Acta Obstet Gynecol Scand 58: 115-120, 1979
MULTICHANNEL INTRAUTERINE PRESSURE RECORDING BY MEANS OF MICROTRANSDUCERS Ulf Ulmsten and Karl-Erik Andersson From the Department of Obstetrics and Gynecology, University Hospital of Malmii, Sweden, and the Department of Clinical Pharmacology, Institute of Pharmacology. University of Arhus, h h u s , Denmark
Abstract. Intrauterine pressures (IUP) were recorded simultaneously at the fundus, the isthmus, and cervix uteri by means of three micro-transducers (in 20 healthy, nonpregnant women, and in 5 patients with severe, primary dysmenorrhoea). Recordings were performed during the first 3 days of the menstrual cycle. Both incoordinate and coordinated myornetrial activity was recognized. When coordination was present, the contraction wave as a rule started in fundus and was propagated towards the isthmus and cervix. Pinching and/or palpation of the cervix elicited retrograde contractions, i.e. the contraction wave started in the cervix and moved towards the fundus. It was frequently observed that during vigorous contractions of the fundus, the pressure increase in the isthmus was small; in some cases even a decrease in pressure occurred in this region. The pressure recording technique functioned perfectly during all recordings and seems to facilitate detailed studies of myometrial activity in the non-pregnant uterus.
Intrauterine pressure (IUP) recordings as a measure of myometrial activity in the non-pregnant uterus have so far been performed mainly b y the use of fluid-filled open-ended or balloon catheters. These catheter-techniques have several biotechnical disadvantages (for discussions s e e , 9 , 8 , 16). Recently, micro-transducers have been introduced for recording intraluminal pressures in the urinary tract (2, 3); this technique seems also t o be superior t o previously used methods for intrauterine pressure recordings in the non-pregnant uterus (19). The present study w a s undertaken to record simultaneously the I U P in three different parts of the non-pregnant human uterus. Thus, the I U P in the fundus, isthmus, and cervix uteri were recorded with the aid of micro-transducers. The recordings were performed a t the beginning of menstruation, as previous investigators have shown the occurrence of labour-like uterine contractions during this period (13, 15). T h e s e contractions seem t o b e propagated from the fundus t o the cervix uteri ( 5 , 6). It w a s thought that with the present technique it
would b e possible t o elucidate whether myornetrial activity varied in different parts of the uterus, and if coordination of activity w a s recognizable.
METHODS Subjecrs
Twenty healthy women and 5 patients suffering from severe, primary dysmenorrhoea volunteered for the study. Their mean age was 31 years (range 2 4 4 0 years). Before the investigation they were carefully informed of its purpose. The recordings were performed on days 1 to 3 of the menstrual cycle. Two of the women had IUDs (Cu T), and none were on drug therapy when the recordings were performed. Pressure recording technique The recording catheter (Fig. 1) consisted of a teflon catheter which enclosed three micro-transducers (Millar Instruments, Houston, Texas) 3 cm apart. Each pressure sensing section of the catheter had an active pressure sensor area of 0.75 mm2.This allowed recording of the IUP from well-defined positions. Due to its compliance, the frequency response of the microtransducer is more than 2000 Hz, assuring a high sensitivity of the recording system. After amplifying, the pressure signals from the transducers were registered by an Omniscriber WTR 281 (Watanabe, Japan) or by an ink jet recorder (Mingograph 81, Siemens-Elema, Stockholm, Sweden). Before and after every recording, the equipment was calibrated in a special calibrator allowing static, dynamic, and electronic calibration of the instrument (4). Experimental procedure Before the recordings, all patients had a routine gynecological examination and an ultrasound scanning of the pelvic organs. This provided information on the shape and size of the uterine cavity. The size of the uterine cavity was also estimated by sounding. The recording catheter was introduced transcervically into the uterine cavity. It was kept in position by means of sterile compresses surrounding the catheter in the vagina. The recording sections or micro-transducers of the cathe-
I16
U . Ulmsten and K . - E . Atidersson
I
I Fig. I . The pressure recording catheter. Within the frame the distal part of the catheter is shown in larger scale. The three micro-transducers are located 3 cm part. The con-
nection plugs to the amplifier are seen at the proximal end of the catheter.
