Introduction
Breathlessness, the feeling of breathing discomfort, is a cardinal symptom of cardiorespiratory diseases and is strongly associated with adverse health outcomes.1 Breathlessness is linked to reduced physical activity, worsening deconditioning, increased anxiety and depression, impaired quality of life, increased risk of hospitalisation and earlier death.1 2 Breathlessness is associated with worse prognosis across cardiorespiratory diseases3 4 and is a stronger predictor of mortality than the level of airflow limitation in chronic obstructive pulmonary disease (COPD).3 In patients with suspected heart disease undergoing cardiac stress testing, more severe breathlessness is a strong risk factor for earlier death overall and from cardiac disease.5
Breathlessness consists of several different qualitatively distinct sensations that vary in intensity.1 Several dimensions of this symptom can be differentiated by the individual: the experienced intensity and unpleasantness, the associated emotional response and the functional impact on the person’s life.1
Despite its serious impact, breathlessness remains frequently under-reported, unmeasured and insufficiently treated in clinical practice.6 The level of unpleasantness, emotional responses and how the breathlessness feels (sensory qualities (SQs)) have been measured in different studies using different, often disease-specific instruments with varying types of scales, wordings and time frames.1 7 This makes it difficult to compare findings between studies, patient populations and settings. Standardised multidimensional measurement is essential to adequately capture treatment effects in clinical trials as different treatments may target different dimensions of breathlessness.8 9 Opioids have been found to have a stronger effect on the experienced unpleasantness and associated anxiety from breathlessness than on the intensity.8 Patients with COPD with a high level of anxiety and breathlessness-related fear benefit from pulmonary rehabilitation,10 which positively affects the patient’s coping and function in relation to breathlessness rather than the intensity of the symptom.9
The Multidimensional Dyspnea Profile (MDP) is a recently developed tool to separately measure the immediate unpleasantness or discomfort of breathing (A1 domain), presence and intensity of five SQs, and intensity of five emotional responses of breathlessness.7 The MDP was developed to measure breathlessness across underlying diseases and settings (laboratory and non-laboratory).11 12 The MDP builds on extensive mechanistic studies of multidimensional pain and breathlessness.7 The MDP was first tested in response to laboratory stimuli7 and then validated in 151 patients admitted to an emergency department for acute breathlessness (29% had asthma, 27% had COPD, 19% had pneumonia, 13% had heart failure, and 13% had other conditions).11 The MDP has been translated and used in several languages, including French (language-specific versions for France, Belgium and Canada), German, Dutch (language-specific versions for Belgium and the Netherlands), English (language specific versions for Canada and the UK) and Swedish.7 13 14
The MDP can either be administered by an investigator/healthcare provider or be self-completed with a person on hand to answer questions during initial administration.7 The time frame or situation of the measurement is defined by the user.7 Before use, it is important that the respondent receives standardised information and instructions as described elsewhere,7 for a reliable and valid measurement. The MDP consists of 11 items divided into three domains.7 In the first domain, the unpleasantness or discomfort of the breathing sensation is rated on a numerical rating scale (NRS) between 0 (‘neutral’) and 10 (‘unbearable’). In the second domain, the respondent first indicates which of the five descriptions matches their breathing discomfort and indicates the most accurate descriptor. The respondent then rates the intensity of each descriptor (and of another self-specified sensation if needed) on an NRS between 0 (‘none’) and 10 (‘as intense as I can imagine’). In the third domain, the respondent rates the intensity of emotional responses to their breathing discomfort (depression, anxiety, frustration, anger and fright) on an NRS between 0 (‘none’) and 10 (‘the most I can imagine’).7
Validation studies in outpatients have been performed in Australia15 and in France,13 but only for patients with COPD. There is currently no validated instrument for multidimensional measurement of breathlessness in Swedish and no published validation of MDP in outpatients across different cardiorespiratory diseases.
The primary aim was therefore to validate the Swedish translation of MDP in terms of the underlying factor structure, internal consistency, test–retest reliability and concurrent validity in outpatients with cardiorespiratory disease. The secondary aim was to compare the measurement properties between patients with COPD and patients with other cardiorespiratory diagnoses.