Introduction:
Photoplethysmography, or PPG, is an optical technique that measures the volume and volumetric changes in blood circulation by utilizing an infrared light source and detector. This yields an approximate measurement that helps provide crucial information regarding the cardiovascular system and blood circulation in certain body parts.
It is a simple and low-cost approach that can detect changes in blood volume in the vascular tissue bed. This approach works on the principle of light absorption and light reflection by the living tissue's blood vessels. It helps measure the blood volume changes in fingers, wrists, and genital parts. PPG is usually obtained with a pulse oximeter device for the finger. It illuminates the skin tissue of the finger, measuring the changes in light absorption.
What Is Vaginal Photoplethysmography?
Vaginal photoplethysmography (VPG) is a technique that utilizes light sources and light absorbed to detect the amount of blood and blood changes in the walls of the vagina. The device used in this technique is known as a vaginal photometer. Here, a photometer refers to the instrument measuring the potency of electromagnetic radiation right from ultraviolet to infrared light.
History:
Vaginal photoplethysmography, including the vaginal photometer, was first introduced in 1967. The device was then refined in 1975. It was known to be the first reliable and pragmatic device for measuring vaginal blood flow in females. This device constitutes a vaginal probe fabricated to be inserted into the vagina by the subject. Its discovery and introduction increased interest in female sexual arousal in the late 70s and early 80s. The interest in and research on its use in this area have increased lately to a greater extent.
How Does Vaginal Photoplethysmography Work?
The vaginal plethysmography technique uses a device called a vaginal photometer. The device is rod-shaped and has a clear acrylic shell containing a light source and photodetector (light detector). The photodetectors are the sensors of light and certain electromagnetic radiation. So, this light detector senses the light using this technique.
Here, The device and this light detector work on the assumption that the more the light scatters back, the more blood there is in the walls of the vagina. This is achieved by the light source that illuminates and emphasizes the capillary bed of the wall of the vagina and the circulating blood. The amount of light scattered back in this approach is directly associated with the transparency of non-engorged and engorged tissue. Therefore, vaginal photoplethysmography also measures vasoengorgement in addition to blood volume. Vasoengorgement is known to be an indication of sexual arousal.
What Is the Use of Vaginal Photoplethysmography?
The vaginal photoplethysmography technique helps assess the amount of blood in the vaginal walls using light. This device also tries to give an objective measure of sexual arousal in women. This technique involves a vaginal probe designed to be inserted into the vagina by the person.
The signal derived from the vaginal photoplethysmography yields two components. So, the output of vaginal photoplethysmography can be categorized into two distinct types of signals possessing different properties.
The two components obtained from the signals are the following:
1. Vaginal Blood Volume (VBV): The direct current (single directional flow of electric current) measures vaginal blood volume. This value reflects the total volume of blood in the walls of the vaginal tissues. The changes in VBV result from responses to specific stimuli that induce sexuality and anxiety.
2. Vaginal Pulse Amplitude (VPA): The alternating current (current that reverses the direction and changes the magnitude persistently with time, contrary to the direct current) signal gives the measure of vaginal pulse amplitude. This reflects the changes in the blood vessels' pressure in the vaginal wall. This can be associated with each heartbeat. The changes in vaginal pulse amplitude result only from sexual stimuli.
What Are the Advantages of Vaginal Photoplethysmography?
The use of vaginal photoplethysmography as a diagnostic technique for assessing sexual arousal in females possesses many advantages. Some common advantages of vaginal photoplethysmography are listed below:
The ability of the individual to insert the probe of the device in privacy in the absence of assistance is a chief benefit.
It measures the blood volume and blood volume changes
It measures the blood volume of the vagina for a potentially long time without even causing any discomfort or harm to the person.
It may take a short time for VBV and VPA levels to get back to baseline. This makes allowance for numerous and consecutive stimulus recordings.
What Are the Pitfalls of Vaginal Photoplethysmography?
Though the vaginal photometer in vaginal photoplethysmography measures the volume of vaginal blood and vasoengorgement. There are some problems with the vaginal photometer device, which can be a pitfall for this technique.
Lack of validation of whether the results have a direct correlation with vasocongestion.
The tease in each study shows a need for total scale preclusion among the participants.
Research participants say there is inappropriateness in the outcome.
Other Disadvantages:
The technique sometimes fails to measure several aspects of vaginal blood volume and sexual arousal.
The sound theoretical basis has yet to be determined, as it remains unaware of the interpretation of sound and signals.
It fails to measure the sexual response during the time of sexual orgasm beachside if the sensitivity of the probe to the motion contraptions is low.
Moreover, the VPA and VBV levels do not explain whether vasodilation occurs in the venues, veins, arteries, arterioles, and capillaries.
In some tissue regions, an increase in VPA level might represent venous drainage restriction instead of vasodilatation.
Conclusion:
Vaginal photoplethysmography (VPG) is typically used to measure the blood volume and flow in the tissues of the vagina. This approach is most frequently performed these days. This technique includes a long instrumental device that has a probe. This probe can be inserted into the vagina by the subject. The device then measures the blood volume of the vagina using light sources. This technique also helps measure the blood flow changes within the vagina.
