|University of New South Wales
|Graduate School of Biomedical Engineering
|Cardiac failure; Sleep disordered breathing; Heart failure; Sleep apnea; Cheyne-stokes respiration; Pulmonary oedema; Adaptive servoventilation; Polysomnography; Apnealink; Sleepminder; Continuous positive airway pressure
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Timely detection of signs and symptoms of congestion to allow for clinical intervention and prevent patient hospitalisation for cardiac failure has been a challenge. The breathing disorders which can manifest in congestive cardiac failure may provide an avenue for sourcing markers of congestion; however monitoring systems capable of long-term observation of patients are required. Practical, long-term monitoring systems were developed for sleep disordered breathing (SDB) in cardiac failure and for the detection of respiratory changes that may relate to impending decompensation of cardiac failure. A portable sleep monitoring device (ApneaLink, ResMed Ltd.) was evaluated against polysomnography (PSG) to characterise SDB in cardiac failure. In clinically unstable cardiac failure, the AHI of in-patients was found to vary by up to 10 events/hr over 3 sleep studies. Whilst it was challenging for patients to adopt the ApneaLink as a home monitoring tool, the severity of SDB was found to traverse multiple categories for SDB severity in out-patients. PSG was impractical to monitor cardiac failure patients on more than 1 night in-hospital. As an alternative to PSG, a test regimen for assessing Cheyne-Stokes respiration (CSR) in the wake state was developed and evaluated. Whilst the test could not differentiate patients with CSR, further modifications to the test may realise this objective. Respiratory monitoring and SDB treatment devices were investigated for the detection of respiratory changes that may relate to decompensation of cardiac failure. The parameters derived from actigraphy based sleep assessment and positive airway pressure therapy devices were found to be feasible and apparently clinically beneficial surrogate measurement methods for pulmonary fluid status in cardiac failure patients. Decompensation of cardiac failure appeared to increase the probability of CSR by 70 %, increase AHI by 30 events/hr or increase respiratory rate by 25 % in the days or weeks prior to hospitalisation. The results highlight the kinetics of SDB in cardiac failure and the limitations of conventional intermittent review of SDB and cardiac failure. Serial respiratory monitoring may be a mechanism by which patient clinical state can be assessed on an ongoing basis in cardiac failure.