What clinical term should be used to document an adolescent experiencing shortness of breath when lying supine?

The clinical term that should be used to document an adolescent experiencing shortness of breath when lying supine is orthopnea. Orthopnea specifically refers to difficulty breathing that occurs when lying flat, which often improves when the person sits up or is in an upright position. This condition is commonly associated with heart failure or other pulmonary issues that can cause fluid to accumulate in the lungs, leading to breathing difficulties when in a supine position.

In contrast, dyspnea is a general term for shortness of breath that can occur in various positions, while apnea refers to the absence of breathing for a period of time. Tachypnea indicates an increased respiratory rate but does not specifically relate to position-related breathing difficulties. Thus, orthopnea is the most precise term to describe shortness of breath when lying flat, making it the correct answer in this context.