Vaginal plenthysmography in women with dyspareunia.

Dyspareunia, pain in the genital region during sexual intercourse that severely disrupts sexual functioning, is one of the most common types of sexual dysfunction encountered in both general practice and gynecological practice. About 61% of all women who are sexually active (or have been sexually active) have suffered from dyspareunia (Glatt, Zinner, & McCormack, 1990).

Etiologists believe that there is a continuum of factors contributing to dyspareunia. Dyspareunia often has a physical cause but can also be caused by psychological factors (Sandberg & Quevillon, 1987).

Masters and Johnson (1966) described the mechanism of female sexual arousal in terms of an increase in vaginal vasocongestion and lubrication. A larger cardiac pulse volume and relaxation of the smooth muscle tissue in the arterioles that supply the genital organs increase the pressure in the vaginal capillary bed and cause plasma transudate to leak from the capillaries and to moisten the vaginal wall. This reaction generally takes place fairly swiftly, mainly under the influence of parasympathetic stimulation (Bancroft, 1989; Levin, 1992; Wagner & Ottesen, 1980).

Bancroft (1989) proposed that too little lubrication as a result of insufficient vasocongestion plays an important role in the pathophysiology of dyspareunia. Palace & Gorzalka (1990; 1992) found that while watching an erotic film, women with sexual dysfunctions--including a number of women with dyspareunia--had a lower genital response than did women in the control group.

Laan (1994) investigated the relation between these genital reactions and subjective indications of sexual arousal in healthy female respondents. She used vaginal plethysmography to measure vasocongestion (Geer, Morokoff, & Greenwood, 1974) and concluded that the genital response to sexual arousal is a highly automatized mechanism. When the women were exposed to erotic stimuli, such as an erotic film, there was an almost immediate increase in vasocongestion in the vaginal wall. This response was also observed in the women who reported that they felt only slightly sexually aroused or not aroused at all, those who expressed a negative opinion about the erotic stimulus, and those in whom the stimulus gave rise to negative emotions.

Thus, we can assume that there is little or no disruption of vasocongestion and lubrication during sexual arousal in women with dyspareunia, provided that there are no somatic abnormalities (anatomical or hormonal) to which the decreased genital reaction can be attributed. We, therefore, expected that the negative feelings, owing to associations with pain, these women experience while watching a sexual intercourse video scene, would not influence their genital response. In this study, we tested this assumption about the autonomy of the genital reaction during sexual stimulation in women with dyspareunia.

METHODS

Participants

The study group comprised 18 women with dyspareunia who were referred to the Sexology Outpatient Department of the University Hospital Groningen for treatment for this complaint. The control group comprised 16 women recruited through an advertisement in a local newspaper. All of the women were informed about the aim of the study and the test procedure and signed an informed consent form before participation.

Measures

Vaginal plethysmography. To measure the level of vaginal vasocongestion, we used a vaginal plethysmograph (manufactured by Farrall Instruments, Inc., Nebraska). The plethysmograph consists of a tampon of transparent plastic containing a light source and a photocell (see Figure 1).

[Figure 1 ILLUSTRATION OMITTED]

The amount of light from the light source that is reflected by the vaginal wall depends on the level of vasocongestion in the vaginal wall. Changes in light intensity are converted into an electrical resistance by the photocell. The signal is subsequently converted into an electrical current (measured in volts) and then amplified, filtered, and made suitable for further statistical analysis by analogue-digital conversion (sample frequency of 10 Hz). During the test, a fixed amplification factor (range 0-8 volts) and a fixed time constant (5 sec.) were used for the filter. Therefore, a valid comparison could be made of the signal characteristics of all of the recordings obtained.

During the test, each woman sat in a comfortable chair in a room isolated from the measurement equipment. Before use, the vaginal plethysmograph was desinfected according to the manufacturer's specifications with Cidex-7. The tampon was lubricated with Sensilube to facilitate insertion. After the test procedure had been explained thoroughly, each woman was instructed on how to insert the tampon. The tampon was always placed at a fixed position inside the vagina with the aid of a plastic ring mounted on the cord of the tampon (Laan, 1994). After the woman inserted the tampon, she was given at least five minutes to acclimate to the study situation and to relax.

