NIRS analysis of periodic breathing in heart failure: unraveling ventilation-perfusion dynamics

Background Periodic breathing (PB) during exercise refers to a gradual. noticeable. and cyclic fluctuation in minute ventilation oxygen uptake (V̇O2) and carbon dioxide elimination (V̇CO2). This pattern may endure throughout the entire exercise session or be apparent only in the initial phases. Its presence is linked to an unfavorable prognosis in patients with heart failure (HF). particularly when concurrent with periodic breathing during sleep. It is unknown whether PB influences O2 availability in the muscles. Near infra-red spectroscopy (NIRS) allows to monitor changes in total. oxygenated and deoxygenated haemoglobin concentration and it has been used in heart failure (HF). to assess muscle oxygenation status. Methods We enrolled HF patients who had been found with PB during HF hospitalization or ambulatory cardiopulmonary exercise test (CPET). NIRS was performed within 1-2 days after clinical observation PB. We measured at rest. continuously and simultaneously. ventilation. ventilatory gas exchange. heart rate. O2 saturation. total and oxygenated/deoxygenated hemoglobin content over the quadriceps by NIRS. Respiratory data were collected by spirometer, while hemoglobin muscle data by NIRS and then data were integrated. Results We enrolled 20 patients (70±10 years. 95% males. LVEF 27±8%). Baseline data and results obtained at maximal CPET are shown in table 1. Five patients did not show PB during the NIRS measurement period. In all cases where oscillatory behaviour of respiratory gases could be observed (n=15). an oscillation of oxygenated (HbO2) and deoxygenated hemoglobin (HHbO2) in the muscle was also found. We observed two different behaviours of NIRS traces. In most cases HbO2 had an oscillation exactly counterphase to the oscillation of HHbO2 (Figure 1. left). In contrast. one case showed a concordant oscillation of the two traces (figure 1. right). In this case total Hb was almost constant). By analysing the concordance between the ventilation and respiratory gas oscillation in all cases. an exact correspondence of the number of respiratory oscillations to those detected at the muscle could be found. Conclusions Our study revealed two distinct patterns of NIRS. Those with an oscillation in oxygenated (HbO2) and deoxygenated hemoglobin (HHbO2) with a counterphase relationship. suggest a potential oscillation in ventilation/perfusion mismatch. In contrast. the concordant oscillations in both traces. accompanied by evident pulsatility in total hemoglobin. may be indicative of a possible cardiac output-related periodicity. Further research is warranted to elucidate the specific mechanisms driving these distinct patterns and their clinical implications in the context of heart failure. Understanding the underlying causes of periodic breathing may contribute valuable insights for tailored interventions and improved prognostic assessment in HF patients.