Vaginal plenthysmography in women with dyspareunia

Journal of Sex Research,  May, 1998  by Jan C. Wouda,  Petra M. Hartman,  Riksta M. Bakker,  Jan O. Bakker,  Harry B.M. van de Wiel,  Willibrord C.M. Wiejmar Schultz

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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.