The Science Journal of the American Association for Respiratory Care

1997 OPEN FORUM Abstracts

The 'Shocking Truth' in a Pulmonary Function Lab: How To Get to the Bottom of Unexplained Dyspnea

Fernando Martinez, MD, Monday, December 8, 1997.

Dyspnea is a common clinical symptom which often provokes extensive medical evaluation. Aggressive use of the pulmonary function laboratory is warranted as most patients presenting with this symptom will have pulmonary disease. As cardiovascular disease encompasses the second most common source of unexplained dyspnea, cardiopulmonary exercise testing (CPET) can frequently prove diagnostic. In a recent series, the value of maximal CPET in 50 sequential patients with unexplained dyspnea was examined. Cardiac disease was identified in 7/50, pulmonary disease in 17/50 and obesity or deconditioning in 14 of 50. CPET was valuable in suggesting pulmonary disease. In the absence of diagnostic EKG changes, it was difficult to differentiate between deconditioning and cardiac disease in patients with unexplained dyspnea. Furthermore, recent reports have described abnormalities of peripheral oxygen utilization which may simulate individuals with cardiovascular disease or severe deconditioning.

Most authorities have suggested the use of CPET in the evaluation of patients with dyspnea unexplained by history, physical examination, routine laboratory studies (CBC, thyroid function tests, EKG, CXR) and nondiagnostic pulmonary function testing. There may be little need to sample arterial blood during CPET while evaluating dyspnea if the DLCO is greater than 70% of predicted although others have suggested that invasive measurements (lactic acid and ABG) may alter the interpretation of CPET in 30% of cases evaluated with CPET for unexplained dyspnea. Further data are required to clarify the role of such invasive testing as routine.

AARC 50th Anniversary, December 6 - 9, 1997, New Orleans, Louisiana.

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