How Many HBOT Sessions Do You Need for Long COVID?

Clinical trials that found positive results for long COVID used 40 to 60 Hyperbaric Oxygen Therapy (HBOT) sessions at 2.0 atmospheres absolute (ATA), delivered five days per week over 8 to 12 weeks. The two trials that used only 10 sessions found no benefit. This dose-response pattern is the single most important variable in HBOT outcomes for long COVID.

What Session Counts Did the Trials Use?

The evidence base for HBOT and long COVID includes 10 randomized controlled trials (RCTs) and 8 systematic reviews as of 2026. The protocols varied, and the results tracked directly with session count.

40-session protocols (positive results). The landmark Tel Aviv RCT by Zilberman-Itskovich et al. (2022) used 40 daily sessions at 2.0 ATA with 100% oxygen, each lasting 90 minutes (including 5-minute air breaks every 20 minutes). This trial found significant improvements in cognitive function, fatigue, sleep, pain, and psychiatric symptoms. Brain MRI confirmed increased cerebral perfusion. The sham control group received room air at 1.0 ATA and showed no improvement, confirming the results were not from placebo effect¹.

60-session protocols (positive results). A detailed case report by Bhaiyat et al. (2022) documented 60 sessions at 2.0 ATA for a 55-year-old man with severe post-COVID symptoms. Results included a 34% increase in VO2max, 44% improvement in forced vital capacity, and significant cognitive gains confirmed by perfusion MRI and diffusion tensor imaging. The additional 20 sessions (beyond the standard 40) appeared to produce further gains in this severely affected patient².

14-session protocol (positive results). A 2026 Vietnamese study (Ha Nguyen Thi Hai et al.) used only 14 sessions at 2.2 ATA (slightly higher pressure than the Tel Aviv trial). Despite the shorter course, quality of life improved from 0.749 to 0.942 on EQ-5D-5L (p<0.001), cerebral blood flow normalized from 37.3% to 78.4% of patients, and antioxidant activity increased significantly. However, this was not sham-controlled, meaning placebo effect cannot be ruled out³.

10-session protocols (null results). Two RCTs published in 2025, referenced in the comprehensive review by Zoccali et al. (2026), used only 10 HBOT sessions. Neither found significant benefit over sham. These are the most important negative studies in the field because they establish a clear floor: 10 sessions is insufficient for long COVID⁴.

The Dose-Response Pattern Is Clear

Across all published long COVID HBOT research, a consistent pattern emerges:

• 40+ sessions: Consistently positive results across multiple outcomes (cognition, fatigue, psychiatric symptoms, pain, quality of life)
• 14-20 sessions: Some improvement in specific measures, but weaker and less consistent. May work for patients with milder symptoms or when used at slightly higher pressures (2.2 ATA)
• 10 sessions: No measurable benefit over sham in controlled trials

This tracks with what the 2025 systematic review by Zamora et al. found across seven studies (199 participants, seven countries): protocols using 100% oxygen at 2.0-2.5 ATA for 40-60 sessions produced the most reliable improvements in memory, executive function, attention, and fatigue⁵.

The dose-response relationship is not unique to long COVID. HBOT research in other conditions (traumatic brain injury, radiation injury, diabetic wounds) shows similar patterns where a minimum number of sessions is required before clinical benefit appears. The biological explanation is that angiogenesis (new blood vessel formation) and neuroplasticity (new neural connections) are cumulative processes that require repeated stimulus over weeks, not days.

What Does the HBOT Protocol Look Like?

Based on the positive trial data, the standard HBOT protocol for long COVID looks like this:

• Pressure: 2.0 ATA (some studies used up to 2.5 ATA)
• Oxygen: 100% medical-grade oxygen via hard chamber
• Session duration: 90 minutes total (including 5-minute air breaks every 20 minutes, where the patient breathes room air briefly before resuming 100% oxygen)
• Frequency: 5 sessions per week (Monday through Friday)
• Total sessions: 40 (minimum based on strongest evidence)
• Timeline: 8 weeks at 5 sessions/week

Some clinics extend to 60 sessions over 12 weeks, particularly for patients with severe cognitive impairment or multiple long COVID symptom clusters. The air breaks during each session are intentional. The intermittent return to normoxia (normal oxygen levels) triggers a cellular response similar to interval training. Cells “sense” the contrast between hyperoxia and normoxia, activating repair and growth pathways more effectively than continuous oxygen exposure alone.

When Do You Start Feeling Better?

Published data and clinical reports suggest a typical improvement timeline, though individual responses vary.

Weeks 1-2 (sessions 1-10): Most patients report no cognitive or fatigue improvement. Some notice better sleep or reduced headache frequency. Energy may fluctuate, with some patients feeling more tired in the first week as the body adjusts to repeated hyperoxygenation. Minor ear pressure discomfort during the first few sessions is common and usually resolves as patients learn equalization techniques. The null results from 10-session trials confirm that stopping here is too early to evaluate whether HBOT will work.

Weeks 3-4 (sessions 11-20): Subtle shifts in mental clarity for some patients. Word recall may improve slightly. Some patients report that brain fog episodes become shorter, lasting hours instead of entire days. Reading stamina may increase from 5-10 minutes to 20-30 minutes. The Vietnamese 14-session study found quality-of-life improvements in this window, suggesting some physiological changes are underway even before full protocol completion.

Weeks 5-6 (sessions 21-30): More noticeable cognitive improvement for responding patients. Ability to follow multi-step conversations, plan daily activities, and manage cognitive tasks improves. Some patients begin returning to light work or resuming hobbies they had given up. This is the phase where many patients begin to feel confident the treatment is working.

