Breathlessness During Exercise: Experience and Memory

Breathlessness, Dyspnea

Breathlessness during exertion is a major limiting factor for patients' physical capacity and activity. Increased exertional breathlessness often results in impaired activity, spiraling deconditioning and further worsening of exertional breathlessness, quality of life and prognosis. Recalled symptoms (from memory) can differ substantially from the actually experienced symptoms.The recall of symptom intensity is affected by several factors including the experienced peak intensity and the intensity at the end of the episode. This 'Peak-end-rule' has been reported in studies of pain, and in breathlessness in daily life and during exercise. A randomized trial reported that adding a time period with decreased pain at the end of a colonoscopy decreased the patient's recalled total pain of the event, improved their overall perception of the event and made them more willing to participate in similar procedures in the future. Pulmonary rehabilitation training is the first line treatment for exertional breathlessness and deconditioning in cardiorespiratory disease. However, the training as well as physical activities of daily life are often limited by the person's perception of his/her capacity, which is based on recalled breathlessness during exertion. The person's predicted breathlessness - that is, the level of breathlessness that the person predicts will occur during a future activity, is likely a major determinant of his/her willingness to participate in training as well as of the level of physical activity in daily life. To improve the effectiveness of cardio-pulmonary rehabilitation training and the patients' health status, new approaches for decreasing the perceived exertional breathlessness and optimize training are needed. The investigators hypothesize that adding a period of lower breathlessness intensity at the end of training might be a way to manipulate the recalled (remembered) symptom intensity during the training, and to improve the subject's perceived future exercise capacity and willingness to participate in physical exercise/ training.

The primary purpose is to test whether adding a period of lower level of exertional breathlessness at the end of an exercise test decreases the overall level of recalled breathlessness for the test. Secondly the investigators aim to evaluate factors that affect the level of recalled breathlessness, and whether decreased exertional breathlessness results in the participant's reporting lower predicted future exertional breathlessness and higher exercise capacity. Information about the study and the pre-test questionnaire will be sent home to patients referred for standard cycle exercise testing. The pre-test questionnaire is completed by the participant at home or before the exercise test. Eligibility is confirmed and written informed consent is obtained for all participants by the investigator before starting the exercise test. All patients included in the RCT (randomized clinical trial), randomizations, and patients included in the observational sub-study are registered in a log file including study ID, Swedish identification number and test date, stored securely at the Department of Clinical Physiology. Standard exercise test is performed according to clinical practice, current international guidelines and guidelines from the Swedish association for Clinical Physiology. Testing is done on bicycle ergometers with small incremental increases in workload every minute. The level of breathlessness is self-reported by the participant each 2 minutes on a modified Borg CR10 (mBorg) scale between 0 (none) and 10 (maximal). The level of perceived exertion is self-reported by the participant on the Borg RPE (rating of perceived exertion) scale between 7 (none) and 20 (maximal), and standard parameters of exercise testing are measured according to clinical routine practice. At the end of the regular exercise test conducted according to clinical practice, with the participant still on the test cycle, a sealed opaque envelope is broken by the staff with a code that randomly allocates the participant in a 1:1 ratio to either an additional 2 minutes of low intensity exercise testing (intervention group), or to no additional testing (control group). During the intervention period. The workload used will be about 50% of the maximal workload but lowered if needed, and assessments are conducted including of breathlessness, perceived exertion, breathing frequency and blood pressure. A period of a few minutes of lower exertion ('cool down') at the end of the exercise test is clinical practice in many laboratories including in the USA, and is not expected to affect the safety or diagnostic properties of the exercise test. As an added precaution the investigators have obtained opinions from well-known experts in cardiac stress testing (Dr. Olle Pahlm and Dr. Paul Kligfield). In additions to this ST loops will also be used to further enhance the diagnostic properties of the test. ST loops are not currently used by default in the study laboratory. A post-test questionnaire is completed by the participant 30-90 min after the exercise test. Patients completing the exercise test who fulfill the inclusion criteria and give their written informed consent are included in an observational longitudinal follow-up study. The study data are cross-linked with medical records and governmental public registries regarding diagnoses, procedures and hospitalizations (National Patient Register) and mortality (Causes of Death Register) with up to 10 years follow-up.

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