Pathophysiology and clinical evaluation of the patient with unexplained persistent dyspnea.

INTRODUCTION: Dyspnea is a complex symptom, which largely results from an imbalance between an afferent sensory stimulus and the corresponding efferent respiratory neuromuscular response. In addition, it is heavily influenced by the patient's prior experiences and sociocultural factors. AREAS COVERED: The diagnostic approach to these patients requires a graded, systematic, and often multidisciplinary approach to determine what is the underlying pathophysiologic process. Utilization of objective data obtained through lab testing, imaging, and advanced testing, such as cardiopulmonary exercise testing, is often required to help identify underlying pathology contributing to a patient's symptoms. This article will review dyspnea's underlying pathophysiological mechanisms and standardized approaches to diagnoses. In the expert opinion section, we will discuss our own clinical approach to evaluating patients with persistent dyspnea. EXPERT OPINION: Unexplained dyspnea is a challenging diagnosis that occurs in patients with and without underlying cardiopulmonary diseases. It requires a systematic approach, which initially uses clinical evaluation in addition to standard imaging and clinical biomarkers. When diagnoses are not made during the initial evaluation, subsequent tests can include cardiopulmonary exercise test and methacholine challenge. To be certain of the correct diagnosis, It is imperative that the clinician determines dyspnea's response to a particular therapeutic intervention.