Sarcoidosis: the value of exercise testing

STUDY OBJECTIVES

To evaluate exercise testing for the assessment of the extent of pulmonary disease in patients with sarcoidosis.

DESIGN

Retrospective analysis of consecutive patients with sarcoidosis referred to the Pulmonary Physiology Laboratory between 1992 and 1997, who completed at least 6 min of progressive bicycle exercise. Resting and exercise pulmonary function measurements were compared to radiographic stage of disease.

SETTING

Pulmonary Physiology Laboratory at Washington, DC, Veterans Affairs Medical Center.

PATIENTS

Forty-eight outpatient veterans with biopsy specimen-proven sarcoidosis.

RESULTS

Across all radiographic stages of sarcoidosis, total lung capacity, resting diffusing capacity, and exercise gas exchange measurements had a significant variance with radiographic stage. Across the early radiographic stage disease (stages 0 to 2), the change in alveolar-arterial oxygen pressure gradient between rest and exercise, normalized for oxygen uptake, was the most significant measurement in its variation with radiographic stage.

CONCLUSIONS

Changes in gas exchange with exercise may be the most sensitive physiologic measurements to assess the extent of disease in early radiographic stages of sarcoidosis.

Lack of effect of increased inspired oxygen concentrations on maximal exercise capacity or ventilation in stable heart failure

Recent uncontrolled studies have suggested improved maximal exercise capacity and decreased exercise ventilation in heart failure after administration of increased inspired oxygen concentrations. To study the responses further, 16 patients performed staged, symptom-limited cycle ergometry with humidified 21% and 60% inspired oxygen concentrations using a randomized, double-blind, crossover study design. Serial measurements of minute ventilation, heart rate, blood pressure, leg blood flow, and arterial and venous lactate and oxygen content were obtained. Exercise time did not change between the 2 tests (595 +/- 179 seconds and 602 +/- 181 seconds for 21% and 60% oxygen concentrations, respectively). Similarly, measurements of the ventilatory response to exercise and of leg blood flow were not different between the 2 oxygen concentrations. Although hemoglobin oxygen saturation increased from 96.7 +/- 2.1% to 97.9 +/- 1.5% at rest, at both rest and maximal exercise there was no statistically significant difference in arterial or venous oxygen content. This study failed to demonstrate any physiologic or functional benefit from the administration of increased oxygen concentrations to patients with stable heart failure.

Interpretive algorithms for the symptom-limited exercise test: assessing dyspnea in Persian Gulf war veterans

Interpretation of symptom-limited exercise testing requires analysis of a large body of simultaneously recorded cardiopulmonary data. Karlman Wasserman has recommended an algorithmic approach to interpretation (WA) that leads to a dichotomous choice between pulmonary and cardiovascular impairment. An alternative algorithm published by William Eschenbacher (EA) provides for concurrent assessment of cardiovascular and pulmonary exercise impairment. We analyzed a group of 29 individuals referred to the Pulmonary Physiology Laboratory at the Washington Veterans Affairs Medical Center for evaluation of dyspnea following service in the Persian Gulf War to assess the concordance of the two algorithms in determining the cause of dyspnea and exercise impairment in these individuals. They each performed a progressive, ramped, symptom-limited exercise test on a bike for a minimum of 6 min. Exercise measurements were analyzed by both interpretive algorithms. Concordance was found in 28% of tests. The greatest discordance occurred in identifying pulmonary limitation. Eleven had pulmonary limitation by EA; of these, WA found 1 to have pulmonary limitation, 5 to be normal, 4 indeterminate, and 1 musculoskeletal limitation. Of the 11 with pulmonary limitation by EA, but not by WA, 5 had abnormal resting pulmonary function measurements. Analysis of the differences between these two interpretive approaches is given. The EA algorithm may be more sensitive for detecting exercise impairment of pulmonary origin, but its specificity remains to be determined.

Mycobacterium szulgai pulmonary infection: the importance of knowing

A man with a clinical and roentgenographic picture of relapsing M tuberculosis pulmonary infection was subsequently found to have M szulgai infection. This case shows the importance of species identification and susceptibility determinations.