta is derived from experiments of perfusion on placentas after the childbirth: we do not have quantitative data from the medical literature, and our aims did not include this type of study.
The transition from isotonic solution to fixation solution gives place to positive or negative not meaningful variations of the arterial pressure (lower than 10 Torr): the viscosity of the two fluids is similar and seems that they are not cause of reactions of constriction or expansion.
Table 25 and 26 summarize the perfusion data and the morphometric values obtained at the laboratory of Pathological Anatomy of the hospital San Paolo on the first two fixed placentas.

Placenta | Flow cc/min | Leakage cc/min | Perfusion time min
1 | 100 | 12.51 | 15
2 | 250 | 20.58 | 17
3 | 225 | 29.41 | 17
4 | 168 | 56.81 | 22
5 | 190 | 13.95 | 43
6 | 125 | 34.61 | 26

Tab.25: Measures carried out during the perfusion with fixation mix.
The leakages are total: effective leakages and seepage are not split.
.

Vessel order |  | Vein m m | Artery m m
Chorionic |  | 1185 | 1185
Trunci |  | 950 | 950
Rami | I | 1476 | 2208
| II | 1118 | 1417
| III | 296 | 710
| IV | 95 | 267
Ramuli |  | 59.7~ 190.3 | 59.7~ 190.3
V. term. e sinusoids |  | 13.94 | 13.94

Tab.26: Ranges of placental vessels obtained from the analysis at the microscope of two of the fixed placentas:
the field of the dimensions of the ramuli comprises all of the 10 orders of veins and arteries.

The first orders of vessels introduce two arteries for each vein. The physician who carried out the measurements supposes that the situation is presumably opposite starting from the rami.
He verified that the perfusion had been executed correctly, as the fixing fluid was been able to reach all the placental vessels up to the sinusoids.
Some microphotographies are evidence that our method of perfusion is useful to carry out the measurements of the placental vessels.

Fig.51: Stem villus (ramus, II or III order, with 3 main vessels) surrounded by terminal villi.
Magnification x180. Placenta not perfused.

Fig.52: As above, placenta perfused with fixing solution.

The figures 51 and 52 are related to the same the type of section of a not perfused placenta and of a perfused placenta. They evidence a remarkable difference: the not perfused villi appear constituted mainly by connective tissue, while as a result of perfusion they are quite more expanded. Data of table 26 better define the exposed concepts.

Fig.53: Stem villus (ramus of IV the order, the last one that has a muscular layer).
Section in resin, magnified x1150. Placenta not perfused.

Figures 53 and 54 allow a comparison between perfused and not perfused vessels pertaining to same the level.

Fig.54: Stem villus (ramus of IV order). Section in resin, magnified x1150.
Placenta perfused with fixing solution.

The sections in paraffin are 4 mm thick, the ones in resin approximately 1 mm.
The figure 55, related to a ramus of II order, reveals the usual vasoconstriction of the placenta after the childbirth: the section of vessels is filled by the connective tissue and by the muscular tissue of the vessels themselves.
The measurements carried out on the terminal villi of the perfused placentas did not evidence differences compared to data from the literature [20].

Fig.55: Stem villus (ramus of II order). Section in resin, magnified x460.
Placenta not perfused.

Fig.56: Terminal villus. Section in resin, magnified x1800.
Placenta not perfused.

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