Post-COVID-19 syndrome is an assembly of symptoms, following an infection with Coronavirus disease 2019 (COVID-19). The syndrome is characterized by cognitive impairment, fatigue, sleep disorders, smell and taste disorders, pain and more. This long-term sequela can last for months after recovering from the virus, and no treatment is known to date. The aim of this study is to compare the effect of HBOT vs. Sham on post COVID-19 syndrome

Post-COVID-19 syndrome is an assembly of signs and symptoms first described on patients recovering from severe Coronavirus 2019 (COVID-19) infection. The syndrome is characterized by cognitive impairment, fatigue, and other neurologic symptoms. With time, and the growing understanding on this unique virus, there is cumulative case series reports on patients with mild to moderate disease, suffering from long standing post-COVID-19 syndrome. Taking in consideration, this pandemic is worldwide and still spreading, there's an urgent need for effective treatment for those patients who are suffering from the long standing, life debilitating, post-COVID-19 syndrome.

Neurologic signs and symptoms are common during hospitalization with COVID-19, with 42% of patients at onset of the disease and 82% during the course of the disease. Patients report mainly on myalgias, headaches, encephalopathy, dizziness, dysgeusia, and anosmia. After recovering from COVID-19, many patients continue to suffer from symptoms. Only 13% of the patients were completely free of symptoms after full resolution of the virus. The main symptom, reported by more than half the patients included cognitive impairment, fatigue and sleep disorders. A recent study analyzed data from 84,285 Individuals who recovered from suspected or confirmed COVID-19 showed reduced cognitive performance. This deficit scales with symptom severity and is evident amongst those without hospital treatment.

Two main biological sequelae of COVID-19 might play a role in the pathogenesis of this syndrome. The first is hypercoagulability state accompanies acute infection. This is characterized by increased risk of small and large vessel occlusion and is associated with increased mortality [9]. Neurologic complications might be a result of micro-infarcts in the central of peripheral nervous system; The second is an uncontrolled inflammatory response, called cytokines storm. This cytokine release is characterized by an increase in interleukin (IL)-1, IL-6, tumor necrosis factor (TNF)-α and a change in macrophages population. Thus, COVID-19 can cause neuroinflammation, that might be prolonged and lead to signs of post-COVID-19 syndrome.

The Micro-infarcts and neuroinflammation are important causes of local hypoxia, and specifically neurological hypoxia. One of the options to reverse hypoxia, reduce neuroinflammation and induce neuroplasticity is hyperbaric oxygen therapy (HBOT).

Hyperbaric oxygen therapy (HBOT) includes the inhalation of 100% oxygen at pressures exceeding 1 atmosphere absolute, thus enhancing the amount of oxygen dissolved in the body tissues. During HBOT, the arterial O2 tension typically exceeds 2000 mmHg, and levels of 200-400 mmHg occur in tissues Even though many of the beneficial effects of HBOT can be explained by improvement of tissue oxygenation, it is now understood that the combined action of hyperoxia and hyperbaric pressure, triggers both oxygen and pressure sensitive genes, resulting in inducing regenerative processes including stem cells proliferation and mobilization with anti-apoptotic and anti-inflammatory factors.

The HBOT protocol will be administrated in a multi-place chamber. The protocol includes 40 daily sessions, 5 sessions per week for two months. Treatment group will subjected to 100% oxygen by mask at 2 atmosphere (ATA) for 90 minutes with 5 minute air breaks every 20 minutes. Sham group will be subjected to 21% oxygen by mast for 90 minutes, at 1.2 ATA during the first five minutes of the session with the noise of circulating air, and then decrease slowly during the next five minutes to 1.03 ATA.

Inclusion Criteria:

1. Age above 18 years
2. Reported post COVID-19 cognitive deterioration that effect quality of life and persist at least 3 months after confirmed infection.
3. Subject willing and able to read, understand and sign an informed consent

Exclusion Criteria:

1. Inability to attend scheduled clinic visits and/or comply with the study protocol
2. History of traumatic brain injury (TBI) or any other non COVID brain pathology
3. Active malignancy
4. Substance use at baseline
5. Severe or unstable physical disorders or major cognitive deficits at baseline
6. HBOT for any reason prior to study enrolment
7. Chest pathology incompatible with pressure changes (including moderate to severe asthma)
8. Ear or Sinus pathology incompatible with pressure changes
9. An inability to perform an awake brain MRI
10. Active smoking