ter were placed as follows: no. 1 (located at the end of the catheter, see Fig. I ) in the uterine fundus, no. 2 in the isthmic part of the uterine cavity, and no. 3 in the mid part of the cervical canal. All recordings were performed with the subjects in the supine position and with an empty bladder. No anaesthesia was used. The time of recording varied between 80 and 240 min.
subject experienced any discomfort caused by the recording catheter, and no side effects were observed during or after the studies. The absolute values of IUP varied between the women, but also between the different uterine sites in the same woman. In healthy subjects, the resting pressure at the uterine fundus averaged 18 mmHg (range 8-52 mmHg); within the isthmic area, 13 mmHg (range 9 4 6 mmHg) and in the cervical canal the resting pressure as a rule showed small variations; averaging 18 mmHg. The highest contraction pressure amplitude was found at the uterine fundus where it averaged 86 mmHg (range 36-156 mmHg). In the isthmic part of the uterine cavity, the mean pressure amplitude was 71 mmHg (21-1 1 1 mmHg). In the cervical canal, the contraction complexes usually had a small arnplitude, only occasionally exceeding 40 mmHg. In the two females with IUD, the measured parameters did not differ from those found in the other subjects. However, in patients suffering from dysmenorrhoea, both the resting pressure and con-
Interpretation of the records; definitions The resting pressure is defined as the lowest pressure between two consecutive uterine contractions. Contraction pressure amplitude is the difference between resting pressure and the peak pressure of the contractions. Coordinated orpropagated contractions are first recorded by one micro-transducer and after some time lag also by the adjacent transducers (Figs. 3 and 5 ) . lncoordinated or asynchronous contractions are recorded by the different micro-transducers without any time relation. They have often different frequencies at the different regions (Fig. 2).
RESULTS In all investigations, the calibrations before and after the recordings were in complete accordance. N o IUP
rnm Hg
-,--..-----.--w-~-+L~A~~~-----.-
0
0
5
Fig. 2 . Intrauterine pressure recording from a patient with severe, primary dysmenorrhoea. Upper tracing: fundus uteri; middle tracing: isthmus uteri; lower tracing; cervix AcItr O/>\tcJ/ (,\UPLO/ S~t~/fdS8(/979)
10 rnm
uteri. The uterine activity is characterized by asynchronous contractions, high resting pressure, and high contraction pressure amplitudes.
Multichunnel intruicterine prcssirri~recorditlg
I 17
IUP
mm Hg
"1
0 2 min
1
0
Fig. 3. Intrauterine pressure recording from one of the healthy subjects. Upper tracing: fundus uteri; middle tracing: isthmus uteri; lower tracing: cervical canal. The
myometrial contractions start at the fundus and propagate towards the cervix, i.e. in an antegrade direction.
traction pressure amplitudes, although variable, were considerably higher than in the healthy subjects, and uterine activity was often characterized by asynchronous contractions (Fig. 2).
Coordinated myometrial activity was not a consistent finding, but it was observed in all subjects. Three types of coordination could be recognized: (a) Antegrade myometrial activity, i.e. the con-
IUP
h 100
-
mm Hg
0100
-
rnm Hg
/ I
0-
rnm Hg
'1 0
0
5
Fig. 4. Intrauterine pressure recording from one of the healthy subjects. Relatively strong contractions are seen within the fundus (upper tracing). Simultaneously there is
1 0 min
occasionally a decrease in the pressure within the isthmus (middle tracing, arrow).
118
U . Ulmsten and K . - E . Anderson IUP
loo rnrn
-
1
I 0
+.--
1
2 min
Fig. 5 . Intrauterine pressure recording showing a change in direction of contraction waves. Upper tracing: fundus uteri; middle tracing: isthmus uteri; lower tracing: cervix
uteri. In the left part of the figure is seen antegrade propagation which is spontaneously changed to retrograde propagation.
tractions were initiated in the fundus and propagated towards the isthmus and the cervix (Fig. 3). (b) Strong contractions which started in the fundus and were accompanied by a moderate increase or a decrease of the pressure in the isthmus and the cervix (Fig. 4).
