What condition is characterized by regular, shallow breathing occurring over a period of time?

Eupnea is the correct choice because it describes normal, healthy breathing, characterized by regular and unobstructed breaths that are typically of a moderate depth and rate. This type of breathing generally occurs comfortably at rest and allows the body to effectively exchange oxygen and carbon dioxide.

In a clinical setting, eupneic breathing typically falls within a respiratory rate of 12 to 20 breaths per minute for an adult. Recognizing eupnea is important in health assessments, as it indicates that the body is functioning well in terms of respiratory function and does not present any signs of distress or underlying respiratory issues.

On the other hand, conditions like apnea involve the cessation of breathing for a certain period, tachypnea refers to an increased respiratory rate often due to conditions such as fever, anxiety, or respiratory distress, and bradycardia pertains to a slower than normal heart rate, which is not directly related to breathing patterns.