Sexual arousal. For the subsequent five minutes, the vaginal blood flow was measured at rest to obtain a baseline value (Phase 1). Then the woman was shown a video fragment about eight minutes long showing mainly oral (cunnilingus and fellatio) sexual activities (Phase 2). After this phase, the respondent rested for ten minutes while attempting to solve a brainteaser task (Tangram figure formation), which served as a distraction from the erotic stimuli (Phase 3). The test then proceeded with a five-minute video fragment showing a cunnilingus scene (Phase 4), followed by a five-minute fragment from the same film showing coitus (Phase 5). There was no rest period between the scenes.

Questionnaires. After all of the measurements were taken, the subject completed two questionnaires. The Genital Experience Question List (Dekker, 1988) was used to establish the extent to which the respondent felt sexually aroused while watching the video fragments and to obtain her opinion about the quality of the video fragments. The second questionnaire was an extended version of the Groninger Arousability Scale (Weijmar Schultz & van de Wiel, 1991). This scale comprises a number of subscales that measure various aspects of sexuality and arousal: sexual satisfaction (four questions), variation in behavior during intercourse (six questions), genital stimulation during arousal (five questions), experiencing orgasm (four questions), capacity to become aroused (six questions), and unpleasant feelings (pain) during sexual intercourse (six questions). In addition, several demographic and medical data were obtained: age, education level, sexual experience, type of relationship, medical treatment, and pregnancies.

Analysis of the plethysmographic signals. One-minute signal fragments were selected from the plethysmographic measurements of each respondent in the five test phases. The last minute of the recordings of each phase was chosen unless it was disturbed by movement artifacts. When artifacts were present in this last minute of the recording, which was the case in about 10% of the measurements, the minute of the recording just preceding the artifacts was chosen. Figure 2 shows the one-minute signal of one of the respondents during the second rest interval and the one-minute signal during the coital (fifth) phase.

[Figure 2 ILLUSTRATION OMITTED]

Both signals show a rapid wave pattern superimposed on a slow wave pattern. The rapid wave is the vaginal pulse rate, that is, the pulsation of the vaginal wall resulting from the heartbeat. The amplitude of this vaginal pulse wave is a reliable measure of the genital response during sexual arousal (Laan, 1994). Figure 2 shows that this amplitude was much higher in the coital phase than in the rest phase. The slow wave pattern in the rest phase mainly reflects the breathing rhythm.

Further analysis of the plethysmographic signals comprised a frequency analysis (Fourier analysis) of the selected signal fragments (Stephenson, 1971). In frequency analysis, the complex waveforms in the signal are unraveled into waves with the same frequency (waves/min.). The frequency spectrum reflects the (energy) contribution of these simple waves to the total signal. This contribution, measured in volts, is referred to as the spectral tension. Figure 3 shows the frequency spectra of the two signals diplayed in Figure 2. The peaks between 5 and 25 waves/minute are mainly caused by breathing. The peak between 50 and 100 waves/minute is the spectral representation of the amplitude of the vaginal pulse. The height of this peak is, therefore, a measure of the genital response during sexual arousal.

[Figure 3 ILLUSTRATION OMITTED]

For each respondent,we calculated two parameters from the frequency spectra obtained from each of the five test phases: (1) the peak frequency of the vaginal pulse (in waves/min.); (2) the spectral tension (height of the peak) of the vaginal pulse frequency (in volts).

In the statistical analysis, the pulse frequency and the spectral tension in the first rest interval were taken as baseline values to compensate for any interindividual variation in these parameters. The changes in pulse frequency from the second to the fifth measurement phases are expressed as difference scores in relation to these baseline values. The changes in spectral tension ([V.sub.n]) are expressed in normally distributed decibel scores in relation to the baseline value ([V.sub.0]) according to the fonnula dB = 20Log [V.sub.n]/[V.sub.0].

The statistical analysis comprised a repeated-measure analysis of variance, with the test phase as a within-group factor, the study group (patient versus control) as a between-group factor, and the baseline value (first rest interval) as a covariant. Separate variance analyses were performed for the two dependent variables, the difference scores in pulse frequency and the decibel scores.

RESULTS

Demographic and Medical Data

The average age of the women with dyspareunia was 25 (range 21-34) years. In 12 cases, there was no demonstrable somatic cause for the dyspareunia; six women were suffering from a somatic problem (mainly inflammation). Fourteen patients had a steady (male) partner, one patient had multiple partners, and three patients did not have a partner.

The average age in the control group was also 25 (range 20-35) years. Fourteen of them had a steady partner and two had multiple partners. The average education level in the two groups was between higher vocational education and pre-university education. The education level of the control group was slightly higher than that of the patients. All of the women had heterosexual experience, and the two groups were comparable on this aspect. None of the women had ever given birth or undergone an operation in the genital area.

