Prediction of vestibulo-autonomic symptoms during the caloric test: Evaluation of autonomic activity by spectral analysis of the electrocardiographic R-R interval

Conclusion. If the high-frequency (HF) component of the R-R interval spectrum of the electrocardiogram (ECG) increases after the first stimulation during a bithermal caloric test, subsequent repeated stimulations may be likely to induce autonomic symptoms such as nausea. Objective. Nausea often occurs as a vestibulo-autonomic symptom during the caloric test. However, there have been only a few clinical studies of autonomic activity during this test. To determine whether certain factors can predict the development of nausea, we performed an autonomic function test by means of R-R interval spectral analysis of the ECG during caloric testing. Material and methods. The study subjects were 53 healthy volunteers aged 22-39 years (41 males, 12 females; mean age 25.3 years) and a 35-year-old male patient with a labyrinthine defect. The caloric test was performed in 43 subjects using an air caloric apparatus with bithermal stimulation of alternate ears. After each stimulation, the subjects were asked about autonomic symptoms. Serial ECG records were obtained and R-R interval spectral analysis was performed. Results. Severe nausea was observed in 12 subjects (28%). In the group with severe nausea, the HF component of the R-R interval spectrum increased after the first caloric stimulation when autonomic symptoms had not yet become marked.