Multi-modal pain measurements in infants
A non-invasive integrated method was developed to measure neural and behavioural responses to peripheral sensory and noxious stimulation in human infants. The introduction of a novel event-detection interface allows synchronous recording of: (i) muscle and central nervous system activity with surface electromyography (EMG), scalp electroencephalography (EEG) and near-infrared spectroscopy (NIRS); (ii) behavioural responses with video-recording and (iii) autonomic responses (heart rate, oxygen saturation, respiratory rate and cardiovascular activity) with electrocardiography (ECG) and pulse oximetry. The system can detect noxious heel lance and touch stimuli with precision (33 μs and 624 μs respectively) and accuracy (523 μs and 256 μs) and has 100% sensitivity and specificity for both types of stimulation. Its ability to detect response latencies accurately was demonstrated by a shift in latency of the vertex potential of 20.7 ± 15.7 ms (n = 6 infants), following touch of the heel and of the shoulder, reflecting the distance between the two sites. This integrated system has provided reliable and reproducible measurements of responses to sensory and noxious stimulation in human infants on more than 100 test occasions.