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Factors Influencing the Pressure-Flow-Perfusion System
C:022-5347 /82/i2~;5-l02lS02.CO/J TEE JouRKAL OF UROLOGY
Copyright© 1982
?he WiJlian'IB & Viilkins Co.
THE ALLAN G. TOGURI*
AND
GEORGE FOURNIER
From the Division of Urology, University o/ Texas _Medical Branch, Galveston, Texas
ABSTRACT
The methodology of the "Pressure-Flow-Perfusion System" used in the "Whitaker Test" was examined for factors which influence intrinsic resistance of that system. Considerable pressure changes were incurred by varying the concentration of sodium diatrizoate, perfusing needle, temperature and flow rates. For each renal pressure-flow-perfusion test, the resistance nmst be determined because of the effect of each variable in altering the intrinsic resistance. The renal pressure-flow-perfusion test, although simply performed, involves complex physicochemical concepts applied to a multicompartmental biologic and nonbiologic system. The purpose of this paper is to present some of the nonbiologic considerations to emphasize the need to define and standardize the methodology used so that the results obtained can be interpreted intelligently. The basic principle of the pressure-flow-perfusion test is based on a steady state condition which means that an equilibrium exists between the constant flow into and out of the system at a particular pressure and temperature (fig. 1, A). A cause (such as an obstruction or a diuresis) which alters this state would be manifested as a pressure change. The Whitaker Test 1 is based on this principle. It differs in many ways, however, one of which we consider in this paper. The pressure measured (fig. l, B) is outside the compartment assumed to be in equilibrium. The pressure recorded is the sum of all the resistances (pressure) in the nonbiologic and biologic systems assumed in equilibrium when flow in is equal to the flow out (fig. 1, It is necessary to know the infusion pressure "Ri'' (resistance to flow of the nonbiologic compartment) in order to calculate the renal pressure "Rk" (or simply (Rk = R1 - (Rb+ Ru)). The recorded pressure is affected by rnany known nonbiologic factors as the nature of the perfusion as well as the physicochemical characteristics of the perfusing fluid. MATERIALS AND METHODS
The major variables of the nonbiologic pressure-flow perfusion system were assessed individually to determine the effect on intrinsic resistance (R,) of the infusion To assure that the pert11s1on circuit stant infusion from a screw Insh·ument model #975), the water delivered (room per unit time was determined and to the manufacturer's stated flow rates (table 1). To show the effect of different concentrations of sodium diatrizoate were studied. This a radiodense u~·,::,·,,,·::,'~,,"c"n'~~u'" which is viscous. The '11'U'f1,Qlt'1 was altered dilution and by increasing temperature. The viscosity of 6.25 per cent, 12.5 per cent, and 25 per cent sodium diatrizoate was measured at temperatures of 25C, 37C, and 42C (fig. 3), with Fischer-Scientific Viscometer Type R+ #357, size 25. The methods used are in accordance to ASTM standards with temperature equilibration time of 10 minutes and (test) volume of 10 ml. To show the effect of this viscosity on the recorded pressure, circuit "A" was used. The varying concentrations of sodium diatrizoate were pumped at constant flow rates of 5.9, 8.3 and 11.5 ml,/minute through 18-gauge needles 9 cm. and 3.9 cm. long (fig. 4, A and B), and the intrinsic resistance or viscous
drag was recorded in the described pressure recording system. The changes in intrinsic resistance of the pressu:re-flow-perfusion system were examined by varying the nonbiologic components. The different variable were: 1) pv,e
PRINCIPLE
WHITAKER
F
LJ-·
ACTUAL
FIG. l. Diagram of of the system; F 0 = Flow non-biologic infusion system;
Accepted for publication October 12, 1981. * Requests for reprints: Department of Urology, Kingston General Hospital, Queen's University, Kingston, Ontario K7L 2V7, Canada.
1021
A
Extension set
T
Transducer
C
Water column
~
Needle
lldh
Stop-cock FIG. 2. Diagram of perfusion circuit.
