Peripheral oxygenation in heart failure patients with periodic breathing: insights from NIRS

Aims Periodic breathing (PB) is characterized by cyclic fluctuations in ventilation and expired gases. PB is observed at rest or during exercise and is a marker of poor prognosis. In this study, we investigated whether PB affects oxygen availability in peripheral muscles.Materials and results This pilot, prospective, single-centre study enrolled severe reduced ejection fraction heart failure (HF) patients exhibiting PB. Oxygenated (O2Hb) and deoxygenated haemoglobin (HHb) in the quadriceps femoralis were measured using near-infrared spectroscopy (NIRS), along with ventilation and expired gases. NIRS and ventilation data were collected at rest and analysed for cyclic patterns. Clinical evaluations, including the cardiopulmonary exercise test (CPET) and echocardiography, were performed. The Metabolic Exercise Combined with Cardiac Kidney Indexes (MECKI) score was used for prognosis evaluation. Twenty HF patients with PB were evaluated. NIRS revealed two distinct periodic behaviours: in 7 patients, O2Hb and HHb fluctuated in-phase; in 13, they were out-of-phase. In-phase patients had higher left ventricular ejection fraction, lower LV volumes, and lower BNP and soluble interleukin 1 receptor family member ST2 concentrations. Out-of-phase patients had more severe HF, with longer, less variable cycles and a higher MECKI score. Six of 13 out-of-phase patients died within 6 months, compared with 2 of 7 in-phase patients.Conclusion PB is associated with distinct peripheral oxygenation patterns, potentially representing disease progression stages. In-phase O2Hb and HHb suggest blood flow cycling, while out-of-phase behaviour suggests periodicity in ventilation/perfusion mismatching. These findings provide novel insights into the dynamic effects of PB on peripheral oxygenation.