Relating Experienced To Recalled breathlessness Observational (RETRO) study: A prospective study using a mobile phone application

Background: Breathlessness, the subjective sensation of breathing discomfort, is common and appears in the daily life of people with cardiorespiratory diseases. Physicians often rely on patient's history based on symptom recall. The relation between recalled and experienced breathlessness is still poorly understood. This paper presents the protocol for a study primarily aimed at evaluating the relationship between experienced breathlessness and (1) recalled breathlessness and (2) predicted future breathlessness. Methods: A mobile phone application will be used to collect data during daily life. Medically stable participants, ≥18 years of age with mean daily breathlessness of Numerical Rating Scale (NRS) 3/10 and able to use a mobile phone with internet will rate their breathlessness intensity on a 0-10 NRS prompted the user several times daily for 1 week. Participants will recall their breathlessness each day and week. Multivariable random effects regression models will be used for statistical analyses. Results: Results of the study will be submitted for publication in peer-reviewed journals and presented at relevant conferences. Discussion: This protocol describes a study aimed at investigating previously unknown areas of the experience and recall of breathlessness using a new method of data collection.