Deep breath test for evaluation of autonomic nervous system dysfunction in familial dysautonomia

Familial dysautonomia is a genetic disease that affects the sensory and autonomic nervous systems with varying severity. The deep breath test is one of several measures used to assess the severity of autonomic diseases, but its value in familial dysautonomia has not yet been investigated.

To determine the diagnostic value of the DBT in patients with familial dysautonomia.

Eight patients with familial dysautonomia and eight healthy volunteers were examined by electrocardiography for 1 minute at rest and during forced deep breathing. The following values were recorded: maximum expiratory and minimum inspiratory heart rate and the difference between them (deltaE/I), standard deviation of the heart rate values, interbeat intervals, and E/I ratio. Spectral power analysis of heart rate variability was also performed.

The patients with familial dysautonomia showed a lesser change in heart rate in response to the change in breathing pattern than the controls. Mean values in the study group were significantly higher for minimal inspiratory heart rate and significantly lower for deltaE/I, heart rate standard deviation and E/I ratio, indicating a non-flexible heart response and abnormal parasympathetic function. These findings were supported by power spectral analysis.

Patients with familial dysautonomia have significantly disturbed response to physiological stimuli. The DBT may serve as a reliable means to quantify autonomic dysfunction in this patient population.