Dysfunctional Breathing: Characterisation and Assessment

Breathlessness Clinical Trial

Official title:

Dysfunctional Breathing: Multidimensional Characterisation and Assessment Tool

Clinical Trial Details — Status: Not yet recruiting

Administrative data

• NCT number: NCT03043469
• Other study ID #: 1468-NHS-Dec/2016- 4775-1
• Status: Not yet recruiting
• Start date: August 8, 2020
• Est. completion date: May 30, 2021

Study information

• Verified date: July 2020
• Source: Brunel University
• Contact: Lais S Vidotto, Ms
• Phone: 4401895278024
• Email: lais.vidotto[@]brunel.ac.uk
• Is FDA regulated: No
• Study type: Observational

Clinical Trial Summary

Dysfunctional breathing (DB) is a respiratory condition characterised by an abnormal breathing pattern, among other complaints, that can occur either in the absence of other pathophysiology (primary DB), e.g. anxiety-related factors, or secondary to cardiopulmonary disease (secondary DB), e.g. asthma. As a consequence, patients may experience breathlessness and present with periods of increased ventilation or erratic breathing, interspersed with episodes of breath holding or deep sighs. In addition to respiratory symptoms, DB also generates non- respiratory symptoms (e.g. dizziness and increased heart rate). It is estimated 1 in 10 people in the United Kingdom (UK) have DB. However, DB remains poorly understood, with no standardised approach to diagnosis and assessment.

The purposes of this study are:

Study 1) To identify physiological, functional and psychological characteristics of participants with DB compared to healthy participants.

Firstly, symptoms, lung function, respiratory gas analysis, exercise capacity, respiratory muscle function, respiratory motion, level of physical activity, quality of life and anxiety & depression scores will be assessed in 20 participants with primary DB, 20 with secondary DB and compared to 20 healthy participants.

Study 2) To develop an assessment tool based on physiological, functional or psychological variables found to be different between any of the 3 groups in Study 1.

In order to do that, 54 people with DB (between primary and secondary) and 27 people presenting with breathlessness secondary to restrictive lung disease will be assessed. Analysis of these data will determine whether these variables can be used as a diagnostic tool capable of distinguishing DB from restrictive lung diseases characterised by breathlessness.

The recruitment period will be 1-2 years, with an individual participation of 9 days; 1-day on site testing, plus 7-day home activity monitoring, and 1 day to return the activity monitor (which will happen whenever the participant needs to return to the site).

Description:

In this research, the aims are: 1) to characterise and compare participants with primary dysfunctional breathing (DB), secondary DB and healthy participants, 2) to develop an assessment and identification tool for the population with DB, 3) to identify subgroups of people with DB based on their functional, physiological and psychological characteristics.

In order to do that, in Study 1, there will be a comparison of many different aspects (described below) between three groups of 20 participants each: primary DB, secondary DB and healthy participants. With the results of these comparisons, it will be possible to know more about the differences people with DB have in relation to the healthy population, and to describe their main characteristics. Based on that, in Study 2, it will be possible to select the variables that are different between groups and replicate those tests in an extra 54 participants DB (primary and secondary) and 27 with breathlessness secondary to restrictive lung disease (DB excluded). The second stage will suggest tests to be used when identifying and evaluating this population, and statistically identify subgroups of people with DB based on their characteristics.

It is important to note why the inclusion of healthy participants and participants with breathlessness secondary to restrictive lung disease is important in this research programme. Firstly, it is essential to know the main characteristics of DB in relation to the healthy population. Secondly, the assessment tool has to be able to suggest probability of negative diagnosis of DB for people who do not have DB, and not only positive diagnosis for those who have.