(c) Retrograde activity, i.e. the myometrial activity started in the cervix and was propagated towards the fundus (Fig. 5). The last type of activity was seldom seen spontaneously, but could be elicited by palpation or pinching of the cervix. In some women, pressure recordings were also
200-
IUP
mrn Hg
._
0200-
rnrn Hg
0-
h 0
d
.
1
.-A.t
10 min
t
t
t
LVP
Nif
LVP
Fig. 6. Intrauterine pressure recording showing the stimulating effects of lysine vasopressin (LVP) on the intrauterine pressures within the fundus (upper tracing) and isthmus uteri (middle tracing). The effects of vasA c t o Ohsrer G'wiecol S w f i d 5 8 I19791
opressin are counteracted by nifedipine (Nif) 30 mg orally. No effects are seen on the pressures within the cervix (lower tracing).
Multichannel intrauterine pressure recording
performed immediately after ovulation, as judged from basal temperature measurements and vaginal smears. In these, retrograde contractions was easily elicited by touching the cervix. In a few subjects, the spontaneous myometrial activity was increased (Fig. 6) by intravenous injection of lysine vasopressin, 0.2 m u . Both spontaneous and vasopressin induced myometrial activity was reduced by the calcium antagonist nifedipine. (17). The recordings within the fundus and isthmus uteri were very similar in these cases (Fig. 6). DISCUSSION It is generally accepted that the IUP reflects myometrial activity, but so far no ideal method has been devised for its direct translation (9, 1). Because the use of various non-standardized techniques, the results of different IUP recordings have been difficult to compare (8). Even if the IUP technique used in this study is regarded as adequate, artefacts may not be completely excluded. Dependent upon the position of the microtransducer i.e. the sensor area facing the uterine wall or the inside of the uterine cavity-differences in resting pressure and contraction amplitudes might be recorded (19). To avoid these variations, all measurements were made with the micro-transducers facing the upper uterine wall. Because the uterine cavity is not a true cavity but a mere slit, close contact with the uterine wall could be obtained by all the microtransducers. That this actually occurred is supported by the fact that marked arterial pulsations could be recorded by all the recording sections. Because of this contact, the .pressure transducers were most probably directly influenced by contractions of the myometrium. Very few reports of recordings of myometrial activity simultaneously at different parts of the uterus have been presented (see e.g. 5, 10, 14). In accordance with previous results obtained by other recording techniques, the present investigation showed that coordinated myometrial activity occurred during menstrual bleeding. The appearance of retrograde myometrial activity, most pronounced during midcycle, is also in accordance with the resports of Behrman et al. (5). It is interesting to note that retrograde contraction waves could be elicited by palpation or pinching of the cervix. It might be that such retrograde contractions are of importance for the transport of seminal fluid, but further in-
1 19
vestigations are necessary to testify such a speculation. It was often noted that simultaneously with vigorous contractions of the uterine fundus, there was no increase but a decrease of the pressure within the isthmical and cervical parts of the uterus (Fig. 4). From a hydrodynamic point of view, this is a rational response of the uterus to facilitate emptying the cavity of menstrual blood. A high pressure in the cervical and isthmic regions would of course counteract such an emptying procedure. Coordinated myometrial activity was often interrupted by incoordinated contractions. The occurrence of spontaneous changes in uterine activity without correlation to known influences has also been stressed by e.g. Hendricks (12). Most reasonably this non-synchronized myometrial activity is due to local myometrial contractions which, because of the shape of the non-pregnant uterine cavity, are directly recorded by the microtransducers. This suggestion is supported by the findings of Borell et al. (7). They demonstrated by means of hysterography the occurrence of strictly localised myometrial contractions in the non-pregnant uterus. Asynchronous contractions, high resting pressure, and high contraction pressure amplitudes characterized the uterine activity of the women with primary dysmenorrhoea. These findings are in accordance with those reported by other investigators using other techniques of recording (18, 11). Most investigators have stressed the difficulties in characterizing the coordinated activity of the non-pregnant uterus during prolonged recording sessions. It has been suggested that as small recording devices as possible should be used in order not to transform the uterine slit into a real cavity. If this happens, the sum of all local activities will be recorded. The present technique seems to be suitable for recording of myometrial activity in different parts of the uterus. It might be useful for studies of the myometrial activity in patients with dysmenorrhoea, potential retrograde menstruation, and unexplained causes of sterility. REFERENCES method for in vivo determination of pharmacologic effect on the myornetrium. Thesis, Karolinska Institutet, Stockholm, 1977.
