Non-invasive investigation of the cardiodynamic response to breathing exercises in healthy individuals using impedance cardiography: a feasibility study v1

Respiratory exercises are widely prescribed in physiotherapy to improve lung volumes, facilitate airway clearance, and enhance respiratory muscle performance. Techniques such as, diaphragmatic breathing, slow deep breathing, huffing and positive expiratory pressure (PEP) aim to reduce dyspnoea, prevent atelectasis, and support secretion mobilisation, particularly in postoperative and bed-bound patients. Beyond their pulmonary benefits, respiratory exercises can impose a systemic physiological load. By increasing metabolic demand and altering intrathoracic pressure, they influence venous return, preload, and stroke volume, thereby affecting hemodynamic parameters such as heart rate (HR), cardiac output (CO), and cardiac index (CI). These acute hemodynamic effects are particularly relevant in frail, elderly, or acutely unwell populations,including patients with pre-existing cardiorespiratory conditions; however, they remain poorly characterised. This project aims to investigate the feasibility, safety and acceptability of implementing a study protocol with measurement of acute changes in hemodynamic variables, including heart rate (HR), stroke volume (SV), cardiac output (CO), and cardiac index (CI) in response to controlled incremental respiratory exercises protocol using impedance cardiography (ICG). It will also provide preliminary effect estimates, identify potential measurement challenges, and refine procedural elements, such as respiratory exercise progression, timing of data collection, and symptom monitoring for future clinical trial. Healthy adult participants will complete incremental respiratory exercise sessions, with measurements taken at baseline, during the intervention, and throughout the recovery period. Symptom assessment will accompany physiological monitoring to explore its relationship with hemodynamic responses.