Coefficient of variation of R-R intervals in severe brain damage

The coefficient of variation of R-R intervals (CVRR) was studied in 18 children having severe brain damage with a mean ± standard deviation (S.D.) age of 8.4 ± 5.9 years, who were divided into ten patients complicated with respiratory insufficiency (RI group) and eight patients with severe athetotic cerebral palsy (SA group). CVRR was obtained in the resting supine position, and was compared with that in 22 neurologically normal controls. CVRR in the RI group (mean ± S.D., 2.19 ± 1.28%) was significantly lower than that in controls (5.56 ± 1.53%), while CVRR in the SA group (11.30 ± 3.91%) was significantly higher than that in controls (both P< 0.01, ANOVA). In particular, the four patients with brain death showed extremely low CVRR of 1.00–1.29%. Since CVRR was 4.09% in the patient aged 4 years with birth injury of the upper cervical spinal cord causing absence of spontaneous respiration, the extremely low CVRR in patients with brain death may be directly related to brainstem dysfunction. The cause of the high CVRR in the SA group was not determined. Thus, CVRR may be useful for quantitative evaluation of severe neurological disorder.