There are no standardised criteria available to diagnose DB. However, experienced chest physicians at Guy's and St Thomas' Foundation Trust (GSTFT) identify probable DB, and provide a clinical diagnosis (CD) according to the following criteria: patients presenting with symptoms that are not concordant with the severity of the underlying health condition (in case of secondary DB), patients presenting with symptoms that persist despite optimal disease management and/or no objective markers of deterioration/exacerbation (in case of secondary DB), patients presenting with symptoms in the presence of negative tests for organic cause/medically unexplained (in case of primary DB), patients presenting with symptoms that are considered functional (in case of primary DB).

Ability to comprehend and/or perform the procedures of this research, as well as the presence of major orthopaedic, neurological or cardiac conditions will be checked by Leyla Osman and the Chest physicians via medical records and when the possible participant is approached to receive information about the study. For example: health conditions in which patients present with an impairment of mental faculties and/or motor function (inability to cycle with no discomfort).

Healthy participants will be contacted via email list at Brunel University London, and via flyers placed on the University's and Hospital's website and murals (attached). Participants with restrictive lung disease will be reached in person or via telephone call when they are referred to respiratory physiotherapy, or via flyers placed on the Hospital's murals. Because there are not plenty of patients with DB, those who are already registered on the Hospital's system as presenting with DB (assessed by a chest physician) will be called. New patients with DB will be contacted in person or via telephone call by the respiratory physiotherapist of the clinical team (Leyla Osman).

If those contacted about this research are interested in taking part in this study, they will be provided with the participant information sheet, have the opportunity to ask any questions they may have and it will be checked if they meet the inclusion criteria. Before starting the assessments, they will be asked to sign the informed consent.

When signing the informed consent, participants will be asked a few questions:

Please, tick this box if you authorise the researchers of this study to have access to your medical records Please, tick this box if you are aware that your General practitioner will be informed about your participation in this research Please, tick this box if you would like to receive a report with your results of the tests performed in this study (within 30 days from the end of your assessments) Please, tick this box if you would like us to contact you in the future to inform you about the final results of this study Please, tick this box if you are participating in other study/ies at this moment. If yes, please mention below what this/these study/ies is/are about and the contact of the person responsible for it The assessments will be performed by Lais Silva Vidotto (respiratory physiotherapist and researcher) at the Hospital/University over a period of approximately 3 hours. Many of these assessments form part of routine hospital investigations for patients with DB. Duration may vary depending on individual needs and limitations, such as time given to recover from any physical or mental effort. Secondly, a physical activity monitor will be given to all participants, which will be returned to the researchers on the next medical appointment at the Hospital/classes at the University (classes at the University in case of healthy participants). During the 3-hour assessment they will have the opportunity to rest whenever is necessary and snacks and refreshments will be provided in the intervals (caffeine-free ingredients).

Assessments and their approximate duration are as follows: demographic information (10 minutes), health-related quality of life questionnaire (SF-36) (5 minutes), Hospital anxiety and depression scale (HADS) (5 minutes), Nijmegen questionnaire (NQ) (5 minutes), Self-evaluation of breathing questionnaire (SEBQ) (5 minutes), Asthma Questionnaire (only for asthmatics) (5 minutes), lung function test (30 minutes), respiratory muscle function (30 minutes, assessment of the respiratory movements (MARM) (10 minutes), breath-hold test (BHT) (20 minutes), slow-breathing task (15 minutes) and the sub-maximal exercise test (10 minutes) (during the two last tests participants will be wearing small and light-weight devices that monitor heart activity, breathing function and blood pressure and take 15 minutes to be placed all together).

Day 1: Hospital assessments (~3 hours) The tests will be performed in a private room at St Thomas' Hospital or Brunel University London. Participants will be advised to stay 48 hours without practicing exercise. Also, they will be instructed to take all the medicines they normally use and to report their names and doses to the examiner.

1. Patients will be asked about their medical history, date of birth and symptoms. Also, participants' weight and height will be measured.

2. Chest movements while breathing:

At this stage, participants are going to stand still while the researcher will place their hands on the back of their chests in order to evaluate its movements while participants are breathing. This is going to take about 10 minutes.

