Introduction/Aim: Heart failure (HF) is a complex clinical syndrome, characterised by reduced exercise capacity (VO 2 peak) and quality of life leading to premature death. The reduction in VO 2 peak is a key prognostic indicator, and improving exercise capacity remains a critical therapeutic target. In athletes, the use of intermittent hypoxia training to improve VO 2 peak and performance is well established. Changes in VO 2 peak are typically accompanied by improved oxygen carrying capacity with increased haemoglobin (Hb) concentration mediated through increased erythropoietin (EPO) production in the kidney. The purpose of this pilot study was to examine the feasibility of using intermittent hypoxia training in individuals with HF, and examine changes in VO 2 peak, EPO and Hb. We hypothesised that intermittent hypoxia training would be feasible, well tolerated, and improve VO 2 peak, EPO production, Hb concentration in HF with reduced ejection fraction (HFrEF). Methods: Ten male participants with stable, optimally managed HFrEF (Age: 73 ± 5 yr; Ejection Fraction: 37 ± 11%) participated in the study. The training stimulus consisted of 12 x 60-minute sessions of intermittent hypoxia over a 2-week period. During each 60-minute session participants received 6 x 5 minutes of pulsed, reduced FIO 2 exposures interspersed with 5 min of normoxia (total of 30 min hypoxic exposure per session). All participants commenced at 18% FIO 2 , which was decreased to 12% by the 3-4th sesion, as tolerated. Throughout each exposure, oxygen saturation (SpO 2 ), heart rate, blood pressure and dyspnoea (modified Borg scale) were monitored every 5 min. Changes in VO 2 peak were measured using a cycle ergometry, cardiopulmonary exercise test. Changes in VO 2 peak, N-terminal pro B-type natriuretic peptide (NT-proBNP), EPO and Hb concentration were measured pre and immediately post intermittent hypoxic training. Results: All participants completed between 10-12 (median n=12) sessions over the 2-week period. Intermittent hypoxia was well-tolerated with no adverse events. The mean SpO 2 during the hypoxic exposure was 88 ± 4%, and median reported dyspnoea 0 (range 0-1). Following 2 weeks of intermittent hypoxic training, there were significant increases in VO 2 peak (mean differenceMD: +1.18 mL·kg - ¹·min - ¹, 95% CI 0.47 to 1.89, p = 0.010); EPO (MD: +3.33 IU/L, 95% CI 1.35 to 5.32, p = 0.011); with a modest increase in Hb concentration that approached significance (MD: +4.00 g/L, 95% CI 0.51 to 7.49, p = 0.055). NT-proBNP remained unchanged (MD: –107 pg/mL, 95% CI –356 to 142, p = 0.424). Conclusion The results of this pilot study suggest that in clinically stable HFrEF, 2 weeks of intermittent hypoxic training results in a significant improvement in VO 2 peak, accompanied by increases in EPO and potentially levels of Hb. In our participants, this 60-minute pulsed intermittent hypoxic protocol was extremely well tolerated without any adverse effects, and may improve oxygen carrying capacity of the blood in HFrEF. Further research on the mechanisms of adaptation and the translation of the response into different HF phenotypes is warranted. Supported By: The Prince Charles Hospital Foundation Innovation Grant INN202-049 and Griffith University. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Morris et al. (2026) studied this question.