1. AnzCn, B.: Hysterometry-a
120
U . Ulrnsten und K.-E. Andersson
2. Asmussen, M. & Ulmsten, U.: Simultaneous urethro-cystometry and urethral pressure profile measurement with a new technique. Acta Obstet Gynecol Scand54: 385, 1975. 3. Asmussen, M. & Ulmsten, U.: A new technique for measurements of the urethral pressure profile. Acta Obstet Gynecol Scand55: 167, 1976. 4. Asmussen, M., Lindstrom, K. & Ulmsten, U.: A catheter-manometer calibrator-a new clinical instrument. Biomed Eng 10: 175, 1975. 5. Behrman, S. J., Archie, J. T. & O’Brien, 0. P.: Myometrial activity and the IUCD. 11. Propagation waves. Am J Obstet Gynecol104: 123, 1969. 6. Bengtsson, L. P.: Hormonal effects on human myometrial activity. In Vitamins and Hormones, vol. 31:257, 1073. Academic Press, New York and London. 7. Borell, U., Fernstrom, I. & Ohlson, L.: Membranelike structures in the uterine cavity. A hysterographic study. Acta Obstet Gynecol Scand49: 185, 1970. 8. Braaksma, J . T., Janssens, J., Eskes, T. K. A. B. & Hein, P. R.: Accurate pressure recording in the nonpregnant uterus. A comparison of open and closed tip catheter. Eur J Obstet Gynecol6: 195, 1971. 9. Csapo, A.: The diagnostic significance of the intrauterine pressure. Obstet Gynecol Surv5: 403, 1970. 10. Csapo, A. I. & Pinto-Dantas, C. R.: The cyclic activity of the nonpregnant human uterus. A new method for recording intrauterine pressure. Fertil Steril 17:34, 1966. 1 1 . Filler, W. W. & Hall, W. C.: Dysmenorrhea and its therapy: A uterine contractility study. Am J Obstet Gynecol106: 104, 1970.
Acto Oh.stet Gynecol Sciind 58 (1979)
12. Hendricks, C. H.: In vivo studies of motility patterns in the nonpregnant human uterus. Obstet Gynecol 25:421, 1965. 13. Hendricks, C. H.: Inherent motility patterns and response charactristics of the non-pregnant human uterus. Am J Obstet Gynecol %: 824, 1%6. 14. Martinez-Gaudio, M., Yoshida, T . & Bengtsson, L. P.: Propagated and nonpropagated myometrial contractions in normal menstrual cycles. Obstet Gynecol 115: 107, 1973. 15. Moawad, A. H. & Bengtsson, L. P.: In vivo studies of the motility patterns of the non-pregnant human uterus. I. The normal menstrual cycle. Am J Obstet Gynecol98: 1057, 1967. 16. Ulmsten, U.: Studies on ureteral function in women. Thesis, University of Lund, 1974. 17. Ulmsten, U., Andersson, K.-E. & Forman, A.: Relaxing effects of nifedipine on non-pregnant human uterus in vitro and in vivo. In manuscript, 1977. 18. Woodbury, R. A., Torpin, R., Child, G. P., Watson, H. & Jarboe, M.: Myometrial physiology and its relation to pelvic pain. J Am Med Ass 134: 104, 1970. 19. Akerlund, M., Bengtsson, L. P. & Ulmsten, U.: Recording of myometrial activity in the nonpregnant uterus by a micro-transducer catheter. In press. Submitted for publication Oct. 26, 1977
Ulf Ulmsten Department of Obstetrics and Gynecology University Hospital S-21401 Malmo Sweden
MULTICHANNEL INTRAUTERINE PRESSURE RECORDING BY MEANS OF MICROTRANSDUCERS Ulf Ulmsten and Karl-Erik Andersson From the Department of Obstetrics and Gynecology, University Hospital of Malmii, Sweden, and the Department of Clinical Pharmacology, Institute of Pharmacology. University of Arhus, h h u s , Denmark
Abstract. Intrauterine pressures (IUP) were recorded simultaneously at the fundus, the isthmus, and cervix uteri by means of three micro-transducers (in 20 healthy, nonpregnant women, and in 5 patients with severe, primary dysmenorrhoea). Recordings were performed during the first 3 days of the menstrual cycle. Both incoordinate and coordinated myornetrial activity was recognized. When coordination was present, the contraction wave as a rule started in fundus and was propagated towards the isthmus and cervix. Pinching and/or palpation of the cervix elicited retrograde contractions, i.e. the contraction wave started in the cervix and moved towards the fundus. It was frequently observed that during vigorous contractions of the fundus, the pressure increase in the isthmus was small; in some cases even a decrease in pressure occurred in this region. The pressure recording technique functioned perfectly during all recordings and seems to facilitate detailed studies of myometrial activity in the non-pregnant uterus.
