Long-term Reproducibility of Respiratory Gas Exchange Measurements during Exercise in Patients

27 Feb

Long-term Reproducibility

Present-day technology has greatly facilitated the monitoring of respiratory gas exchange in the clinical exercise laboratory and has provided an im­portant adjunct to the evaluation of patients with stable heart failure. On-line, breath-by-breath meas­urements of oxygen uptake (Vo2), carbon dioxide production (VcOa), and minute ventilation (Ve) are now possible. The monitoring of these variables to­gether with heart rate (HR) and blood pressure (BP) during incremental exercise testing (ie, cardiopulmo­nary exercise testing [CPX]) provides a comprehen­sive, noninvasive assessment of cardiac and ventilatory reserves in patients with heart disease, lung disease, or both. The information derived from these data can be used to do the following: assess the severity of the disease; evaluate the pathophysiologic responses as­sociated with the appearance of exertional dyspnea and fatigue; distinguish ventilatory from cardiac or circulatory impairment; and determine the response to and efficacy of medical therapy.

Despite the growing popularity of CPX, the long- term reproducibility of Vo2, Vco2, Ve, HR, and BP at rest and progressive levels of work has not been evaluated in patients with stable cardiac failure (to our knowledge). Moreover, it is not known whether repro­ducibility is a (unction of the severity of impairment in exercise capacity. Such information would be inval­uable when evaluating the response to, and efficacy of, conventional as well as experimental medical therapy. It was, therefore the purpose of this retro­spective study to quantify the reproducibility of these variables in a group of patients with stable, chronic heart failure of varying severity who had five or more incremental treadmill exercise tests over a period of time that exceeded three months.