1022
TOGURI AND FOURNIER
TABLE
VARIABLES: INFUSION-PRESSURE (22°C CIRCUIT A)
1. Volume of water delivered per unit time compared to
manufacturer's stated flow rates* Pump Setting 5
5 6 6
7 7 8 8 9 9
10 10 11 11
Observed Flow (ml./min.)
Stated Flow (ml./min.)
Difference (ml./min.)
11.25 11.50 8.18 8.31 6.00 5.90 4.19 4.22 3.00 3.00 2.16 2.16 1.51 1.50
12.1 12.1 8.64 8.64 6.17 6.17 4.41 4.41 3.15 3.15 2.25 2.25 1.61 1.61
0.85 0.6 0.5 0.3 0.17 0.27 0.22 0.19 0.15 0.15 0.09 0.09 0.10 0.10
60 0 I
N
s
50
TYPE OF NEEDLE
40
18 G; 3.8 cm
30
11.5 ml/min
20
8.3 ml/min 5.9 ml/min
10
* System used: Circuit A with 50-ml. glass syringe (#1502) with water as perfusate.
6.25 12.5
25
50
% CONCENTRATION
2.0
-
VARIABLES: INFUSION - PRESSURE (22°C CIRCUIT A)
( .)
(l)
Cl)
'N E 1.4
->I-
(/)
0
u (/)
>
O 25°C
1.2 1.0 0.8 0.6
0 0
0 A
D A
0 50
o
0
0
60 N
37°C
::i:::
A 42°C
E C.)
A
40
11.5 ml/min TYPE OF NEEDLE
18 G; 9 cm 8.3 ml/min
30
5.9 ml/min
20 10 6.25 12.5
25
50
% CONCENTRATION
6.25
12.5
25
FIG. 4. Concentrations of sodium diatrizoate pumped at constant flow rates. A, through an 18-gauge 3.8 cm. needle. B, through an 18gauge, 9 cm. needle.
% CONCENTRATION FIG. 3. Viscosity expressed in terms of Kinematic Viscosity Coherent Units.
manometer. The transducer itself was checked for linearity prior to testing and was accurate to ±0.5 cm. H20. The recording system used was a 4-channel Life Tech chart recorder. To obtain baseline studies for percutaneous studies, circuit "B" was used with a 100-ml. glass syringe (#9977) and a concentration of sodium diatrizoate of 25 per cent. This was perfused at room temperature at varying constant flow rates through an 18 gauge 9 cm. spinal needle and through an 18gauge 3.5 cm. needle, and the intrinsic resistances (pressure) (fig. 5) were measured as previously described. RESULTS
Table 1 shows that the constant infusion pump delivered the perfusate with a maximum 7 per cent difference of the stated flow rates. Figure 3 shows the effect of concentration of contrast agent and temperature. Figure 4 shows the effect of viscous drag as manifested by the recorded pressure, at room temperature.
Table 2 shows the difference in intrinsic pressure caused by using: 1) different length 18-gauge needles, 2) different length perfusion circuits A and B, 3) different perfusate, and 4) different constant flow rates; all at a constant temperature of 22C. Figure 5 shows the pressure flow variations to be linear. DISCUSSION
The least variable compartment of the renal pressure-flowperfusion system was examined to see how the recorded pressure of the Whitaker Test is affected by the nonbiologic components of the test system. It was observed in table 2 that the pressure could be altered considerably by altering the variables of needle, flow rate and perfusate in the nonbiologic compartment. The pressure recorded from this compartment represents the viscous drag or intrinsic pressure of the perfusion system. Since this pressure can be altered by the variables examined, the methodology should be standardized in each laboratory and the intrinsic pressure recorded for each test. This is essential since the renal pelvic pressure is determined indirectly by subtracting the pressures for each compartment from this intrinsic pressure.
1-023 0
30
'TABLE
Needle 18-gauge, 9 cm.
