Why is Helium considered a good washout gas?

Helium is considered a good washout gas primarily due to its properties as an inert gas, meaning it does not chemically react with oxygen or other gases in the lungs. When used in medical settings, helium does not get absorbed into the bloodstream, making it an effective choice for displacing other gases within the respiratory system, particularly in situations where reducing air trapping or facilitating smoother gas exchange is desired.

This characteristic allows for efficient ventilation and can help in clearing out stagnant gases from the lungs. Since helium remains in the airways without being absorbed, it aids in achieving better overall gas exchange by allowing other gases, such as carbon dioxide, to be expelled more effectively. This makes helium particularly useful in procedures designed to assist individuals with compromised lung function or those experiencing conditions such as asthma or chronic obstructive pulmonary disease (COPD).

The other options do not accurately describe helium’s action or relevance within pulmonary function. For instance, helium does not react with oxygen to enhance lung function or stimulate breathing, nor does it increase the partial pressure of oxygen in the alveoli. Its primary benefit lies in its inert nature and lack of absorption, making it a safe choice for medical gas administration.