Weeks 7-8 (sessions 31-40): The Tel Aviv trial found the strongest gains across the full 40-session course. Attention, processing speed, and executive function improvements consolidate. Brain MRI changes are most apparent at this point. Patients commonly report a qualitative shift in their cognitive capacity, describing it as “the fog lifting” or “being able to think clearly again for the first time in months.”

After completion: The one-year follow-up by Catalogna et al. (2024) found that cognitive improvements persisted at 12 months, suggesting the brain changes (new blood vessels, new neural connections) are permanent structural changes rather than temporary effects of oxygenation⁶.

Factors That Affect How Many Sessions You Need

The 40-session standard is a starting point, not a fixed rule. Several factors may require adjustment.

Symptom severity. Patients with severe cognitive impairment or multiple symptom clusters (fatigue plus brain fog plus pain plus psychiatric symptoms) may benefit from extending to 60 sessions. The Bhaiyat case report used 60 sessions and achieved dramatic improvements in a severely affected patient. More damaged tissue requires more exposure to the growth signals that HBOT provides.

Time since infection. Most trial participants were 3-18 months post-infection. Whether patients who are 2+ years into long COVID need more sessions is not well-studied, though registry data from van Berkel et al. (2025) included patients at various time points and still found 56-63% improvement rates. Longer disease duration may mean more entrenched pathology that takes longer to reverse, but this is speculative⁷.

Comorbidities. Patients with pre-existing conditions (autoimmune disease, diabetes, prior neurological conditions) may respond differently. The registry data noted that not all patients improve, with 13-19% experiencing worsening symptoms. Pre-existing conditions may compete with long COVID pathology for the body’s repair resources.

Protocol adherence. Missing sessions disrupts the cumulative oxygenation effect. Five sessions per week appears important because it maintains consistent stimulus for angiogenesis and neuroplasticity. Reducing to 2-3 sessions per week may require more total sessions to achieve the same result, though no trial has directly tested this. If work or travel forces you to miss sessions, try to make them up rather than simply extending the gaps.

Pressure level. Most trials used 2.0 ATA. The Vietnamese study used 2.2 ATA and found benefits with fewer sessions (14 vs 40), suggesting higher pressure may compensate partially for fewer sessions. However, higher pressure increases the risk of side effects (ear barotrauma, transient vision changes), and the relationship between pressure and session count is not well enough understood to make specific recommendations.

What About Maintenance Sessions After the Initial Course?

No published trial has specifically studied maintenance HBOT protocols for long COVID. Here is what the available data suggests.

The one-year follow-up data from Catalogna et al. shows that the benefits of a full 40-session course are durable. Cognitive improvements persisted at 12 months without any additional HBOT sessions during that year. This means maintenance sessions may not be necessary for patients who complete the full protocol and achieve satisfactory improvement.

Some clinics offer monthly or quarterly “booster” sessions. This practice is based on clinical experience rather than trial data. There is no published evidence that booster sessions provide additional benefit beyond the initial course. Patients who are offered boosters should understand this is a clinical judgment call, not an evidence-based recommendation.

For patients who improve but do not fully resolve, a second 40-session course may be considered after a break period. The rationale is that additional neuroplasticity and angiogenesis stimulus could drive further improvement. This approach has not been studied in RCTs for long COVID specifically, but the concept has precedent in HBOT for other neurological conditions.

For patients interested in home-based maintenance, soft chambers (1.3 ATA) are sometimes used as a maintenance tool after completing a clinical hard chamber protocol. This is not a substitute for the clinical protocol and has no direct evidence supporting it. See our article on chamber costs for pricing.

What This Means for Your Budget

Session count directly drives cost. At typical clinic pricing of $150-400 per session:

• 40 sessions at $150/session: $6,000
• 40 sessions at $250/session: $10,000
• 40 sessions at $400/session: $16,000
• 60 sessions at $250/session: $15,000
• 60 sessions at $400/session: $24,000

Package deals and memberships can reduce per-session cost by 15-40%, bringing a 40-session course closer to $4,000-$10,000 at some clinics. Multi-session packages of 20-40 sessions typically offer the best per-session rate. Always ask for the package price before committing to single-session pricing.

Long COVID is not currently covered by insurance, meaning every dollar comes out of pocket. HSA and FSA accounts can typically be used for HBOT at a licensed medical facility, effectively reducing cost by your tax rate (22-37%). See our full guide on HBOT cost and insurance for long COVID for detailed financial strategies.

Seph Fontane Pennock

Author

Seph Fontane Pennock is the founder of BaricBoost.com and Regenerated.com, a clinic directory for regenerative medicine serving 10,000+ providers across the United States. He previously built and sold PositivePsychology.com, which grew to 19 million users and became the largest evidence-based positive psychology resource on the web. Seph brings direct experience as an HBOT patient, having completed protocols at clinics across three continents while navigating mold illness, systemic inflammation, and autoimmune conditions. His treatment journey includes hyperbaric oxygen therapy, peptide protocols, NAD+ therapy, and consultations with specialists from Dubai to Cape Town to Mexico. This combination of entrepreneurial track record and lived patient experience shapes everything published on BaricBoost.com. Every article is grounded in peer-reviewed research, informed by real clinical encounters, and written for patients making high-stakes treatment decisions. Seph's focus is on bringing transparency, scientific rigor, and practical guidance to the hyperbaric oxygen therapy space.

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