While completing the cardiovascular system health history, a client reports difficulty falling asleep unless she is in an upright position. Which of the following potential problems should the nurse further investigate?

A. Chest pain: This symptom is important but does not specifically correlate with difficulty sleeping unless upright. B. Orthopnea: Difficulty breathing while lying flat (orthopnea) is typically associated with heart failure and would require further investigation to understand its impact on the client's sleep. C. Edema: While edema can be a sign of cardiovascular problems, it does not directly explain the difficulty in sleeping unless in an upright position. D. Palpitations: Palpitations might affect sleep but are less directly linked to the need to sleep upright compared to orthopnea.