A delayed ear block results from breathing which of the following for an extended period of time?

A delayed ear block occurs due to changes in pressure within the middle ear, often resulting from differences in atmospheric pressure during activities like ascent and descent. Breathing high percentage oxygen for extended periods can lead to absorption atelectasis in the alveoli of the lungs. This phenomenon may reduce the volume of gases in the lungs and subsequently alter the pressure dynamics throughout the respiratory system, including the Eustachian tubes that connect the throat to the middle ear.

When a person breathes high concentrations of oxygen, the nitrogen levels in the body decrease because nitrogen is displaced by oxygen in the alveoli. Since nitrogen is needed to help maintain normal lung volumes and prevent the collapse of small airways, a significant reduction can create a negative pressure in the lungs and, consequently, influence the pressure in the middle ear. If the pressures in the middle ear cannot equalize due to impaired Eustachian tube function, it may lead to a delayed ear block situation.

Understanding this mechanism is vital as it underscores the importance of managing oxygen levels in aviation and diving environments to prevent barotrauma related issues such as ear blocks.