It can be difficult to assess pain in very young and premature infants. Simply watching for changes in posture or expression isn't always enough to indicate how much discomfort a newborn is feeling. Therefore, researchers from University College London were looking for a better way to determine how much pain a baby is feeling.
They used electroencephalography (EEG), electrocardiography (ECG) and electromyography (EMG) to indirectly detect evidence of pain. These non-invasive devices record electrical activity in the brain, the heart and in muscle, respectively. Infants were hooked up to the devices and recordings were made of three events: a heel tap with a rubber bung, a touch with a lancet that did not pierce the skin, and a medically required heel lance to collect blood. EEG, ECG and EMG results were compared for the three events. The electrical data correlated well with presumed pain levels.
Aside from providing information to people who must care for infants, this study is interesting because it was published in the Journal of Visualized Experiments. You can watch a video demonstrating exactly how the experiments were conducted, and what the results were. Warning, the video includes a close up of an infant receiving a heel lance.