What condition triggers dyspnea when a person is lying flat?

Orthopnea is the condition that triggers dyspnea when a person is lying flat. This phenomenon occurs because lying flat can increase pressure on the diaphragm and lungs, thereby making it more difficult for some individuals—particularly those with heart failure or certain pulmonary conditions—to breathe comfortably. In these cases, individuals may experience a sensation of breathlessness that prompts them to seek a more upright position for relief.

In contrast, apnea refers to a temporary cessation of breathing and isn't characterized by dyspnea associated with body position. Bradypnea is defined as an abnormally slow rate of breathing, while hyperpnea involves an increased depth and rate of breathing, neither of which are specifically connected to the positional trigger of dyspnea as orthopnea is. These distinctions help clarify why orthopnea is uniquely tied to experienced symptoms when lying flat.