Changes in Pulse Frequency and Spectral Tension

Figure 4 shows the average vaginal pulse frequencies of the two groups during the five test phases. During the test, for both groups, there was a decrease in the vaginal pulse frequency relative to the frequency in the first baseline phase.

[Figure 4 ILLUSTRATION OMITTED]

Table 1 shows the difference scores of the pulse frequencies during the test phases in relation to the baseline value (rest phase). There was a significant main effect for the differences between the test phases, F(3,30) = 8.75; p [is less than] .001. There was no difference between the dyspareunia group and the control group regarding these changes in vaginal pulse frequence.

Table 1. Average Difference Scores of the Pulse Frequencies
(Waves/Min.) in Phases 2-5 Versus the Rest Phase

                                     Difference Scores

                           Dyspareunia Group         Control Group
        Phase                   (N = 18)                (N = 16)

2. Oral Scene                    -5.83                    -2.94
                                 (5.89)                   (6.48)
3. Second Rest                   -6.50                    -4.12
                                 (5.34)                   (8.51)
4. Cunnilingus Scene             -8.83                    -7.25
                                 (4.77)                   (8.36)
5. Coitus Scene                  -9.00                    -6.44
                                 (6.40)                   (7.27)

Note. Standard deviations are in parentheses.

Figure 5 shows the average spectral tension of the two groups during the five test phases. From the first to the fourth test phase, the average spectral tension was almost the same in the two groups. However, while the women watched the coitus scene, the spectral tension differed between the two groups.

[Figure 5 ILLUSTRATION OMITTED]

In Table 2, these changes in spectral tension are expressed in decibels in relation to the baseline values. There was a significant main effect for the differences between the test phases, F(3,30) = 38.31; p [is less than] 0.001. There was no main effect for the differences between the two groups, F(1,31) = 1.10; p = .30. Calculated over all five test phases, the Phase x Group interaction barely reached significance, F(3,30) = 3.30; p = 0.03. However, when only the changes in the last two test phases were considered, there was a significant main effect for the group differences, F(1,31) = 31.78; p [is less than] .001, and a significant Phase X Group interaction, F(1,30) = 34.22; p [is less than] .001. These results demonstrate that there was a difference between the two groups while they were watching the coitus scene: In the control group the genital response increased further, whereas in the dyspareunia group the response decreased.

Table 2. Average Change in the Spectral Tension (dB) in Phases 2-5 Versus Baseline (Rest) Values

                              Change in Spectral Tension
    Test Phase          Dyspareunia Group       Control Group
                             (N = 18)              (N = 16)

2. Oral Scene                 10.34                  7.85
                              (4.48)                (4.02)
3. Second Rest                 5.65                  2.28
                              (3.61)                (4.41)
4. Cunnilingus Scene          10.97                  7.67
                              (4.19)                (4.43)
5. Coitus Scene                9.97                  9.18
                              (4.80)                (3.81)
Change in Coitus              -1.00                  1.51
Phase vs. Cunni-              (1.91)                (2.78)
lingus Phase
t-Value                        2.23(*)               2.17(*)

Note. Standard deviations are in parentheses.

(*) p < .01.

Questionnaires

Table 3 shows the average scores on the subscales of the Groninger Arousability Scale. The table shows that the dyspareunia group differed in a number of respects from the control group regarding their experience of sexuality. The dyspareunia patients were less satisfied with their sex life, showed less variation in their behavior during sexual intercourse, had more difficulty becoming sexually aroused, and (as expected) had more unpleasant feelings (pain) during sexual intercourse.

Table 3. Average scores on the Subscales of the Groninger
Arousability Scale (GAS)

                                          Average Scores
                                  Dyspareunia         Control
   Subscales of GAS                (N = 18)           (N = 16)

Sexual Satisfaction                   9.73              14.07
                                     (2.52)            (1.39)
Variation in Behaviour               22.72              26.06
                                     (3.72)             (2.52)
Genital Feelings                     15.33              16.44
During Arousal                       (3.41)             (2.68)
Experiencing Orgasm                  11.06              13.75
                                     (3.60)             (1.77)
Capacity To Become                   14.44              19.81
  Aroused                            (3.93)             (2.14)
Unpleasant Feelings                  19.47               8.75
                                     (2.88)             (1.73)

