The overall aim with the proposed research project is to describe and investigate the
underlying mechanisms of dysfunctional breathing and the experience of living with
dysfunctional breathing in patients with post-COVID-19 conditions. In addition, validate
and evaluate which methods measure dysfunctional breathing regarding content validity,
conceptual validity, test-retest reliability, and sensitivity to change for patients with
post-COVID-19 conditions. Furthermore, to develop and evaluate an individually adapted
intervention with the aim of normalizing the breathing pattern. In the next step, to
evaluate the effects of an individually adapted intervention on physical and
psychological function and health-related quality of life (HRQoL) in patients with
post-COVID-19 conditions, as well as to describe the patients' experiences of
rehabilitation.

Methods and planned studies This project is a part of a larger multi-disciplinary and
multi-professional study, ReCOV, that takes a holistic perspective on the consequences of
the disease. ReCOV is a three-armed project including patients, next of kin and staff
(23). Patients have been followed up at the out-patient clinic for patients with PCC at
Karolinska University Hospital (K).

The longitudinal observational study is about physical and psychological recovery,
objectively measured physical activity and also an interview study of the patients'
overall experiences of rehabilitation after COVID-19 both in the acute and long-term
perspective. In total approximately 950 patients have accepted to be apart of ReCOV and
to this proposed project patients will be recruited from this cohort but also from
primary care. This research project will be performed in collaboration with Karolinska
Institutet, Karolinska university Hospital (K), Sahlgrenska University Hospital (SH).
University of Gothenburg and primary care in Region Stockholm.

Study 1: Dysfunctional breathing in patients with post COVID-19 condition?

Aim: To investigate what signs, symptoms and assessment which can describe and explain
dysfunctional breathing in patients with post COVID-19 condition.

Design: Cross-sectional design

Participants: Patients (approximately n=200) for this study will be recruited from the
ReCov cohort. All patients will be > 18 years old. Patients that state that they have
persistent respiratory problems and abnormal clinical respiratory findings will be
included. Patients will also be recruited from primary care if they have suspected
dysfunctional breathing pattern (unable to breathe with a normal breathing pattern in
standing). Exclusion Criteria: Not able to perform the measurements because of cognitive
or physical impairments, ongoing intervention of breathing exercises.

Procedure and outcomes: All included patients will be evaluated for physical and
psychological function, symptoms and HrQoL. The following measurements and questionnaires
will be used:

Dependent variables (primary outcome):

Health-related Quality of Life (EQ-5D-5L), EQ VAS Breathing pattern by Respiratory
Movement Measuring Instrument (RMMI)

Independent, confounding and possible moderating variables:

Inspiratory and expiratory muscle strength (MIP and MEP) (Micro-RPM) Chest mobility by
thoracic expansion Six-minute walk to measure endurance (in meters) Spirometry
Diaphragmatic ultrasound End tidal CO2 measured during exercise

Physical Activity level (Frändin/ Grimby) Nijmegen questionnaire (dysfunctional
breathing) COPD Assessment Test (CAT), questionnaire of symptoms related to breathing and
now commonly used for this group of patients Dyspnea (mMRC, Modified Medical Research
Council, Dyspnea Scale and BORG CR10) Patient Health Questionnaire (PHQ-9) Generalized
Anxiety Disorder 7-item scale (GAD-7) Breathing Pattern Assessment Tool (BPAT)