Reproducibility of non-standardised autonomic function testing in the pre-operative assessment screening clinic*

By convention, autonomic function tests are undertaken under standard test conditions that limit their implementation during routine pre-operative assessment. We therefore evaluated the comparability of autonomic function tests under both non-standardised and standardised test conditions in 20 healthy male subjects. Autonomic function was assessed using an ECG monitor and a continuous non-invasive blood pressure measurement device. Under non-standardised conditions, intraclass correlation for heart rate variability analysis was good for the low and high frequency bands (0.87; 95% CI 0.58-0.96 and 0.83; 95% CI 0.56-0.94, respectively), but moderate (0.65; 95% CI 0.14-0.86) for the very low frequency band; reproducibility was high for the expiration/inspiration ratio (0.89; 95% CI 0.71-0.96), Valsalva ratio (0.76; 95% CI 0.37-0.91) and handgrip test (0.76; 95% CI 0.35-0.91) (all p<0.05) but was low for the response to quick standing. Reproducibility under standardised conditions was comparable to the above values. We demonstrated that reproducibility for most autonomic tests under non-standardised conditions is acceptable and suggest that implementation of these tests during pre-operative assessment may be feasible.