Richard L. Pardy

Cardiac output at rest and in exercise in elderly subjects.

We measured cardiac output (Q), at rest and during graded exercise, in 68 women and 41 men over the age of 55 yr, using a CO2 rebreathing method. Mean (+/- SD) age was 66 +/- 5 yr in women and 66 +/- 6 yr in men. Only subjects with no history or physical examination findings of pulmonary, cardiac, neuromuscular, or endocrine disease and normal electrocardiography and spirometry were studied. We found a linear relationship between Q and oxygen uptake (VO2) in males and females. The regression equation expressing this relationship in males was Q = 2.9 + 5 VO2 1.min-1 (SEE 2.8) and, in females, Q = 2.9 + 4.6 VO2 1.min-1 (SEE 2.8). This is similar to the relationship previously estimated for elderly males using the direct Fick method and concurs with other reports in the literature which show that, while the Q-VO2 relationship in the elderly has a slope similar to that in younger groups, the Q-VO2 intercept is lower. This means that the absolute level of cardiac output for a given level of work is lower in the elderly than in younger populations. This may reflect an age-related decrease in active metabolic tissue in the elderly and/or altered metabolic regulation with increased oxygen extraction from blood.

Exercise testing in the assessment of pulmonary disease

In this chapter, the different types of exercise tests and the indications for requesting a particular type of test have been discussed. The normal physiological responses to exercise have been reviewed and examples of the abnormal responses seen in a variety of disease states have been discussed. The relatively small number of these responses limits the specificity of exercise tests in actually establishing a diagnosis, but can be helpful in narrowing the differential diagnosis.Perhaps exercise tests are most valuable in cases where the patient’s symptoms are mainly limited to exercise and where investigations done at rest have failed to resolve a diagnostic question. When exercise testing is used under these circumstances, it serves a unique function in the diagnosis and management of pulmonary disease.