Intrauterine pressure (IUP) recordings as a measure of myometrial activity in the non-pregnant uterus have so far been performed mainly b y the use of fluid-filled open-ended or balloon catheters. These catheter-techniques have several biotechnical disadvantages (for discussions s e e , 9 , 8 , 16). Recently, micro-transducers have been introduced for recording intraluminal pressures in the urinary tract (2, 3); this technique seems also t o be superior t o previously used methods for intrauterine pressure recordings in the non-pregnant uterus (19). The present study w a s undertaken to record simultaneously the I U P in three different parts of the non-pregnant human uterus. Thus, the I U P in the fundus, isthmus, and cervix uteri were recorded with the aid of micro-transducers. The recordings were performed a t the beginning of menstruation, as previous investigators have shown the occurrence of labour-like uterine contractions during this period (13, 15). T h e s e contractions seem t o b e propagated from the fundus t o the cervix uteri ( 5 , 6). It w a s thought that with the present technique it
would b e possible t o elucidate whether myornetrial activity varied in different parts of the uterus, and if coordination of activity w a s recognizable.
METHODS Subjecrs
Twenty healthy women and 5 patients suffering from severe, primary dysmenorrhoea volunteered for the study. Their mean age was 31 years (range 2 4 4 0 years). Before the investigation they were carefully informed of its purpose. The recordings were performed on days 1 to 3 of the menstrual cycle. Two of the women had IUDs (Cu T), and none were on drug therapy when the recordings were performed. Pressure recording technique The recording catheter (Fig. 1) consisted of a teflon catheter which enclosed three micro-transducers (Millar Instruments, Houston, Texas) 3 cm apart. Each pressure sensing section of the catheter had an active pressure sensor area of 0.75 mm2.This allowed recording of the IUP from well-defined positions. Due to its compliance, the frequency response of the microtransducer is more than 2000 Hz, assuring a high sensitivity of the recording system. After amplifying, the pressure signals from the transducers were registered by an Omniscriber WTR 281 (Watanabe, Japan) or by an ink jet recorder (Mingograph 81, Siemens-Elema, Stockholm, Sweden). Before and after every recording, the equipment was calibrated in a special calibrator allowing static, dynamic, and electronic calibration of the instrument (4). Experimental procedure Before the recordings, all patients had a routine gynecological examination and an ultrasound scanning of the pelvic organs. This provided information on the shape and size of the uterine cavity. The size of the uterine cavity was also estimated by sounding. The recording catheter was introduced transcervically into the uterine cavity. It was kept in position by means of sterile compresses surrounding the catheter in the vagina. The recording sections or micro-transducers of the cathe-
I16
U . Ulmsten and K . - E . Atidersson
I
I Fig. I . The pressure recording catheter. Within the frame the distal part of the catheter is shown in larger scale. The three micro-transducers are located 3 cm part. The con-
nection plugs to the amplifier are seen at the proximal end of the catheter.
