Oxygen desaturation during showering identifies patients at risk of early heart failure deterioration

Background Early post-discharge deterioration represents a vulnerable phase in heart failure (HF) and remains a major unmet clinical challenge. A home-applicable, standardised physiological stress assessment is therefore needed. Showering is a universal daily activity imposing a moderate load (2–3 METs) and frequently provokes dyspnoea in HF patients. Waterproof wearable technology now enables continuous second-by-second oxygen saturation monitoring during real-world activities. Whether continuous SpO₂ monitoring during showering provides a reliable home-based assessment remains unclear. Purpose To evaluate whether oxygen saturation measured during showering is associated with early post-discharge clinical outcomes in patients hospitalised for acute HF. Methods In this prospective observational study, 82 consecutive patients hospitalised for acute HF underwent continuous second-by-second SpO₂ monitoring prior to discharge using a waterproof wearable pulse oximeter. Mean SpO₂ during a single showering session under stable clinical conditions (SpO₂-shw) was calculated for each patient. Patients were followed for 90 days for a composite endpoint of HF rehospitalisation or cardiovascular death. Associations between SpO₂-shw and outcomes were assessed using Cox proportional hazards models, analysed as a continuous variable and by median stratification. Results The mean age was 78.4 years, 48% of patients were female, mean left ventricular ejection fraction (LVEF) was 46.7%, and median NT-proBNP was 2124 pg/mL. SpO₂-shw showed a modest inverse correlation with NT-proBNP (r = −0.252; 95% CI −0.445 to −0.038; p = 0.022). When analysed as a continuous variable, SpO₂-shw was inversely associated with the composite endpoint (HR 0.90 per 1% increase; 95% CI 0.82–0.99; p = 0.036). This association remained significant after adjustment for age (p = 0.043) and LVEF (p = 0.045). The median SpO₂-shw was 92.3%. Patients with SpO₂-shw ≤92.3% experienced significantly higher event rates, with early post-discharge separation of Kaplan–Meier curves. Low SpO₂-shw was associated with an approximately threefold increased risk of the composite endpoint (HR 3.41; 95% CI 1.10–10.58; p = 0.034). Conclusions Reduced oxygen saturation during showering was associated with early HF deterioration. Continuous second-by-second monitoring during a routine daily activity such as showering may provide clinically relevant physiological information without formal exercise testing. This simple home-applicable approach may support early post-discharge risk stratification.