What describes blockage of the canal between the external environment and the ear drum?

The blockage of the canal between the external environment and the eardrum is accurately described as middle ear barotrauma. This occurs when there are significant pressure changes between the external environment and the space behind the eardrum, commonly experienced during activities such as diving or flying. When the pressure difference is not equalized properly, it can lead to discomfort, pain, and potential damage to the structures of the middle ear.

The condition can result when the Eustachian tube, which connects the middle ear to the back of the throat, becomes blocked and fails to equalize the pressure. This can be due to factors such as inflammation, infection, or mechanical obstruction. Understanding this condition is crucial for divers, as it emphasizes the importance of equalizing pressure to prevent injury and maintain ear health during underwater activities.

The other options listed refer to different physiological conditions not related to the blockage of the canal to the eardrum. For example, nystagmus pertains to involuntary eye movement, pneumothorax involves air in the pleural space affecting lung function, and hypoxia signifies deficient oxygen levels in the body. These concepts do not encompass the specific issue of pressure imbalance and blockage affecting the ear canal.