ter were placed as follows: no. 1 (located at the end of the catheter, see Fig. I ) in the uterine fundus, no. 2 in the isthmic part of the uterine cavity, and no. 3 in the mid part of the cervical canal. All recordings were performed with the subjects in the supine position and with an empty bladder. No anaesthesia was used. The time of recording varied between 80 and 240 min.
subject experienced any discomfort caused by the recording catheter, and no side effects were observed during or after the studies. The absolute values of IUP varied between the women, but also between the different uterine sites in the same woman. In healthy subjects, the resting pressure at the uterine fundus averaged 18 mmHg (range 8-52 mmHg); within the isthmic area, 13 mmHg (range 9 4 6 mmHg) and in the cervical canal the resting pressure as a rule showed small variations; averaging 18 mmHg. The highest contraction pressure amplitude was found at the uterine fundus where it averaged 86 mmHg (range 36-156 mmHg). In the isthmic part of the uterine cavity, the mean pressure amplitude was 71 mmHg (21-1 1 1 mmHg). In the cervical canal, the contraction complexes usually had a small arnplitude, only occasionally exceeding 40 mmHg. In the two females with IUD, the measured parameters did not differ from those found in the other subjects. However, in patients suffering from dysmenorrhoea, both the resting pressure and con-
Interpretation of the records; definitions The resting pressure is defined as the lowest pressure between two consecutive uterine contractions. Contraction pressure amplitude is the difference between resting pressure and the peak pressure of the contractions. Coordinated orpropagated contractions are first recorded by one micro-transducer and after some time lag also by the adjacent transducers (Figs. 3 and 5 ) . lncoordinated or asynchronous contractions are recorded by the different micro-transducers without any time relation. They have often different frequencies at the different regions (Fig. 2).
RESULTS In all investigations, the calibrations before and after the recordings were in complete accordance. N o IUP
rnm Hg
-,--..-----.--w-~-+L~A~~~-----.-
0
0
5
Fig. 2 . Intrauterine pressure recording from a patient with severe, primary dysmenorrhoea. Upper tracing: fundus uteri; middle tracing: isthmus uteri; lower tracing; cervix AcItr O/>\tcJ/ (,\UPLO/ S~t~/fdS8(/979)
10 rnm
uteri. The uterine activity is characterized by asynchronous contractions, high resting pressure, and high contraction pressure amplitudes.
Multichunnel intruicterine prcssirri~recorditlg
I 17
IUP
mm Hg
"1
0 2 min
1
0
Fig. 3. Intrauterine pressure recording from one of the healthy subjects. Upper tracing: fundus uteri; middle tracing: isthmus uteri; lower tracing: cervical canal. The
myometrial contractions start at the fundus and propagate towards the cervix, i.e. in an antegrade direction.
traction pressure amplitudes, although variable, were considerably higher than in the healthy subjects, and uterine activity was often characterized by asynchronous contractions (Fig. 2).
Coordinated myometrial activity was not a consistent finding, but it was observed in all subjects. Three types of coordination could be recognized: (a) Antegrade myometrial activity, i.e. the con-
IUP
h 100
-
mm Hg
0100
-
rnm Hg
/ I
0-
rnm Hg
'1 0
0
5
Fig. 4. Intrauterine pressure recording from one of the healthy subjects. Relatively strong contractions are seen within the fundus (upper tracing). Simultaneously there is
1 0 min
occasionally a decrease in the pressure within the isthmus (middle tracing, arrow).
118
U . Ulmsten and K . - E . Anderson IUP
loo rnrn
-
1
I 0
+.--
1
2 min
Fig. 5 . Intrauterine pressure recording showing a change in direction of contraction waves. Upper tracing: fundus uteri; middle tracing: isthmus uteri; lower tracing: cervix
uteri. In the left part of the figure is seen antegrade propagation which is spontaneously changed to retrograde propagation.
tractions were initiated in the fundus and propagated towards the isthmus and the cervix (Fig. 3). (b) Strong contractions which started in the fundus and were accompanied by a moderate increase or a decrease of the pressure in the isthmus and the cervix (Fig. 4).
