The most important thing I would recommend is to maintain the patients on a consistent photoperiod of light and darkness. In a hospital setting, the daily cycle can be 14 hours of ambient light and 10 hours of dark for example. The main thing to be avoided is constant or unnaturally long (>20hr) periods of light exposure or darkness (as well as photoperiods that vary arbitrarily from day to day). A consistent photoperiod within the normal range would insure that the circadian parameters of the immune response remain optimally entrained.

Thank you very much for your kind reply. "...thing to be avoided ... (>20hr) periods ...as well as photoperiods that vary arbitrarily from day to day ".

I agree with you, Sevag. Look, however, this perspective:

"Chronobiologists are often biased to think that the presence of a circadian rhythm is the preferred state. Here, we have identified an ambiguous situation with a testable hypothesis. Our alternative hypothesis is that supporting the circadian clock with zeitgebers will lead to entrainment and daily rhythms, and this in turn will lead to a better outcome. The null hypothesis would be that the presence of rhythms is an exacerbation and that the suppression of rhythms sometimes seen in serious illness is adaptive. These hypotheses could be tested descriptively via collection of continuous data from ICU stations and analysis for rhythmicity and appropriate entrained phase as correlated with outcome". Jeffrey Haspel, Minjee Kim, Phyllis Zee,..2021 "A Timely Call to Arms: COVID-19, the Circadian Clock, and Critical Care" (it is here in researchgate.net) .

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The hypothetical premise that the suppression of illness can be adaptive is certainly viable and worthy of investigation. In my own work in the past I have found, for example, that murine pluripotent embryonic stem cells cells, unlike MEFs, do not show transcriptional oscillation in a number of core clock genes. As such, it is conceivable that the suppression (or the absence) of circadian timekeeping can be desirable under specialized developmental (embryogenesis) and physiological (such as convalescence) settings.

Unless, however, the intention is to participate in a clinical trial that compares entrained and non-entrained paradigms in the recovery from viral infection, my recommendation would still be to maintain a consistent near-normal photoperiod for the convalescing patients. Predictability of the circadian phase in the patients would at least still allow the body to engage diversory mechanisms that can suspend peripheral oscillators in order to (presumably) optimize immune response, whereas "forcing" arrhythmicity, if the null hypothesis is incorrect, could result in unnecessary decrements in recovery and/or survival.

i think it related to decrease inflammatory mediator, regulate with awake and sleep cycle, it had mainly central effect on brain which regulate hormone.

I think inside the brain peace are necessary. Cells at night clean our CNS, do it by astrocytes, and eliminate toxics sustances and excessive activation of neurons. So, controlling the clycle and rhythmicity will be very necessary. Remember that neurons, astrocytes and oligodendroglia develpmed from ectodermic embryon and, such as skin do, they can respond more or less to light. So much light will be bad, but necessary and so much night too. In our evolution, light and dark, was implanted in our genes and, as a monkey, we are awake in the morning with light and sleep at night. We need it.

Yes, Prof-Drs.-Researchers Soraya Valles, Shimaa Mohamed, Sevag Kaladchivachi and kind readers...

...it seems to be important to rescue the natural rhythms of the patient in the ICU to probably facilitate recovery. I understand that in other medical conditions, they appear to be still somewhat active (https://www.researchgate.net/publication/314239086_Significance_of_circadian_rhythms_in_severely_brain-injured_patients_A_clue_to_nessconscious).

Being able to non-invasively record the circadian signals in the patient can also be useful when applying these stimulations in the appropriate phase or in order to discover adaptive rhythms, if any.

...think of therapeutic methods to avoid having to use respirators. Perhaps by (somehow) increasing oxygen intake to the blood (using intravenous oxygen administration, Preprint An Alternative to Ventilators to Support Critical COVID-19 Patients

Gang Pan * 1 Tao Lyu, John A. Hunt School of Animal, Rural, and Environmental Sciences, Nottingham Trent University, Brackenhurst Campus NG25 0QF, Southwell, UK [email protected] (G.P). This method seems very invasive, ??however, not sure).

Thanks all for the comments, clicks and interest.