Evaluation of exertional dyspnea in the active duty patient: The diagnostic approach and the utility of clinical testing

Military Medicine, Apr 2002 by Morris, Michael J

Introduction: Minimal information currently exists on how clinicians should approach the evaluation of the young patient with exertional dyspnea. The objective of this study was to determine the frequency of specific diseases and the most useful tests to establish the diagnosis in an active duty military population presenting with exertional dyspnea. Methods: A total of 105 active duty military patients with complaints of exertional dyspnea and 69 active duty military asymptomatic controls were evaluated at a pulmonary disease clinic at an Army tertiary care center. All patients and controls underwent a standard evaluation that included history, physical examination, chest radiography (CXR), arterial blood gas testing, laboratory testing, full pulmonary function testing (PFT), inspiratory and expiratory pressure determinations, methacholine challenge testing, cardiopulmonary exercise testing, electrocardiography, and echocardiography. Results: Obstructive lung disease was found in 52% of patients (35% with exerciseinduced asthma and 12% with asthma), 10% had vocal cord dysfunction, and 14% had other diagnoses. Twenty-four percent of patients had no specific diagnosis. Methacholine challenge testing yielded a positive diagnosis in 41% of patients and spirometry in 16%. Other pulmonary tests were of limited value, with abnormal values of 11.4% for full PFT, 2.9% for arterial blood gas testing, and 0.4% for CXR. Laboratory evaluation yielded positive results in less than 5% of patients, and cardiac evaluation was normal in all patients. Conclusions: Various forms of obstructive lung disease and vocal cord dysfunction were the most common findings in this group. The routine use of spirometry and bronchoprovocation testing is warranted, but other tests, such as full PFT, CXR, and cardiac and laboratory evaluations, have limited diagnostic value in this population.

Introduction

Exertional dyspnea is a frequent complaint for which active i duty soldiers are referred to military pulmonary clinics for evaluation. In general, these patients tend to be young soldiers who have been sent from their respective troop medical clinics for inability to pass the Army Physical Fitness Test (APFT 2-mile run. The ability to pass the APFT run is integral to the retention and promotion of these soldiers.

Exertional dyspnea is a common complaint in the general population because it is a manifestation of a wide variety of illnesses. Several studies have specifically investigated the causes of chronic dyspnea to determine the prevalence of certain disease processes. In 100 consecutive patients referred to a pulmonary disease clinic for evaluation of chronic dyspnea, the following frequency of disease was noted: asthma (25%), interstitial lung disease (12%), chronic obstructive pulmonary disease (12%), cardiomyopathy (9%), upper airway disease (7%), deconditioning (4%), gastroesophageal reflux (4%), psychogenic causes (4%), extrapulmonary causes (3%), and other (5%).1 It is notable that obstructive lung disease, interstitial lung disease, and cardiomyopathy accounted for approximately two-thirds of the causes of chronic dyspnea in that pulmonary clinic.

Another study prospectively evaluated the causes of unexplained dyspnea over a 7-year period.2 All patients had dyspnea for at least 1 month with the cause unidentified by initial history, physical examination, chest radiography (CXR), and spirometry. They underwent a series of standard laboratory tests to include arterial blood gas testing (ABG). In addition, other studies, such as pulmonary function testing (PFT), radiographic tests, and other invasive tests, were performed as indicated. Seventy-two patients were enrolled in the study, and the cause of dyspnea was reported as follows: respiratory tract disease (36%), cardiac disease (14%), hyperventilation (19%), metabolic abnormalities (4%), gastroesophageal reflux (4%), deconditioning (3%), and unexplained (19%). The authors concluded that with the exception of bronchoprovocation testing, the diagnostic yield of any single noninvasive test was poor because of the large number of different diagnoses found. Furthermore, a normal arterial-alveolar (A-a) gradient essentially eliminated occult parenchymal or pulmonary vascular disease.2

Our study was designed to determine the frequency of various disease processes in a young military population. Individuals seeking admission to the military undergo a medical evaluation before entry. Conditions such as asthma, congenital pulmonary or cardiac disorders, and blood disorders, when identified, result in disqualification. Because the screening evaluation consists primarily of history, physical examination, complete blood count, and urinalysis, we expected our patients to have conditions that were acquired after entry or mild enough not to be detected by this screening evaluation. We further anticipated that mandatory regular physical training and having to pass the APFT might result in the detection of disease at an earlier and milder phase compared with other settings. Although we were unsure what disease frequency would be found, we suspected that the diagnoses might be different from those of the more general pulmonary clinic population cited in the studies described above. Our goals in this study were to determine the causes of exertional dyspnea in active duty soldiers and to design the most effective testing sequence to make these diag