In body Plethysmography, a person is asked to expire against a closed glottis. Whiat will be the change in the pressure in the lung and the box
**Core Concept**
Body Plethysmography is a technique used to measure changes in lung volume by sealing a person in a sealed box and measuring the pressure changes within the box and the lungs during breathing maneuvers. The technique relies on the principle of Boyle's Law, which states that the volume of a gas is inversely proportional to the pressure at constant temperature.
**Why the Correct Answer is Right**
When a person expels air against a closed glottis, they are effectively occluding the airway, causing the air within the lungs to compress. According to Boyle's Law, as the volume of the gas (air) decreases, the pressure within the lungs increases. Similarly, within the sealed box, the pressure also increases due to the compression of the air within the box. This increase in pressure within the box is directly proportional to the change in lung volume.
**Why Each Wrong Option is Incorrect**
**Option A:** In this scenario, the pressure in the lung and the box would decrease due to the expansion of the lungs and the box. However, this is not the case when a person expels air against a closed glottis.
**Option B:** This option suggests that there would be no change in pressure within the lung and the box. However, as explained earlier, the compression of air within the lungs and the box would lead to an increase in pressure.
**Option C:** This option is incorrect as it suggests that the pressure within the lung and the box would increase due to the expansion of the lungs and the box, which is the opposite of what occurs when a person expels air against a closed glottis.
**Clinical Pearl / High-Yield Fact**
In body plethysmography, the pressure change within the box is directly related to the change in lung volume, making it an accurate and reliable technique for measuring lung volumes.
**Correct Answer:** C. The pressure within the lung and the box will increase due to the compression of the air within the lungs and the box.