3. Slow-breathing task:

Participants will be instructed on how to breathe slower (6-10 bpm) for a few minutes (5-15 minutes) and will keep wearing the mask, the heart rate monitor and the arterial blood pressure monitor during this task.

4. Exercise test, breathing and cardiovascular function:

Light-weight devices will be attached to participants' chest (cardiac monitor), in order to evaluate heart function, to their faces (mask-gas analyser) to assess respiratory function, and to their non-dominant arm (arm and finger), to assess blood pressure. The device used to assess blood pressure continuously measures the pulse of the finger, calibrated by an arm cuff, with no discomfort to the participant. Those assessments will be performed while participants rest for five minutes, while they cycle on a bicycle with moderate resistance for six minutes, and while they rest for five more minutes. Just before the exercise test, at the third minute, and just after it, participants will be asked about any leg or breathing discomfort and how mindful they are in relation to discomfort related to the task. Approximate time of this task: 16 minutes.

5. Questionnaires:

Participants will be asked to fill in some questionnaires that will ask about their breathing and quality of life and will take about 25 minutes to complete. Participants will be asked to complete these questionnaires after having the opportunity to ask questions about them.

6. Breath hold test:

Participants will be asked to hold their breath for as long as they can for 3 times, resting for 5 minutes after each one of them, and the researcher will use a stopwatch in order to count the time they are able to do it. The whole task will last in approximately 20 minutes.

7. Lung and respiratory muscle function assessments:

Researchers will use three devices to measure the function of participants' lungs and respiratory muscles. They will be asked to breathe in and out in several different ways, wearing a nose clip, so that researchers can record their general breathing function. This is going to take about one hour to finish.

At the end of the assessment session, participants will be instructed on how to use a device that measures the level of physical activity.

Days 2-8: Physical Activity Monitoring Participants will be asked to wear two small activity monitors attached to their hip for 7 consecutive days, keeping their routine as normal as possible. Participants will have to use the equipment for at least 8 hours/day while they are awake, excluding water activities (e.g. shower) and sleeping, writing down the exact time they put it on and the time they took this off.

Day 9: Return of the activity monitors Participants recruited from Brunel University London will return their physical activity monitors to the researchers on their next visit to the University (for classes, meetings etc.); those recruited from GSTFT will return it on their next hospital appointment.

Although this study requires a cross-sectional design, it may take a long period to be completed, since patients with DB are not easily identified and referred to other health professionals to receive specific diagnosis or treatment. Considering this difficulty in finding participants with DB, justified by the fact that there is no established way of identifying these patients, this research may take 1-2 years to be completed. However, It will enable the researchers to look at every single result and be rigorous with the quality of the data collected. In order to do that, the researchers will not wait for all assessments to be finished to process and plot the data. Every time a participant is evaluated, their results will be organised and plotted within the next few days. It will also enable the data to be statistically analysed when needed.

Recruitment information / eligibility

• Status: Not yet recruiting
• Enrollment: 141
• Est. completion date: May 30, 2021
• Est. primary completion date: April 30, 2021
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: All
• Age group: 18 Years and older

Eligibility

Inclusion Criteria:

• patients with DB (according to the CD)

• healthy people

• aged 18 or over,

• must be able to comprehend and/or perform the procedures of this research

• must be able to consent to participate

• people with signs of breathlessness secondary to restrictive lung disease (DB excluded)

Exclusion Criteria:

• people whose condition is unstable or have experienced an exacerbation of symptoms over the last 4 weeks

• patients who are oxygen-dependant (at rest or during exercise),

• those who are on oral steroids or have completed a course of those medications less than four weeks prior to the assessment day,

• those who have major orthopaedic, neurological or cardiac conditions

• those who received breathing retraining before

Related Conditions & MeSH terms

• Breath Shortness
• Breathlessness
• Dyspnea
• Hyperventilation
• Hyperventilation Syndrome
• Respiration Disorder
• Respiration Disorders
• Respiratory Aspiration