                                                 Correlation With
                                                 Spectral Changes
                                  t-test          in Coitus vs.
   Subscales of GAS             (df = 32)       Cunnilingus Phase

Sexual Satisfaction              5.83(**)             .42(**)

Variation in Behaviour           3.02(*)              .42(**)
Genital Feelings                 1.04                -.05
During Arousal
Experiencing Orgasm              2.70                 .33

Capacity To Become               4.86(**)             .36
  Aroused
Unpleasant Feelings             12.67(**)            -.49(**)

By calculating Pearson's correlation coefficients between the scores on these subscales and the changes in spectral tension between the coitus phase versus the cunnilingus phase, we investigated the extent to which these differences in sexuality were correlated with the difference in reactions to the coitus scene. The resulting correlations, presented in column 4 in Table 3, were significant for sexual satisfaction, variation in behavior during sexual intercourse, and unpleasant feelings during sexual intercourse.

The two groups did not differ in the levels of arousal they reported experiencing during the test or in their opinions about the erotic fragments. Moreover, there was no relation between the questionnaire responses and the (changes in) spectral tension values.

DISCUSSION

Diverse findings have been reported about the changes in heart rate during the first phase of sexual arousal (Bancroft, 1989; Laan, 1994; Levin, 1992; Masters & Johnson, 1966). In the women who participated in our study, there was a decrease in the vaginal pulse frequency (and therefore in heart rate) during the five test phases. This decrease in pulse rate may have occurred because the women gradually became more relaxed as the test progressed. However, this decrease may have been due partly to increased activity of the parasympathetic system in the first phase of sexual arousal.

The results showed clearly that for women with dyspareunia, the level of vaginal vasocongestion was generally the same as that for women without dyspareunia. These results are consistent with Laan's (1994) findings that vasocongestion is an automatic response to sexual stimulation. Our results contradict the assumption made by Bancroft (1989) and Palace & Gorzalka (1990; 1992) that decreased vasocongestion is an important factor in the development of dyspareunia and the persistence of related symptoms. On the other hand, we found that the level of vasocongestion for women with dyspareunia decreased while they watched the coitus scene; but for women in the control group, there was a further increase in the genital response. It is, therefore, possible that the women with dyspareunia felt a slight aversion toward the coitus scene, which influenced their genital response. Apparently, the autonomy of the genital response has limits. The correlations between the decrease in vaginal vasocongestion and several subscales of the Groninger Arousability Scale--particularly the subscale regarding pain during sexual intercourse--support this assumption.

That the dyspareunia patients and the control group found the coitus scene equally arousing indicates that the dyspareunia patients were obviously unaware of having a negative reaction. We conclude that during sexual arousal, there was no disruption of vasocongestion in the vaginal wall of the women with dyspareunia. However, for these women there was an unconscious reaction of aversion to (watching) coitus, which inhibited any further increase in the genital response.

REFERENCES

Bancroft, J. (1989). Human Sexuality and Its Problems. Edinburgh, Scotland: Churchill Livingstone.

Dekker, J. (1988). Voluntary control of sexual arousal. Unpublished master's thesis, State University Utrecht, The Netherlands.

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Glatt, A. E., Zinner, S. H., & McCormack, W. M. (1990). The prevalence of dyspareunia. Obstetrics & Gynecology, 75, 433-436.

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Palace, E. M., & Gorzalka, B. B. (1992). Differential patterns of arousal in sexually functional and dysfunctional women: Physiological and subjective components of sexual response. Archives of Sexual Behaviour, 21,135-159.

Sandberg, G., & Quevillon, R. P. (1987). Dyspareunia: an integrated approach to assessment and diagnosis. Journal of Family Practice, 24, 66--69.

Stephenson, G. (1971). Mathematical methods for science students. London: Longman.

Wagner, G., & Ottesen, B. (1980). Vaginal blood flow during sexual stimulation. Obstetrics & Gynecology, 56, 621-624.

Weijmar Schultz, W. C. M., & Wiel, H. B. M. van de (1991). Sexual functioning after gynecological cancer treatment. Unpublished master's thesis, State University Groningen, The Netherlands.

Manuscript accepted on 3/13/97.

Address correspondence to Willibrord Weijmar Schultz, M.D., Ph.D., Department of Obstetrics and Gynecology, Hanzeplein 1, P.O. Box 30.001, 9700 RB Groningen, The Netherlands; e-mail: [e-mail].