(c) Retrograde activity, i.e. the myometrial activity started in the cervix and was propagated towards the fundus (Fig. 5). The last type of activity was seldom seen spontaneously, but could be elicited by palpation or pinching of the cervix. In some women, pressure recordings were also
200-
IUP
mrn Hg
._
0200-
rnrn Hg
0-
h 0
d
.
1
.-A.t
10 min
t
t
t
LVP
Nif
LVP
Fig. 6. Intrauterine pressure recording showing the stimulating effects of lysine vasopressin (LVP) on the intrauterine pressures within the fundus (upper tracing) and isthmus uteri (middle tracing). The effects of vasA c t o Ohsrer G'wiecol S w f i d 5 8 I19791
opressin are counteracted by nifedipine (Nif) 30 mg orally. No effects are seen on the pressures within the cervix (lower tracing).
Multichannel intrauterine pressure recording
performed immediately after ovulation, as judged from basal temperature measurements and vaginal smears. In these, retrograde contractions was easily elicited by touching the cervix. In a few subjects, the spontaneous myometrial activity was increased (Fig. 6) by intravenous injection of lysine vasopressin, 0.2 m u . Both spontaneous and vasopressin induced myometrial activity was reduced by the calcium antagonist nifedipine. (17). The recordings within the fundus and isthmus uteri were very similar in these cases (Fig. 6). DISCUSSION It is generally accepted that the IUP reflects myometrial activity, but so far no ideal method has been devised for its direct translation (9, 1). Because the use of various non-standardized techniques, the results of different IUP recordings have been difficult to compare (8). Even if the IUP technique used in this study is regarded as adequate, artefacts may not be completely excluded. Dependent upon the position of the microtransducer i.e. the sensor area facing the uterine wall or the inside of the uterine cavity-differences in resting pressure and contraction amplitudes might be recorded (19). To avoid these variations, all measurements were made with the micro-transducers facing the upper uterine wall. Because the uterine cavity is not a true cavity but a mere slit, close contact with the uterine wall could be obtained by all the microtransducers. That this actually occurred is supported by the fact that marked arterial pulsations could be recorded by all the recording sections. Because of this contact, the .pressure transducers were most probably directly influenced by contractions of the myometrium. Very few reports of recordings of myometrial activity simultaneously at different parts of the uterus have been presented (see e.g. 5, 10, 14). In accordance with previous results obtained by other recording techniques, the present investigation showed that coordinated myometrial activity occurred during menstrual bleeding. The appearance of retrograde myometrial activity, most pronounced during midcycle, is also in accordance with the resports of Behrman et al. (5). It is interesting to note that retrograde contraction waves could be elicited by palpation or pinching of the cervix. It might be that such retrograde contractions are of importance for the transport of seminal fluid, but further in-
1 19
vestigations are necessary to testify such a speculation. It was often noted that simultaneously with vigorous contractions of the uterine fundus, there was no increase but a decrease of the pressure within the isthmical and cervical parts of the uterus (Fig. 4). From a hydrodynamic point of view, this is a rational response of the uterus to facilitate emptying the cavity of menstrual blood. A high pressure in the cervical and isthmic regions would of course counteract such an emptying procedure. Coordinated myometrial activity was often interrupted by incoordinated contractions. The occurrence of spontaneous changes in uterine activity without correlation to known influences has also been stressed by e.g. Hendricks (12). Most reasonably this non-synchronized myometrial activity is due to local myometrial contractions which, because of the shape of the non-pregnant uterine cavity, are directly recorded by the microtransducers. This suggestion is supported by the findings of Borell et al. (7). They demonstrated by means of hysterography the occurrence of strictly localised myometrial contractions in the non-pregnant uterus. Asynchronous contractions, high resting pressure, and high contraction pressure amplitudes characterized the uterine activity of the women with primary dysmenorrhoea. These findings are in accordance with those reported by other investigators using other techniques of recording (18, 11). Most investigators have stressed the difficulties in characterizing the coordinated activity of the non-pregnant uterus during prolonged recording sessions. It has been suggested that as small recording devices as possible should be used in order not to transform the uterine slit into a real cavity. If this happens, the sum of all local activities will be recorded. The present technique seems to be suitable for recording of myometrial activity in different parts of the uterus. It might be useful for studies of the myometrial activity in patients with dysmenorrhoea, potential retrograde menstruation, and unexplained causes of sterility. REFERENCES method for in vivo determination of pharmacologic effect on the myornetrium. Thesis, Karolinska Institutet, Stockholm, 1977.
