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

Persons exposed to organic solvents have psychiatric symptomatology and cog nitive 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 a n indication of impaired autonomic functioning. Whereas decreased respirato ry sinus arrhythmia has been reported in anxiety patients, investigators ha ve also noted that higher respiratory rates in these patients obscure diffe rentiation of respiratory sinus arrhythmia from normal values. In this stud y 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 solve nt-exposed patients, compared with controls. Maximum mean heart rates/cycle did not differ among groups, but minimum heart rates were significantly lo wer for controls than for the two patient groups. The findings suggested th at reduced respiratory sinus arrhythmia among patients is not related to hi gher maximum rates but, rather, to a decrease in vagally mediated alteratio n associated with respiratory changes observed in both patient groups.