A plethysmograph measures the volume of different body parts and can be used to help with issues such as air passage restrictions, poor blood circulation, and sexual arousal issues in men. There are different types, including lung, respiratory, and penile plethysmographs, which measure the volume of different body parts. Lung plethysmographs require a sealed chamber and can measure the remaining capacity of the lungs. Air and water plethysmographs can estimate the volume of a particular area of the body. Penile plethysmographs can detect changes in blood flow to the penis and are not considered legal proof of sexual orientation or arousal.
A plethysmograph is a medical device that is used to measure the volume of different parts of the body. It is most commonly used to measure the volume of a specific organ or limb, but it can also measure the body as a whole. Generally, a body or organ will change volume due to a change in the amount of blood or air it contains. There are several types of plethysmographs, including those for lung, respiratory, and penile measurements. Each is used to measure the volume of a different part of the body to help with issues such as air passage restrictions, poor blood circulation, and sexual arousal issues in men.
A lung plethysmograph is used to measure the volume — and therefore the capacity — of the lungs. This requires a sealed chamber and snorkel in most cases, although modern machines sometimes don’t need an enclosed area. The person being tested must then inhale before exhaling as the pressure inside the box is measured. Due to the box being closed off from the outside world, any change in the pressure in the box will be reflected in a change within the lungs. Using this information, lung volume can be calculated using formulas that relate pressure to volume.
In some cases the absolute volume of the lungs may not be important, but the difference between empty and full volume is. For this reason a lung plethysmograph can measure the remaining capacity of the lungs as well as the total capacity to compare the two. The diseases causing the obstruction can be studied using this technique.
An air plethysmograph is used to estimate the volume of a particular area of the body. For example, a leg may be enclosed in a chamber that allows any changes in volume to be detected and measured. Water plethysmographs are similar but are generally more accurate than the air versions. In many cases however, the air is used for convenience although it does not give such reliable results.
Penile plethysmographs are also commonly used to detect changes in volume – and therefore blood flow – to the penis. While the same techniques can’t be used on females, there is a vaginal method called photoplethysmography that can be used to measure blood flow to the area. Some researchers have attempted to use the results of these tastes to demonstrate sexual orientation or different levels of arousal: penile plethysmography is not considered legal proof, however.
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