[Cardiopulmonary parameters in hyperthyroidism]

Abstract

Background: Hyperthyroid patients often suffer from impaired exercise capacity with dyspnoea. Two well established, non-invasive methods were used to evaluate the influence of hyperthyroidism on cardiopulmonary function.

Patients and methods: In 42 patients with hyperthyroidism we performed spirometry and cardiopulmonary exercise testing before and after 7 days of propranolol therapy as well as in euthyroidism.

Results: In hyperthyroidism reduced vital capacity and 1-second capacity were observed (95.5 +/- 2.4% vs 102.6 +/- 1.5%; p = 0.0087; 89.4 +/- 2.3% vs 95.2 +/- 2.2%; p = 0.0179). No changes showed during beta-blockade. At the anaerobic threshold reduced tidal volume and enhanced respiratory frequency were noted (1119.8 +/- 48.9 ml vs 1289.3 +/- 62.7 ml; p = 0.0227; 28.3 +/- 0.8 vs 25.4 +/- 0.9; p = 0.0012). A significant tachycardia could be shown. Impaired response to exercise in pulse and respiratory frequency were observed. Work at the anaerobic threshold was impaired in hyperthyroidism (70 +/- 5 watts vs 86.9 +/- 5.7 watts; p = 0.016) and did not change during propranolol therapy. Oxygen pulse at the anaeorbic threshold was reduced in hyperthyroidism (7.7 +/- 0.4 ml O2/beat vs 9.1 +/- 0.4 ml O2/beat; p = 0.0012) and increased with propranolol (8.9 +/- 0.4 ml O2/beat; p = 0.0001).

Conclusion: In hyperthyroidism significant changes in cardiopulmonary function were noted at rest and exercise. High resting function and impaired response to exercise suggest a cardiopulmonary work with low efficiency. Propranolol leads to economization and lowers patients complaints.