25 0
ffi
~
20
D
25% HYPAQUE
22°C
~ E 15 t.)
18-gauge, 3.8 cm. D
10
2
Constant Flow (ml./ min.)
Perfusate*
11.5 11.5 8.3 8.3 5.9 5.9
W. H. W. H. W. H.
11.5 11.5
W. H.
TDt Pressure (cm H 20)
B-A Pressure Difference
A
B
14.0 23.0 10.0
16.0 27.0 11.0
2.0 4.0
16.0 7.0 11.0
19.C
3.0
7.5 14.0
0.5 3.0
10.0 17.0 7.0 11.5 5.0 8.0
2.0 5.0 LO 3.0 LO 2.0
1.0
0
0
8 6 4
2. Alteration of iritrinsic resistance by variables
D 0 NEEDLE GAUGES
0
0 18 G -
0 0
9cm
D 18 G -J.Bcm
W.
H. W. H.
4.0
6.0
* W = water; H = 25 per cent diatrizoate sodium.
t Transducer Pressure: A = circuit A; B = circuit B.
D
0
D
0
8.3
8.3 5.9 5.9
8.0
12.0 6.0 8.5
0
2
3
4
5
6
7
8
9
10 11 12 13 14
ml/min
Fm. 5. Pressure flow variation.
The viscous drag is the largest resistance in the multicompartment system of which the nonbiologic compartment variables can be controlled as shown in table 2. Few assumptions are made in obtaining the pressure-flow-perfusion data as compared to the biologic compartment where even under the best of circumstances pressure-flow variations require fluoroscopy
for reasonable interpretation. It is emphasized that care be taken to standardize the methodology of the renal pressure-flow-perfusion test to minimize the controllable variations due to needle, perfusion fluid, temperature and flow rate. REFERENCES 1. Whitaker, R. H.: Diagnosis of obstruction in dilated ureters. Ann.
Roy. Coll. Surg. Engl., 53: 153, 1973. 2. Diem, K. and Lentner, C.: Documenta Geigy Scientific Tables. Basel: J. R. Geigy S. A., ed. 7, p. 214, 1970.
Copyright© 1982
?he WiJlian'IB & Viilkins Co.
THE ALLAN G. TOGURI*
AND
GEORGE FOURNIER
From the Division of Urology, University o/ Texas _Medical Branch, Galveston, Texas
ABSTRACT
The methodology of the "Pressure-Flow-Perfusion System" used in the "Whitaker Test" was examined for factors which influence intrinsic resistance of that system. Considerable pressure changes were incurred by varying the concentration of sodium diatrizoate, perfusing needle, temperature and flow rates. For each renal pressure-flow-perfusion test, the resistance nmst be determined because of the effect of each variable in altering the intrinsic resistance. The renal pressure-flow-perfusion test, although simply performed, involves complex physicochemical concepts applied to a multicompartmental biologic and nonbiologic system. The purpose of this paper is to present some of the nonbiologic considerations to emphasize the need to define and standardize the methodology used so that the results obtained can be interpreted intelligently. The basic principle of the pressure-flow-perfusion test is based on a steady state condition which means that an equilibrium exists between the constant flow into and out of the system at a particular pressure and temperature (fig. 1, A). A cause (such as an obstruction or a diuresis) which alters this state would be manifested as a pressure change. The Whitaker Test 1 is based on this principle. It differs in many ways, however, one of which we consider in this paper. The pressure measured (fig. l, B) is outside the compartment assumed to be in equilibrium. The pressure recorded is the sum of all the resistances (pressure) in the nonbiologic and biologic systems assumed in equilibrium when flow in is equal to the flow out (fig. 1, It is necessary to know the infusion pressure "Ri'' (resistance to flow of the nonbiologic compartment) in order to calculate the renal pressure "Rk" (or simply (Rk = R1 - (Rb+ Ru)). The recorded pressure is affected by rnany known nonbiologic factors as the nature of the perfusion as well as the physicochemical characteristics of the perfusing fluid. MATERIALS AND METHODS
