CONGRESS ABSTRACT

Background: Periodic breathing (PB) during exercise involves cyclic fluctuations in minute ventilation, oxygen uptake (V̇O2), and carbon dioxide elimination (V̇CO2). It may persist throughout exercise or only appear initially and is linked to poor prognosis in heart failure (HF) patients, especially when concurrent with sleep-related PB. The effect of PB on muscle oxygen availability is unknown. Near-infrared spectroscopy (NIRS) monitors changes in total, oxygenated, and deoxygenated hemoglobin concentration and has been used to assess muscle oxygenation in HF. Methods: We enrolled HF patients with PB identified during hospitalization or ambulatory cardiopulmonary exercise testing (CPET). NIRS was performed 1-2 days after PB observation, measuring continuously and simultaneously ventilation, gas exchange, heart rate, O2 saturation, and oxygenated/deoxygenated hemoglobin content in the quadriceps. Data from spirometers and NIRS were integrated. Results: Of 28 enrolled patients, 4 were excluded for technical reasons and 4 for absence of PB during NIRS evaluation. The remaining 20 patients were all male, 67±11 years old, with an LVEF of 26±11%. Oscillations in respiratory gases were paralleled by oscillations in oxygenated (HbO2) and deoxygenated hemoglobin (HHbO2). In 13 patients (Figure 1, B), HbO2 oscillated counterphase to HHbO2, while in 7 patients (Figure 1, A), both traces oscillated concordantly, with total Hb almost constant. Table 1 shows differences between in-phase and counter-phase patients. Six of the 13 counterphase patients died within 6 months, averaging 192 days survival, compared to 2 deaths in the concordant group. Conclusions: Two distinct NIRS patterns were identified. Counterphase oscillations of HbO2 and HHbO2 may indicate ventilation/perfusion mismatch, while concordant oscillations might suggest cardiac output-related periodicity. Counterphase patterns were associated with more severe clinical status. Further research is needed to understand the mechanisms and clinical implications of these patterns, potentially improving interventions and prognosis in HF patients.