1. AnzCn, B.: Hysterometry-a
120
U . Ulrnsten und K.-E. Andersson
2. Asmussen, M. & Ulmsten, U.: Simultaneous urethro-cystometry and urethral pressure profile measurement with a new technique. Acta Obstet Gynecol Scand54: 385, 1975. 3. Asmussen, M. & Ulmsten, U.: A new technique for measurements of the urethral pressure profile. Acta Obstet Gynecol Scand55: 167, 1976. 4. Asmussen, M., Lindstrom, K. & Ulmsten, U.: A catheter-manometer calibrator-a new clinical instrument. Biomed Eng 10: 175, 1975. 5. Behrman, S. J., Archie, J. T. & O’Brien, 0. P.: Myometrial activity and the IUCD. 11. Propagation waves. Am J Obstet Gynecol104: 123, 1969. 6. Bengtsson, L. P.: Hormonal effects on human myometrial activity. In Vitamins and Hormones, vol. 31:257, 1073. Academic Press, New York and London. 7. Borell, U., Fernstrom, I. & Ohlson, L.: Membranelike structures in the uterine cavity. A hysterographic study. Acta Obstet Gynecol Scand49: 185, 1970. 8. Braaksma, J . T., Janssens, J., Eskes, T. K. A. B. & Hein, P. R.: Accurate pressure recording in the nonpregnant uterus. A comparison of open and closed tip catheter. Eur J Obstet Gynecol6: 195, 1971. 9. Csapo, A.: The diagnostic significance of the intrauterine pressure. Obstet Gynecol Surv5: 403, 1970. 10. Csapo, A. I. & Pinto-Dantas, C. R.: The cyclic activity of the nonpregnant human uterus. A new method for recording intrauterine pressure. Fertil Steril 17:34, 1966. 1 1 . Filler, W. W. & Hall, W. C.: Dysmenorrhea and its therapy: A uterine contractility study. Am J Obstet Gynecol106: 104, 1970.
Acto Oh.stet Gynecol Sciind 58 (1979)
12. Hendricks, C. H.: In vivo studies of motility patterns in the nonpregnant human uterus. Obstet Gynecol 25:421, 1965. 13. Hendricks, C. H.: Inherent motility patterns and response charactristics of the non-pregnant human uterus. Am J Obstet Gynecol %: 824, 1%6. 14. Martinez-Gaudio, M., Yoshida, T . & Bengtsson, L. P.: Propagated and nonpropagated myometrial contractions in normal menstrual cycles. Obstet Gynecol 115: 107, 1973. 15. Moawad, A. H. & Bengtsson, L. P.: In vivo studies of the motility patterns of the non-pregnant human uterus. I. The normal menstrual cycle. Am J Obstet Gynecol98: 1057, 1967. 16. Ulmsten, U.: Studies on ureteral function in women. Thesis, University of Lund, 1974. 17. Ulmsten, U., Andersson, K.-E. & Forman, A.: Relaxing effects of nifedipine on non-pregnant human uterus in vitro and in vivo. In manuscript, 1977. 18. Woodbury, R. A., Torpin, R., Child, G. P., Watson, H. & Jarboe, M.: Myometrial physiology and its relation to pelvic pain. J Am Med Ass 134: 104, 1970. 19. Akerlund, M., Bengtsson, L. P. & Ulmsten, U.: Recording of myometrial activity in the nonpregnant uterus by a micro-transducer catheter. In press. Submitted for publication Oct. 26, 1977
Ulf Ulmsten Department of Obstetrics and Gynecology University Hospital S-21401 Malmo Sweden