Intervention

Other:
• Short-form survey instrument
Questionnaire with questions about quality of life. Takes about 5 minutes to be completed.
• Demographic data
height, weight, age, gender, list of comorbidities, health history, level of physical activity, medicines in use. Takes about 10 minutes to be completed.
• Hospital Anxiety and Depression Scale
Questionnaire with questions about anxiety and depression. Takes about 5 minutes to be completed.
• Nijmegen questionnaire
Answering questions about symptoms related to breathing. Takes about 5 minutes to be completed.
• The Self-evaluation of breathing questionnaire
Answering questions about self-evaluation of breathing. Takes about 5 minutes to be completed
• six-minute exercise test
Cycling against certain load in a bicycle for 6 minutes. Takes about 16 minutes to be completed together with indirect calorimetry, oxygen saturation monitoring, heart rate variability analysis and continuous monitoring of arterial blood pressure).
• Indirect calorimetry
Breathing through a mask that measures levels of oxygen, carbon dioxide, breathing frequency and others (non-invasively). Takes about 16 minutes to be completed, together with the 6-minute exercise test.
• Oxygen saturation monitoring
The measurement of the amount of oxygen which is attached to haemoglobin molecules (non-invasively). Takes about 16 minutes to be completed, together with the 6-minute exercise test.
• Heart rate variability analysis
Measurement of the variation in the beat-to-beat interval (non-invasively). Takes about 16 minutes to be completed, together with the 6-minute exercise test.
• Continuous measurement of arterial blood pressure
Measurement of blood pressure based on the peripheral pulse using a finger cuff (non-invasively). Takes about 16 minutes to be completed, together with the 6-minute exercise test.

Diagnostic Test:
• Lung function test
Breathing through a mouth-piece in many different ways in order to measure the function of the lungs (non-invasively).

Other:
• Respiratory muscle function
Breathing through a mouth-piece in many different ways in order to measure the function of the respiratory muscles (non-invasively).
• Manual assessment of respiratory motion
Measure of the movements of the thorax while the participant is breathing (non-invasively).
• Breath-hold test
Holding the breath a few times for as long as possible.
• Physical Activity monitoring
Wearing a light-weight activity monitor to be wore on the hip for 7 consecutive days during, at least, 8 hours per day.
• Asthma Control Questionnaire
Only for asthmatics: answering questions about the control the participant has over this respiratory condition/symptoms.

Locations

Country	Name	City	State
United Kingdom	Brunel University London	London	Middlesex

Sponsors (2)

Lead Sponsor	Collaborator
Brunel University	University of Sao Paulo

Country where clinical trial is conducted

United Kingdom, 

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* Note: There are 64 references in all — Click here to view all references

