Hypoxia as a potential cause of dyspareunia.

Dyspareunia is defined as genital pain that occurs just before, during or after sexual intercourse. This term is used for both sexes, but for obvious reasons it is more frequently discussed in relation to women [ 1 ]. It was first described in ancient Egypt in the Ramesseum Papyrus, the oldest surviving illustrated Papyrus roll [ 2 ]. Its frequency often depends on the period in a woman’s lifetime. The frequency of dyspareunia ranges from 8–22%, according to different authors [ 3 ]. However, it is thought to be more frequent in women about 40 years of age [ 4 ]. Sexual intercourse concomitant with a pelvic organic lesion or wound is a probable cause of pain in most cases. Another reason could be non-physical aspects of dyspareunia or sexual trauma. Moreover, sexual dysfunctions can cause dyspareunia. Pelvic pain could be present at the site of the pelvic inflammation, vaginal mucous inflammation, discharge, endometriosis, mucous atrophy, pelvic surgery or after other affections [ 5 , 6 ]. However, in these cases the pain depends not only on penile-vaginal intercourse but has an organic origin [ 7 – 9 ]. In most cases it disappears after regular treatment of its origin. It could be better described as vulvodynia. In its essential definition dyspareunia in women is considered an idiopathic condition without a typical organic constitution, i.e. it is only present with penile-vaginal penetration and not followed by any other condition [ 1 , 10 ]. This dysfunction is very often associated with painful spasms of the pelvic muscles [ 11 , 12 ]. For this reason, the term “vaginism” was probably included in this group. This dysfunction is defined as a painful spasm of the pelvic muscles that completely anatomically disables vaginal penetration [ 8 ]. The complex was named GPPPD (genito-pelvic pain or penetration disorder) [ 13 ]. The intensity (level of dyspareunia) was first defined by Marinoff et al. [ 14 ]. The authors proposed a four-point scale ranging from 0–3 (0 = no pain during intercourse, 1 = pain during intercourse that does not prevent intercourse, 2 = pain during intercourse that interrupts intercourse and 3 = pain that prevents intercourse). The scale describes pain limitations during sexual intercourse. Despite proper diagnostics, determining a cause and treatment for dyspareunia remains problematic. Pain associated with muscle, surroundings and interpenetrating fascial tissue seems to be one of the most common diagnoses reported in general practice. Studies have focused on functional principles, including an altered expression of muscle metabolism and enhancing the role of peripheral factors in persistent chronic pain [ 15 – 17 ]. Some studies have reported an increased concentration of end products of anaerobic glycolysis and impairing oxidative metabolism by local hypoxia, presented as an insufficient capacity for muscle recovery because of inflammation and metabolic pattern changes [ 18 ]. Long-term hypoxia in perineal muscles could cause muscle and perimuscular changes, resulting in chronic pain not adequately responding to standard therapy. During the entrance examination to our previous study on dyspareunia, we noted significantly lower pulse oximetry levels in the perineal area of affected women [ 15 , 19 ]. We focused on this event to explain the reason for the muscle and perimuscular changes. Specifically, we aimed to compare pulse oximetry oxygen saturation (SpO2) of dyspareunia-affected women (treatment group) to healthy, pain-free women (controls).

There were 62 participants with 31 in each group ( Table 1 ). The Shapiro-Wilk test confirmed that a Gaussian distribution of the variables was not met. The Mann-Whitney nonparametric U test was run to determine differences in perineum oximetry between the treatment and control groups. The distribution of SpO2 differed statistically between the two groups (p = 0.002). The median SpO2 was 91 in the treatment group and 92 in the control group. We computed the sample size to ensure that a two-sided test with α = 0.05 has 80% power to detect a true effect. With our data, 50 participants (25 per group) were needed, lower than the actual number of study participants (n = 62).

