Intermittent Hypoxic-Hyperoxic treatment (IHHT)

What is intermittent hypoxic-hyperoxic training?

Intermittent hypoxic-hyperoxic training (IHHT) alternates between breathing low-oxygen (hypoxic) and high-oxygen (hyperoxic) air through a specialized mask. A typical session lasts 30-45 minutes, cycling between 3-5 minutes of hypoxia (10-15% oxygen, simulating 2,500-3,500 meters altitude) and 3-5 minutes of hyperoxia (30-40% oxygen). This controlled stress-recovery pattern triggers adaptive responses throughout the body ^[1].

How IHHT works

The hypoxic phases activate hypoxia-inducible factor (HIF), a protein that switches on genes responsible for oxygen transport and cellular energy production. This increases erythropoietin (EPO) release, stimulates new blood vessel formation (angiogenesis), and promotes mitochondrial biogenesis. The hyperoxic phases that follow flood tissues with oxygen, allowing cells to utilize these newly built systems more efficiently ^[2].

Evidence-based benefits

Long COVID recovery

A 2024 controlled trial with 145 long COVID patients found that IHHT added to standard rehabilitation improved walking distance 2.8-fold compared to rehabilitation alone. Participants also showed greater improvements in stair climbing, reduced breathlessness, less fatigue, and better quality of life. Blood pressure and heart rate decreased significantly in the IHHT group ^[1].

Cognitive function in older adults

Research on geriatric patients (ages 64-92) demonstrated that IHHT combined with multimodal training improved cognitive test scores by 16.7% versus no improvement in the control group. Walking distance improved 24.1% compared to 10.8% in controls. The treatment was well tolerated even in patients up to 92 years old ^[3].

Metabolic health

A randomized trial in patients with metabolic syndrome showed that three weeks of IHHT reduced systolic blood pressure by a large effect size (Cohen's d = 1.15) and diastolic pressure by a moderate effect (d = 0.7). Participants also saw reductions in total cholesterol, LDL cholesterol, and liver fat content compared to controls ^[4].

Cardiovascular protection

In patients undergoing coronary artery bypass surgery, preoperative IHHT reduced markers of heart muscle damage. Troponin I levels 24 hours after surgery were significantly lower in the IHHT group compared to both standard care and remote ischemic preconditioning groups ^[5].

Safety and practical considerations

IHHT has demonstrated an excellent safety profile across multiple studies. No serious adverse events were reported in clinical trials involving elderly patients, cardiac patients, or those with metabolic syndrome. However, IHHT should be administered under medical supervision, particularly for individuals with cardiovascular conditions. The therapy is best viewed as a complement to, not a replacement for, regular exercise and established medical treatments.