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Signs of Anxiety and Depression	Anxiety and depression will be evaluated by the widely used Hospital Anxiety and Depression Scale (HADS), developed by Zigmond and Snaith (1983) to identify and screen cases of anxiety and depression in non-psychiatric environments. It has been proven to be a valid psychological instrument (Bjelland et al. 2002). The HADS is subdivided into two subscales with seven questions each: Anxiety (HADS-A) and Depression (HADS-B). Therefore, it is able to differentiate anxiety from depression possible/probable disorders.	This scale will be applied only once during the first day of assessment and takes about 5 minutes for the participant to complete.
Primary	Levels of subjective sensation related to Hyperventilation Syndrome	The Nijmegen Questionnaire is a clinically used tool for analysis of 16 symptoms related to Hyperventilation syndrome arising from different body systems (such as chest pain, blurred vision and faster or deeper breathing). The participant will choose the answer from a 5-point ordinal scale considering the frequency of symptoms. 23 of 64 points or more is considered positive for abnormality of subjective sensations (van Dixhoorn and Folgering 2015) and correlates positively with Dysfunctional Breathing (Vansteenkiste, Rochette, Demedt, 1991).	This scale will be applied only once and takes about 5 minutes to be completed by the participant.
Primary	Self-evaluation of breathing	The Self Evaluation Breathing Questionnaire is a reliable tool developed by Courtney and Greenwood (2009) to assess breathing pattern of participants with Dysfunctional Breathing (Mitchell et al. 2015). It contains 17 items that are answered using a 4-point Likert scale and includes two main factors: "lack of air", which is about feeling and sensing; and "perception of inappropriate or restricted breathing", which is about observing or noticing. It has been indicated that the higher the SEBQ score, the more severe is the clinical condition of Dysfunctional Breathing (Mitchell et al. 2015). However, researchers who created the SEBQ questionnaire suggested that it can be used as a screening tool for identifying Dysfunctional Breathing and for monitoring changes in breathing symptoms after treatment, but there is no normal value available in the literature for this questionnaire yet (Courtney, Greenwood, et al. 2011).	This scale will be applied only once and takes about 5 minutes to be completed by the participant..
Primary	Respiratory Motion	The Manual Assessment of Respiratory Motion (MARM) will be used to assess thoracic and diaphragmatic movements during breathing and quantify their contribution as a percentage of the total breathing movement. During this evaluation, the examiner will position their open hands between posterior and lateral lower rib cage (lower four to six ribs) and the thumbs will vertically be positioned about 1 inch from the spine. In this position, it is possible for the examiner to identify lateral and vertical movements during breathing, as well as upper or lower rib cage predominance. The examiner will draw an upper, lower and horizontal lines starting from the centre of a circle, building a pie chart with the degree of expansion (Courtney et al. 2008, Courtney and van Dixhoorn 2014). A perfect balance between thoracic and abdominal motion during breathing presents a MARM between 0 and 6; as well as a value above 30 may be considered as dysfunctional (Courtney et al. 2011; Courtney et al. 2008).	This assessment will be applied only once and takes about 10 minutes to be completed.
Primary	Breath-holding time	In the Breath-hold test, the variable considered is the total time the participant is able to hold a breath after a normal exhalation at functional residual capacity. This standardized protocol used in participants with DB is called the Buteyko Method of the Control Pause, where the breath is held and timed until the first involuntary motion of the respiratory muscles (Courtney and Cohen 2008). The breath-holding time has been estimated to be approximately 20 seconds patients with DB, while in healthy people is approximately 60 seconds (Jack et al. 2004, Courtney and Cohen 2008). Three attempts will be undertaken with 5-minute rest in between; a stopwatch will be used to time each one, as well as the intervals. The mean of the three attempts will be analysed, in order to remove any learnt effect (Courtney, Greenwood, et al. 2011).	This assessment will be applied only once and takes about 20 minutes to be completed.
Secondary	Medical History	Participants will be asked about their medical history, health conditions, comorbidities, medicines in use and its doses.	This assessment will be applied during the 3-hour assessment, and takes about 5 minutes to be completed.
