1 Department of Otolaryngology and Head and Neck Surgery, Waikato Hospital, Hamilton, New Zealand.
2 Department of Surgery, Waikato Clinical Campus, The University of Auckland, Auckland, New Zealand.
3 Waikato Institute of Surgical Education and Research, Hamilton, New Zealand.
4 Department of Epidemiology and Biostatistics, School of Population Health, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand.