1 Department of Anesthesiology, University of Colorado School of Medicine, Aurora, CO, USA. Colby.Simmons@cuanschutz.edu.
2 US Anesthesia Partners of Colorado, Denver, CO, USA.
3 Center for Innovative Design and Analysis, Department of Biostatistics and Informatics, University of Colorado-Anschutz Medical Campus, Colorado School of Public Health, Aurora, CO, USA.
4 Department of Anesthesiology, University of Colorado School of Medicine, Aurora, CO, USA.