Secondary	Age	The date of birth (age) of the participants will be recorded and used for analyses.	This assessment will be applied during the 3-hour assessment, and takes about 20 seconds to be completed.
Secondary	Gender	The gender of the participants will be recorded and used for analyses.	This assessment will be applied during the 3-hour assessment, and takes about 10 seconds to be completed.
Secondary	Weight	The weight of the participants will be recorded based on self-report.	This assessment will be applied during the 3-hour assessment, and takes about 10 seconds to be completed.
Secondary	Height	The height of the participants will be recorded based on self-report.	This assessment will be applied during the 3-hour assessment, and takes about 10 seconds to be completed.
Secondary	Body mass index (BMI)	The body mass index of the participants will be calculated as follows: weight over height squared.	The BMI will be calculated based on height and weight collected from the participants, and will take about 1 minute to be calculated.
Secondary	Level of physical activity	The level of physical activity of the participants will be recorded based on self-report. They will be asked how many days of a typical week they participate in moderate-to-vigorous physical activity. Also, they will be asked how many minutes per day, during a typical week, they participate in moderate-to-vigorous physical activity. Finally, participants will be asked about any sports that they have participated in and at what level.	This assessment will be applied during the 3-hour assessment, and takes about 3 minutes to be completed.
Secondary	Forced vital capacity (FVC)	Lung function will be assessed by spirometry, as hypocapnia is associated with bronchoconstriction (Combes and Fauvage 1997, Brijker et al. 2001). Forced vital capacity (FVC) will be assessed following international recommendations (Miller et al. 2005) and the reference values will be calculated according to Quanjer et al. (1993) and Stanojevic et al. (2010). The participant will be instructed to exhale the maximum possible until residual volume and to inspire as rapid as possible, aiming a maximal and quick gasp until at least 50% of vital capacity.	This assessment will be applied during the 3-hour assessment, and takes about 10 minutes to be completed.
Secondary	Forced expiratory volume in the first second (FEV1)	Lung function will be assessed by spirometry, as hypocapnia is associated with bronchoconstriction (Combes and Fauvage 1997, Brijker et al. 2001). Forced expiratory volume in the first second (FEV1) will be assessed following international recommendations (Miller et al. 2005) and the reference values will be calculated according to Quanjer et al. (1993) and Stanojevic et al. (2010). The participant will be instructed to exhale the maximum possible until residual volume and to inspire as rapid as possible, aiming a maximal and quick gasp until at least 50% of vital capacity.	This assessment will be applied during the 3-hour assessment, and takes about 10 minutes to be completed.
Secondary	Maximum voluntary ventilation (MVV)	Lung function will be assessed by spirometry, as hypocapnia is associated with bronchoconstriction (Combes and Fauvage 1997, Brijker et al. 2001). Forced expiratory volume in the first second (FEV1) will be assessed following international recommendations (Miller et al. 2005) and the reference values will be calculated according to Quanjer et al. (1993) and Stanojevic et al. (2010). The participant will be instructed to ventilate with her or his maximal ventilation volume and frequency, inhaling and exhaling as deep and quick as possible.	This assessment will be applied during the 3-hour assessment, and takes about 10 minutes to be completed.
Secondary	Peak inspiratory flow rate	The peak inspiratory flow rate will be measured based on the protocol described by McConnell (McConnell 2013). The participant will be instructed to exhale the maximum possible until residual volume and to inspire as rapid as possible, aiming a maximal and quick gasp until at least 50% of vital capacity.	This assessment will be applied during the 3-hour assessment, and takes about 10 minutes to be completed (together with the FVC, since this outcome is provided by the same manoeuvre).
Secondary	Peak expiratory flow rate	The peak expiratory flow rate will be measured based on the protocol described by McConnell (McConnell 2013). The participant will be instructed to inhale the maximum possible until total vital capacity and to expire as rapid as possible, aiming a maximal and quick manoeuvre.	This assessment will be applied during the 3-hour assessment, and takes about 10 minutes to be completed.
