1. ards/pneumonia caused by other viral infections (positive for other virus) 2. ards/pneumonia caused by other non-viral infections or trauma 3. known pregnancy or positive pregnancy test in women of childbearing age 4. patients with previous lung fibrosis more than 10% 5. ct- or spirometry-verified severe copd with emphysema 6. contraindication for hbo according to local guidelines 7. not likely to need icu admission \< 7 days of screening (subjective criteria that may exclude any patients that fulfil the other inclusion criteria but where the treating physician suspect a spontaneous recovery) 8. mental inability, reluctance or language difficulties that result in difficulty understanding the meaning of study participation 9. prisoner (exclusion criteria according to irb at ucsd)

1. ards/pneumonia caused by other viral infections (positive for other virus) 2. ards/pneumonia caused by other non-viral infections or trauma 3. known pregnancy or positive pregnancy test in women of childbearing age 4. patients with previous lung fibrosis more than 10% 5. ct- or spirometry-verified severe copd with emphysema 6. contraindication for hbo according to local guidelines 7. not likely to need icu admission \< 7 days of screening (subjective criteria that may exclude any patients that fulfil the other inclusion criteria but where the treating physician suspect a spontaneous recovery) 8. mental inability, reluctance or language difficulties that result in difficulty understanding the meaning of study participation 9. prisoner (exclusion criteria according to irb at ucsd)

ards/pneumonia caused by other viral infections (positive for other virus) ards/pneumonia caused by other non-viral infections or trauma known pregnancy or positive pregnancy test in women of childbearing age patients with previous lung fibrosis more than 10% ct- or spirometry-verified severe copd with emphysema contraindication for hbo according to local guidelines not likely to need icu admission < 7 days of screening (subjective criteria that may exclude any patients that fulfil the other inclusion criteria but where the treating physician suspect a spontaneous recovery) mental inability, reluctance or language difficulties that result in difficulty understanding the meaning of study participation prisoner (exclusion criteria according to irb at ucsd)

ards/pneumonia caused by other viral infections (positive for other virus) ards/pneumonia caused by other non-viral infections or trauma known pregnancy or positive pregnancy test in women of childbearing age patients with previous lung fibrosis more than 10% ct- or spirometry-verified severe copd with emphysema contraindication for hbo according to local guidelines not likely to need icu admission < 7 days of screening (subjective criteria that may exclude any patients that fulfil the other inclusion criteria but where the treating physician suspect a spontaneous recovery) mental inability, reluctance or language difficulties that result in difficulty understanding the meaning of study participation prisoner (exclusion criteria according to irb at ucsd)

1. ards/pneumonia caused by other viral infections (positive for other virus) 2. ards/pneumonia caused by other non-viral infections or trauma 3. known pregnancy or positive pregnancy test in women of childbearing age 4. patients with previous lung fibrosis more than 10% 5. ct- or spirometry-verified severe copd with emphysema 6. contraindication for hbo according to local guidelines 7. not likely to need icu admission < 7 days of screening (subjective criteria that may exclude any patients that fulfil the other inclusion criteria but where the treating physician suspect a spontaneous recovery) 8. mental inability, reluctance or language difficulties that result in difficulty understanding the meaning of study participation 9. prisoner (exclusion criteria according to irb at ucsd)

1. ards/pneumonia caused by other viral infections (positive for other virus) 2. ards/pneumonia caused by other non-viral infections or trauma 3. known pregnancy or positive pregnancy test in women of childbearing age 4. patients with previous lung fibrosis more than 10% 5. ct- or spirometry-verified severe copd with emphysema 6. contraindication for hbo according to local guidelines 7. not likely to need icu admission < 7 days of screening (subjective criteria that may exclude any patients that fulfil the other inclusion criteria but where the treating physician suspect a spontaneous recovery) 8. mental inability, reluctance or language difficulties that result in difficulty understanding the meaning of study participation 9. prisoner (exclusion criteria according to irb at ucsd)