The major variables of the nonbiologic pressure-flow perfusion system were assessed individually to determine the effect on intrinsic resistance (R,) of the infusion To assure that the pert11s1on circuit stant infusion from a screw Insh·ument model #975), the water delivered (room per unit time was determined and to the manufacturer's stated flow rates (table 1). To show the effect of different concentrations of sodium diatrizoate were studied. This a radiodense u~·,::,·,,,·::,'~,,"c"n'~~u'" which is viscous. The '11'U'f1,Qlt'1 was altered dilution and by increasing temperature. The viscosity of 6.25 per cent, 12.5 per cent, and 25 per cent sodium diatrizoate was measured at temperatures of 25C, 37C, and 42C (fig. 3), with Fischer-Scientific Viscometer Type R+ #357, size 25. The methods used are in accordance to ASTM standards with temperature equilibration time of 10 minutes and (test) volume of 10 ml. To show the effect of this viscosity on the recorded pressure, circuit "A" was used. The varying concentrations of sodium diatrizoate were pumped at constant flow rates of 5.9, 8.3 and 11.5 ml,/minute through 18-gauge needles 9 cm. and 3.9 cm. long (fig. 4, A and B), and the intrinsic resistance or viscous
drag was recorded in the described pressure recording system. The changes in intrinsic resistance of the pressu:re-flow-perfusion system were examined by varying the nonbiologic components. The different variable were: 1) pv,e
PRINCIPLE
WHITAKER
F
LJ-·
ACTUAL
FIG. l. Diagram of of the system; F 0 = Flow non-biologic infusion system;
Accepted for publication October 12, 1981. * Requests for reprints: Department of Urology, Kingston General Hospital, Queen's University, Kingston, Ontario K7L 2V7, Canada.
1021
A
Extension set
T
Transducer
C
Water column
~
Needle
lldh
Stop-cock FIG. 2. Diagram of perfusion circuit.
1022
TOGURI AND FOURNIER
TABLE
VARIABLES: INFUSION-PRESSURE (22°C CIRCUIT A)
1. Volume of water delivered per unit time compared to
manufacturer's stated flow rates* Pump Setting 5
5 6 6
7 7 8 8 9 9
10 10 11 11
Observed Flow (ml./min.)
Stated Flow (ml./min.)
Difference (ml./min.)
11.25 11.50 8.18 8.31 6.00 5.90 4.19 4.22 3.00 3.00 2.16 2.16 1.51 1.50
12.1 12.1 8.64 8.64 6.17 6.17 4.41 4.41 3.15 3.15 2.25 2.25 1.61 1.61
0.85 0.6 0.5 0.3 0.17 0.27 0.22 0.19 0.15 0.15 0.09 0.09 0.10 0.10
60 0 I
N
s
50
TYPE OF NEEDLE
40
18 G; 3.8 cm
30
11.5 ml/min
20
8.3 ml/min 5.9 ml/min
10
* System used: Circuit A with 50-ml. glass syringe (#1502) with water as perfusate.
6.25 12.5
25
50
% CONCENTRATION
2.0
-
VARIABLES: INFUSION - PRESSURE (22°C CIRCUIT A)
( .)
(l)
Cl)
'N E 1.4
->I-
(/)
0
u (/)
>
O 25°C
1.2 1.0 0.8 0.6
0 0
0 A
D A
0 50
o
0
0
60 N
37°C
::i:::
A 42°C
E C.)
A
40
11.5 ml/min TYPE OF NEEDLE
18 G; 9 cm 8.3 ml/min
30
5.9 ml/min
20 10 6.25 12.5
25
50
% CONCENTRATION
6.25
12.5
25
FIG. 4. Concentrations of sodium diatrizoate pumped at constant flow rates. A, through an 18-gauge 3.8 cm. needle. B, through an 18gauge, 9 cm. needle.