Secondary	Inspiratory muscle function	Inspiratory muscle strength will be assessed by the maximal inspiratory pressure (MIP) measurement (McConnell and Copestake 1999, Volianitis et al. 2001) using a mouth pressure meter (Micro Medical RPM, Carefusion, San Diego, United States). The protocol to assess inspiratory muscle strength will be the one described by Black and Hyatt (1969), in which MIP is measured starting at residual volume (McConnell 2013). During the manoeuvre the participants will be instructed to sustain a maximal effort for at least 1.5-2.0 seconds, and a minimum of 5 satisfactory efforts will be considered according to Volianitis et al. (2001).	This assessment will be applied during the 3-hour assessment, and takes about 30 minutes to be completed.
Secondary	Expiratory muscle function	Expiratory muscle strength will be assessed by the maximal expiratory pressure (MEP) measurement (McConnell and Copestake 1999, Volianitis et al. 2001) using a mouth pressure meter (Micro Medical RPM, Carefusion, San Diego, United States). The protocol to assess expiratory muscle strength will be the one described by Black and Hyatt (1969), in which MEP is measured starting at total lung capacity (McConnell 2013). During the manoeuvre the participants will be instructed to sustain a maximal effort for at least 1.5-2.0 seconds, and a minimum of 5 satisfactory efforts will be considered according to Volianitis et al. (2001).	This assessment will be applied during the 3-hour assessment, and takes about 30 minutes to be completed.
Secondary	Exercise capacity	The Astrand-Ryhming submaximal test (Astrand and Ryhming 1954) will be used to assess exercise capacity of all participants and to predict maximal oxygen uptake. Participants will be instructed to stay 48 hours previous to the test without practicing exercise. This test will be performed on a cycle ergometer and power outputs of 75 to 150 watts and 100 to 200 watts will be used for women and men, respectively. The rotation of 50 rpm needs to be kept for 6 minutes. The HR is registered at the 5th and 6th minutes of the exercise test, and with the right load, these values cannot differentiate from each other more than 5 bpm. After that, a mathematic model will be used to predict the maximal oxygen uptake (Astrand and Ryhming 1954, Legge and Banister 1986, Macsween 2001).	This assessment will be applied during the 3-hour assessment, and takes about 16 minutes to be completed (simultaneously with the levels of heart rate variability, arterial blood pressure and gas exchange).
Secondary	Level of heart rate variability	The heart rate variability (HRV) will be continuously assessed during five minutes before, during, and five minutes after the exercise test and during a controlled breathing of approximately 6-10 breaths per minute. HRV will be assessed by using a Polar® V800 device (Polar, Kempele-Finland), and the heart's electrical signal will be processed by using Kubios HRV version 2.2. The data will be initially filtered and smoothed to obtain heart rate frequency mean, time-domain analyses of the R-R intervals (interval between 2 "R" curves in the electrocardiogram (e.g., standard deviation of normal-to-normal RR intervals [SDNN] and root mean square of successive differences [RMSSD]) and spectral analyses of frequency indices (i.e., very low-frequency [0-0.04], low-frequency [0.04-0.15 Hz] and high-frequency [0.15-0.4 Hz]) aiming the further understanding of the autonomic nervous system responses in DB.	This assessment will be applied during the 3-hour assessment, and takes about 15 minutes to be placed and will be continuously used during the exercise test (16 minutes) and the slow-breathing task (15 minutes).
Secondary	Level of arterial blood pressure	The arterial blood pressure (ABP) will be continuously assessed during five minutes before, during, and five minutes after the exercise test and during a controlled breathing of approximately 6-10 breaths per minute. Finger ABP will be measured by the use of Finometer 1.10 (Finapres Medical System, Amsterdam - The Netherlands), which non-invasively registers continuous blood pressure measurements. The finger pressure generates a waveform and the ABP is exported based on calculations built every heartbeat (Bogert and van Lieshout 2005). Finger ABP signals will be processed by using the Lab Chart Pro Software, which records, displays and analyses real time data from up to 32 channels.	This assessment will be applied during the 3-hour assessment, and takes about 15 minutes to be placed and will be continuously used during the exercise test (16 minutes) and the slow-breathing task (15 minutes).
Secondary	Minute volume	The indirect calorimetry (IC) will be performed by the portable system K5® (Cosmed, Rome, Italy). This ergospirometer calculates breath-by-breath oscillations of minute volume (VE). The device will be attached to the participant's chest and a facemask, which has less than 30 ml of dead space, suitably adjusted to eliminate air leakage. The equipment will be programmed to assess data breath-by-breath and an average will be recorded every 5 seconds. Oxycon Pro software will be used to process the data for further analyses.	This assessment will be applied during the 3-hour assessment, and takes about 15 minutes to be placed and will be continuously used during the exercise test (16 minutes) and the slow-breathing task (15 minutes).