Idiopathic dyspareunia is inherent in cohabitation muscle pain that standard therapy could neither explain nor treat. During the examination, we detected statistically significant decreased levels of SpO2 in our patient cohort. We compared pelvic oximetry between dyspareunia-affected and treated women and healthy controls (no dyspareunia). This comparison showed significant hypoxia in the perineal muscle area (p = 0.002). Our results may help understand the source of this pain and more accurately aim the treatment directly in the defective area. Teaching hospital of Charles University Prague 3.8.2021/10150/EK-Z.

A retrospective study was performed to compare the treatment group with the controls. The study participants were women who took part in our previous study on dyspareunia conducted between 2017 and 2019, following a former feasibility study (previously published) [ 20 ]. All study procedures were conducted in accordance with the ethical standards of the institutional and research committees and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study protocol was approved by the Ethical Committee of the Teaching Hospital at Charles University, Prague, and all patients gave their informed consent and confirmed their participation by signing a consent form. This retrospective study protocol was also approved by the Ethical Committee of the Teaching Hospital at Charles University, Prague. The treatment group included 31 dyspareunia-affected women aged 24–51 (mean age 40) years. This group’s mean body mass index (BMI) was 24.6. The control group comprised 31 women aged 25–52 (mean age 39) years. The mean BMI of the control group was 24.8. The controls, recruited from volunteers taking part in regular prevention examinations, had a medical history free of any known pathology. Both groups were similar in baseline demographic characteristics. All participants in the treatment group were dyspareunia positive with no other disease. They had no pelvic organic reason for their condition, including hormonal changes for dyspareunia, physical changes or a history of sexual trauma. By the time this study was conducted, all the women had fulfilled the study criteria. The inclusion and exclusion criteria for dyspareunia group have been and are published elsewhere and are mentioned consequently for reader’s better comprehension. Inclusion criteria were based on completing all the following criteria of dyspareunia: painful penile-vaginal penetration without pelvic organic reasons primarily connected with pain, a score of >0 on the Marinoff Dyspareunia Scale (Marinoff), a score >0 on a visual analogue scale (VAS), age 20–75 years and a duration of dyspareunia >3 months during the past 6 months. To evaluate discomfort the primary measurement was the Marinoff scale for dyspareunia. In addition, the VAS served as a secondary measure of pain. Patient benefits were unobtainable through other therapeutic approaches. The exclusion criteria were acute pelvic inflammation during the past 6 months, oncological disease within the past 5 years, a clinically significant haematological disease (e.g., haemophilia or other bleeding disorders), myocardial infarction or cardiac arrhythmia within the past 6 months, any serious metabolic disorder (e.g., diabetes with organic changes) and affection in an intended application area.

During their regular examinations, women in the treatment and control groups were measured for SpO2. The oximetry measurements were performed in the posterior commissure of the vagina between the mucous part of the vagina and the dermal part of the perineum, involving the bulbospongiosus muscle ( Fig 1 ). The measurements were done in supine position with the biggest ear-clip sensor pulse oximeter and a plain vital functions measuring gadget. Measurement of SpO2 was recorded as a percentage. SpO2 is determined by measuring the absorption of two emitted light wavelengths, red at 660 nm and near-IR at 940 nm. The light transmitted through the tissue is detected by a photodiode on the opposite side. The pulse oximeter uses the relative amount of red and IR light absorbed to define the proportion of oxyhaemoglobin in deoxyhaemoglobin [ 19 , 21 , 22 ]. The ability of the pulse oximetry to detect SpO2 of only arterial blood is based on the principle that the amount of red and IR light absorbed fluctuates with the cardiac cycle as the arterial blood volume increases during systole and decreases during diastole. The blood volume in the capillaries, veins, fat, skin and bone remains relatively constant [ 19 ]. Because of the nonparametric distribution of SpO2, The data were expressed as medians and ranges. All analyses were conducted using the IBM SPSS software package. We chose the nonparametric Mann-Whitney U test to compare the treatment (dyspareunia) and control (dyspareunia free)groups. Sample size accuracy was determined retroactively using the IBM/Sample power analysis software.