Questions were based on an interview guide developed by P.F. and M.B. and were intended to be open-ended to gain more in-depth responses. Demographic data collected included age, gender, specialty, and number of years in practice. Interviews were approximately 40 min long on average and were audio-recorded. No repeat interviews were carried out. Interviews were transcribed by P.F. from August 2015 to November 2015. Transcripts were not returned to participants for comment or correction. The complete list of interview questions is attached as Additional file 1.