Author(s): REUVENY, R., ALTMAN, N., ANAF, Y., SHAFRAN, I., JONES, A., WILKERSON, D., EPSTEIN, Y., SEGEL, M., Institution: UNIVERSITY OF HAIFA, Country: ISRAEL, Abstract-ID: 765

INTRODUCTION:
Exercise intolerance is a defining symptom in patients with heart failure (HF).
AIM: To study the effect of O2 supplementation on exercise physiology in patients with heart failure with reduced ejection fraction (HFrEF) and preserved ejection fraction (HFpEF).

METHODS:
8 patients with HFrEF (age 59±18 yrs., 7 males, EF 31±5%, peak V̇O2 67±12 %pred, NYHA 2), 9 patients with HFpEF (age 70±7 yrs., 4 males, EF 58±3%, peak V̇O2 69±14 %pred NYHA = 2) and 13 healthy individuals (age 50±17 yrs., 7 males, peak V̇O2 83±13 %pred) were tested. HF patients performed symptom-limited cardiopulmonary exercise tests and constant work-rate tests (CWRTs) at 80% of the work-rate (WR) at the gas exchange threshold (GET). Tests performed on room air (RA, FiO2 0.21) were compared to tests performed breathing 30% O2 (FiO2 0.30), a clinically applicable level of O2 supplementation. Healthy individuals performed a maximal test only with RA, and a CWRT under both conditions (RA and 30% O2). O2-uptake (V̇O2) kinetics were calculated from the CWRTs results using mono-exponential modelling. Right vastus lateralis muscle oxyhemoglobin tissue saturation index (TSI) was measured by near-infrared spectroscopy (NIRS).
RESULTS:
In the HFrEF group, peak WR and peak V̇O2 improved significantly with 30% O2 compared to RA (mean ± SD 103±35 vs 95±30 W and 18.5±4 vs 17.4±3.3 ml/kg/min, p=0.018 and p=0.036, respectively). The phase II time constant (tau) of V̇O2 kinetics in CWRTs was faster in HFrEF patients while breathing with 30% O2 (48±13 sec) compared to RA (55±15 sec, p=0.043). The O2 deficit in the CWRTs was lower while breathing with 30% O2 (0.61±0.16 L) compared to RA (0.78±0.16 L, p=0.046). There was no difference in TSI (%change between rest to peak exercise) between RA and 30% O2 (18±9 vs 16±6%). In the HFpEF group, there were no differences between RA and 30% O2 in peak WR, peak V̇O2 or V̇O2 kinetics. There was no difference between RA and 30% O2 in V̇O2 kinetics in healthy individuals (tau 35±6 sec vs 35±6 sec, p>0.05).
CONCLUSION:
A clinically applicable level of O2 supplementation (30% O2) improved peak exercise capacity and oxygen-uptake kinetics in patients with HFrEF, apparently by increasing central adaptation. No improvement was seen in HFpEF with 30% O2. The utility of O2 supplementation in exercise training of HFrEF patients should be studied further.