Residual Volume Definition
Residual volume is the quantity of air that stays in an individual’s lungs after utmost exhalation (RV). In other words, it is the volume of air we cannot possibly exhale, indicating that our lungs are never completely empty. Otherwise, the tissue would clump together and cause them to collapse. A person’s RV is approximately one litre on average, and doctors could assess it using specialised testing since it can indicate lung health.
Below is a reading using a spirometer, a tool that monitors lung ability. Volume is shown by the vertical axis, while time is represented by the horizontal axis. The RV is the variation between the operational remaining capacity and the expiratory reserve capacity, that is, the maximum amount of air a person can still exhale after a natural exhale.
Measuring the Residual Volume
Because determining residual volume is seldom an easy task. The following tests do not provide a direct answer, but rather strategies for determining the RV indirectly.
Helium Dilution Test
The participant must inhale and exhale via a container containing a specific quantity of helium combined with oxygen. This combination will be used throughout this test, the subject inhales the mixture, and the RV is calculated using the remaining helium concentration in the container.
A complete oxygen inhalation is followed by an exhalation. The difference between zero and the amount of nitrogen released is then utilised to determine the RV (which people’s lungs contain as a result of breathing normal air).
Plethysmography is a test that measures changes in blood volume or air volume. The individual must stay in a sealed compartment and breathe in and out of a sealed mouthpiece, making it difficult to breathe in. To approximate the RV, the change in chamber pressure owing to changes in the individual’s chest wall size is used.
If none of these methods are employed, predictions can be formed by combining a specified percentage of an infant’s weight or vital capacity, or by using the infant’s weight and height.
The Effect of Disease on Residual Volume
Obstructive Lung Diseases
It is difficult for an individual with restrictive pulmonary illness to exhale the same volume of air as a healthy individual. As a result of the surplus air remaining in the lungs after exhalation, the RV is observed to be greater than normal in this scenario.
Restrictive Lung Diseases
The lungs cannot expand to their typical size in restrictive lung disease. Because the movement of air in the airways is not obstructed, we usually detect an ordinary RV.
- Vital capacity:Vital potential is the amount of air an individual can forcefully exhale after taking a maximally pressured inhalation.
- Minute ventilation:Micro ventilation refers to the quantity of air inhaled and exhaled in one minute.
- Inspiratory capacity:After natural exhalation, inspiratory capacity is the highest quantity of air that can be absorbed into the lungs.
- Tidal volume:The amount of air inhaled and expelled spontaneously and without force is referred to as tidal volume.
Question And Answer
1.Which of the following is true of obstructive lung diseases?
- The residual volume is no different from normal
- The diseases don’t allow for full expansion of the lungs
- The residual volume is lower than normal
- The residual volume is higher than normal
D is correct. The residual volume in obstructive lung diseases is higher than normal due to the difficulty of complete exhalation.
2. What is the average amount of residual volume in healthy lungs?
- Two liters
- One liter
- Three liters
- Six liters
B is correct. The average amount of residual volume is one liter, and is generally higher in men.
3. Why is it that we can’t empty out our lungs?
- Due to the amount of nitrogen contained in the air
- Due to air pollution
- The lungs would collapse and not be able to inflate again
- Helium can’t leave the lungs
C is correct. The lungs would collapse as the lung tissues stick together.