Data from each sensor will be downloaded and blood glucose values obtained using proprietary software from Medtronic. Because the CGMS system records glucose readings every 5 minutes capillary or arterial glucose samples obtained will be compared with the closest CGMS reading within 2.5 minutes of the time the sample was obtained. This will generate a set of paired glucose levels for analysis. If the sample falls immediately between 2 readings the later of the CGMS readings will be used to minimize the effect of the lag time for interstitial glucose.