% CONCENTRATION FIG. 3. Viscosity expressed in terms of Kinematic Viscosity Coherent Units.
manometer. The transducer itself was checked for linearity prior to testing and was accurate to ±0.5 cm. H20. The recording system used was a 4-channel Life Tech chart recorder. To obtain baseline studies for percutaneous studies, circuit "B" was used with a 100-ml. glass syringe (#9977) and a concentration of sodium diatrizoate of 25 per cent. This was perfused at room temperature at varying constant flow rates through an 18 gauge 9 cm. spinal needle and through an 18gauge 3.5 cm. needle, and the intrinsic resistances (pressure) (fig. 5) were measured as previously described. RESULTS
Table 1 shows that the constant infusion pump delivered the perfusate with a maximum 7 per cent difference of the stated flow rates. Figure 3 shows the effect of concentration of contrast agent and temperature. Figure 4 shows the effect of viscous drag as manifested by the recorded pressure, at room temperature.
Table 2 shows the difference in intrinsic pressure caused by using: 1) different length 18-gauge needles, 2) different length perfusion circuits A and B, 3) different perfusate, and 4) different constant flow rates; all at a constant temperature of 22C. Figure 5 shows the pressure flow variations to be linear. DISCUSSION
The least variable compartment of the renal pressure-flowperfusion system was examined to see how the recorded pressure of the Whitaker Test is affected by the nonbiologic components of the test system. It was observed in table 2 that the pressure could be altered considerably by altering the variables of needle, flow rate and perfusate in the nonbiologic compartment. The pressure recorded from this compartment represents the viscous drag or intrinsic pressure of the perfusion system. Since this pressure can be altered by the variables examined, the methodology should be standardized in each laboratory and the intrinsic pressure recorded for each test. This is essential since the renal pelvic pressure is determined indirectly by subtracting the pressures for each compartment from this intrinsic pressure.
1-023 0
30
'TABLE
Needle 18-gauge, 9 cm.
25 0
ffi
~
20
D
25% HYPAQUE
22°C
~ E 15 t.)
18-gauge, 3.8 cm. D
10
2
Constant Flow (ml./ min.)
Perfusate*
11.5 11.5 8.3 8.3 5.9 5.9
W. H. W. H. W. H.
11.5 11.5
W. H.
TDt Pressure (cm H 20)
B-A Pressure Difference
A
B
14.0 23.0 10.0
16.0 27.0 11.0
2.0 4.0
16.0 7.0 11.0
19.C
3.0
7.5 14.0
0.5 3.0
10.0 17.0 7.0 11.5 5.0 8.0
2.0 5.0 LO 3.0 LO 2.0
1.0
0
0
8 6 4
2. Alteration of iritrinsic resistance by variables
D 0 NEEDLE GAUGES
0
0 18 G -
0 0
9cm
D 18 G -J.Bcm
W.
H. W. H.
4.0
6.0
* W = water; H = 25 per cent diatrizoate sodium.
t Transducer Pressure: A = circuit A; B = circuit B.
D
0
D
0
8.3
8.3 5.9 5.9
8.0
12.0 6.0 8.5
0
2
3
4
5
6
7
8
9
10 11 12 13 14
ml/min
Fm. 5. Pressure flow variation.
The viscous drag is the largest resistance in the multicompartment system of which the nonbiologic compartment variables can be controlled as shown in table 2. Few assumptions are made in obtaining the pressure-flow-perfusion data as compared to the biologic compartment where even under the best of circumstances pressure-flow variations require fluoroscopy
for reasonable interpretation. It is emphasized that care be taken to standardize the methodology of the renal pressure-flow-perfusion test to minimize the controllable variations due to needle, perfusion fluid, temperature and flow rate. REFERENCES 1. Whitaker, R. H.: Diagnosis of obstruction in dilated ureters. Ann.
Roy. Coll. Surg. Engl., 53: 153, 1973. 2. Diem, K. and Lentner, C.: Documenta Geigy Scientific Tables. Basel: J. R. Geigy S. A., ed. 7, p. 214, 1970.