Secondary	Oxygen Uptake	The indirect calorimetry (IC) will be performed by the portable system K5® (Cosmed, Rome, Italy). This ergospirometer calculates breath-by-breath oscillations of oxygen uptake (O2). The device will be attached to the participant's chest and a facemask, which has less than 30 ml of dead space, suitably adjusted to eliminate air leakage. The equipment will be programmed to assess data breath-by-breath and an average will be recorded every 5 seconds. Oxycon Pro software will be used to process the data for further analyses.	This assessment will be applied during the 3-hour assessment, and takes about 15 minutes to be placed and will be continuously used during the exercise test (16 minutes) and the slow-breathing task (15 minutes).
Secondary	Carbon dioxide	The indirect calorimetry (IC) will be performed by the portable system K5® (Cosmed, Rome, Italy). This ergospirometer calculates breath-by-breath oscillations of carbon dioxide (CO2). The device will be attached to the participant's chest and a facemask, which has less than 30 ml of dead space, suitably adjusted to eliminate air leakage. The equipment will be programmed to assess data breath-by-breath and an average will be recorded every 5 seconds. Oxycon Pro software will be used to process the data for further analyses.	This assessment will be applied during the 3-hour assessment, and takes about 15 minutes to be placed and will be continuously used during the exercise test (16 minutes) and the slow-breathing task (15 minutes).
Secondary	Respiratory exchange ratio	The indirect calorimetry (IC) will be performed by the portable system K5® (Cosmed, Rome, Italy). This ergospirometer calculates breath-by-breath oscillations of respiratory exchange ratio (RER). The device will be attached to the participant's chest and a facemask, which has less than 30 ml of dead space, suitably adjusted to eliminate air leakage. The equipment will be programmed to assess data breath-by-breath and an average will be recorded every 5 seconds. Oxycon Pro software will be used to process the data for further analyses.	This assessment will be applied during the 3-hour assessment, and takes about 15 minutes to be placed and will be continuously used during the exercise test (16 minutes) and the slow-breathing task (15 minutes).
Secondary	Respiratory rate	The indirect calorimetry (IC) will be performed by the portable system K5® (Cosmed, Rome, Italy). This ergospirometer calculates breath-by-breath oscillations of respiratory rate (breaths per minute - BPM). The device will be attached to the participant's chest and a facemask, which has less than 30 ml of dead space, suitably adjusted to eliminate air leakage. The equipment will be programmed to assess data breath-by-breath and an average will be recorded every 5 seconds. Oxycon Pro software will be used to process the data for further analyses.	This assessment will be applied during the 3-hour assessment, and takes about 15 minutes to be placed and will be continuously used during the exercise test (16 minutes) and the slow-breathing task (15 minutes).
Secondary	Attentional focus	Attentional focus (Attention Scale [AS]; Tammen 1996, Tenenbaum et al. 2007) will be measured at various time points (pre exercise, at the 3rd minute, and at the end of the exercise test) during the execution of the six-minute cycling test described above.	This assessment will be applied 3 times during the exercise test, and takes about 30 seconds to be completed each time. So, it will take approximately 1 minute and 30 seconds to be applied in total.
Secondary	Level of fatigue	Limb discomfort (Category Ratio 10 [CR10-fatigue]; Borg 1982) (Borg Scale fatigue) will be measured at various time points (pre exercise, at the 3rd minute, and at the end of the exercise test) during the execution of the six-minute cycling test described above.	This assessment will be applied 3 times during the exercise test, and takes about 15 seconds to be completed each time. So, it will take approximately 45 seconds to be applied in total.
Secondary	Level of dyspnoea	Dyspnoea (CR10-dyspnoea; Borg 1982) (Borg Scale dyspnoea) will be measured at various time points (pre exercise, at the 3rd minute, and at the end of the exercise test) during the execution of the six-minute cycling test described above.	This assessment will be applied 3 times during the exercise test, and takes about 15 seconds to be completed each time. So, it will take approximately 45 seconds to be applied in total.