Respiratory sinus arrhythmia in persons with organic solvent exposure: comparisons with anxiety patients and controls

Persons exposed to organic solvents have psychiatric symptomatology and cognitive impairments. The results of several studies have suggested that some psychiatric symptoms in these patients reflect similar reactions observed in patients with anxiety disorders. Respiratory sinus arrhythmia provides an indication of impaired autonomic functioning. Whereas decreased respiratory sinus arrhythmia has been reported in anxiety patients, investigators have also noted that higher respiratory rates in these patients obscure differentiation of respiratory sinus arrhythmia from normal values. In this study, the authors recorded multiple parameters of respiratory sinus arrhythmia under a paced-breathing condition in 28 patients with solvent exposure, in 18 patients with anxiety disorder, and in 31 controls. The authors observed a high 1-y retest reliability for a subset of the subjects. Significantly reduced respiratory sinus arrhythmia was observed in both anxiety and solvent-exposed patients, compared with controls. Maximum mean heart rates/cycle did not differ among groups, but minimum heart rates were significantly lower for controls than for the two patient groups. The findings suggested that reduced respiratory sinus arrhythmia among patients is not related to higher maximum rates but, rather, to a decrease in vagally mediated alteration associated with respiratory changes observed in both patient groups.