This might explain part of why the vast majority of patients are dying on ventilators(which uses forced air to increase O2 to the lungs) .
Hemoglobin is what transports that O2 to your bodies cells. If the coronavirus is destroying/depleting your hemoglobin, the extra O2 is not going to be captured efficiently.
https://en.wikipedia.org/wiki/Hemoglobin
Hemoglobin (American English) or haemoglobin (British English) (/ˈhiːməˌɡloʊbɪn, ˈhɛ-, -moʊ-/[1][2][3]), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein in the red blood cells (erythrocytes) of almost all vertebrates[4] (the exception being the fish family Channichthyidae[5]) as well as the tissues of some invertebrates. Hemoglobin in blood carries oxygen from the lungs or gills to the rest of the body (i.e. the tissues). There it releases the oxygen to permit aerobic respiration to provide energy to power the functions of the organism in the process called metabolism. A healthy individual has 12 to 20 grams of hemoglobin in every 100 ml of blood.
| hemoglobin | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| (heterotetramer, (αβ)2) | |||||||||||||
 Structure of human haemoglobin. α and β subunits are in red and blue, respectively, and the iron-containing heme groups in green. From PDB: 1GZX
ProteopediaHemoglobin | |||||||||||||
| Protein type | metalloprotein, globulin | ||||||||||||
| Function | oxygen-transport | ||||||||||||
| Cofactor(s) | heme (4) | ||||||||||||
| |||||||||||||
Hemoglobin (American English) or haemoglobin (British English) (/ˈhiːməˌɡloʊbɪn, ˈhɛ-, -moʊ-/[1][2][3]), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein in the red blood cells (erythrocytes) of almost all vertebrates[4] (the exception being the fish family Channichthyidae[5]) as well as the tissues of some invertebrates. Hemoglobin in blood carries oxygen from the lungs or gills to the rest of the body (i.e. the tissues). There it releases the oxygen to permit aerobic respiration to provide energy to power the functions of the organism in the process called metabolism. A healthy individual has 12 to 20 grams of hemoglobin in every 100 ml of blood.
In mammals, the protein makes up about 96% of the red blood cells' dry content (by weight), and around 35% of the total content (including water).[6] Hemoglobin has an oxygen-binding capacity of 1.34 mL O2 per gram,[7] which increases the total blood oxygen capacity seventy-fold compared to dissolved oxygen in blood. The mammalian hemoglobin molecule can bind (carry) up to four oxygen molecules.[8]
Hemoglobin is involved in the transport of other gases: It carries some of the body's respiratory carbon dioxide (about 20–25% of the total[9]) as carbaminohemoglobin, in which CO2 is bound to the heme protein. The molecule also carries the important regulatory molecule nitric oxide bound to a globin protein thiol group, releasing it at the same time as oxygen.[10]
"Despite the heterogeneity observed among the available studies, the results of this meta-analysis show that hemoglobin values are essentially reduced in COVID-19 patients with severe disease, compared to those with milder forms, thus confirming previous evidence garnered from patients with other types of pneumonia.9 Some clinical considerations can hence be made. First, initial assessment and longitudinal monitoring of hemoglobin values seems advisable in patients with the SARS-CoV-2 infection, whereby a progressive decrease in the hemoglobin concentration may reflect a worse clinical progression. Subsequently, studies shall be urgently planned to assess whether transfusion support (e.g., with administration of blood or packed red blood cells) may be helpful in this clinical setting to prevent evolution into severe disease and death."
There must be something more here because the medical experts would have to know this already but yet, we are not hearing about it, or treatments to try to boost hemoglobin levels.
Why is this not part of the treatment right now?
A close look at why this old malaria drug could be promising for COVID-19
https://www.asbmb.org/asbmb-today/science/032820/why-scientists-are-studying-if-chloroquine-could-t
"After a mosquito harboring the parasites bites a victim, the parasites make their way to the liver and eventually the red blood cells. Inside red blood cells, the parasites use the hemoglobin as a food source, which is digested in the parasite’s acidic food vacuole. The eventual destruction of red blood cells leads to life-threatening anemia. Consequently, malaria claims the lives of over 400,000 people per year, mostly children under the age of five in sub-Saharan Africa.
How chloroquine kills Plasmodium parasites has long been the subject of research. The drug is capable of binding to heme, which is a toxic byproduct of hemoglobin digestion. The parasite avoids the toxic effects of heme by stacking the molecules into an inert crystal called hemozoin. But when chloroquine binds to heme, hemozoin cannot be made, forcing the parasite to die in its own waste. Further supporting this idea is the fact that chloroquine concentrates in acidic cellular compartments, such as the parasite’s food vacuole.
But a virus is nothing like Plasmodium, begging the question of how chloroquine could possibly affect it. A virus is not even a cell — it is merely a small strand of DNA or RNA encapsulated in a bubble-like membrane of lipid and protein. After viruses invade, they co-opt the host cell’s machinery to reproduce themselves. They are the ultimate unwanted guest, depleting the host cell’s resources to make copies of themselves — virus babies, if you will."
"So how does chloroquine thwart coronavirus? When a virus replicates inside a host cell, its pieces get made and processed by the host cell’s manufacturing system. A major part of this protein processing center is a compartment called the Golgi apparatus, which releases those proteins within acidic vesicles called endosomes. Endosomes then deliver this protein cargo to other places, including the cell surface. Viruses can hijack this system to process and release their babies from the host cell. In addition, SARS CoV enters a host cell through an endosome vesicle formed from the host cell’s surface membrane.
Recall that chloroquine concentrates inside acidic cellular compartments. It can get into Plasmodium’s food vacuole, but it also concentrates inside a cell’s endosomes, which are used by viruses both when they enter and exit a host cell. Chemically, chloroquine is a weak base, sufficient to raise the pH in these compartments. As endosomes become less acidic, the proteins inside are ruined — they unfold because they are no longer at the correct pH. What this means for coronavirus is that its viral proteins are rendered nonfunctional because chloroquine changed the pH of the endosomes carrying them.
In addition to ruining the viral invader’s proteins, chloroquine can distort the shape of proteins called cytokines, which can reside in the endosomes of immune cells that fight infection. Sometimes, the immune system gets too excited and creates what is called a “cytokine storm,” which has been a major complication of COVID-19. By quelling this cytokine storm, chloroquine provides a dual advantage in helping the body combat coronavirus infection."